CHAPTER 21
Heating, Ventilating,
and Air-Conditioning
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Heating, ventilating, and air-conditioning (HVAC) is the
terminology used to refer to the industry that deals with the
heating and air-conditioning equipment and systems found in a
building. The HVAC system is also referred to as the mechanical
system of the building, providing heat, fresh or conditioned
air, and ventilation. The HVAC system is installed in a building to
regulate temperature. This includes the furnace, air-conditioning
equipment, and duct systems, which ensure the uniform
transfer of the cold, hot, and filtered air throughout the building.
Conditioned refers to a heated or cooled space. The duct system
is square, rectangular, and round sheet metal pipes or plastic
used to conduct hot or cold air from the HVAC system.
air is required, the return air passes over the surface of
a cooling coil. Finally, the conditioned air is picked up
again by the fan and the air cycle is repeated. Figure 21-1
shows the air cycle in a forced-air system. Conditioned
air is air that has been heated, cooled, humidified, or
dehumidified to maintain an interior space within the
desired comfort zone. The comfort zone is the range
of temperatures, humidity, and air velocities at which
people generally feel comfortable.
SUPPLY OUTLET
SUPPLY DUCT
The International Residential Code (IRC) requires a
heating unit to be installed in any residence built in
an area where the winter design temperature is below
60°F (16°C). Unless you are designing a home in
Hawaii, plan for a heating unit capable of producing
and maintaining a room temperature of 68°F (20°C) at
a point 3' (914 mm) above the floor and 2' (610 mm)
from exterior walls for all habitable rooms. Portable
space heaters cannot be used to meet compliance with
the current IRC codes. Refer to Chapter 9 for additional code requirments.
CENTRAL FORCED-AIR SYSTEMS
One of the most common systems for heating and
air-conditioning circulates the air from living spaces
through or around heating or cooling devices. A fan
forces the air into sheet metal or plastic pipes called
ducts, which connect to openings called diffusers, or
air-supply registers. Warm air or cold air passes through
the ducts and registers to enter the rooms, heating
or cooling them as needed. Air then flows from the
room through another opening into the return duct, or
return-air register. The return duct directs the air from
the rooms over the heating or cooling device. If warm
air is required, the return air is passed over the surface
of either a combustion chamber, which is the part of a
furnace where fuel is burned, or a heating coil. If cool
FAN
HEATING
OR
COOLING
COIL
FILTER
RETURN DUCT
RETURN OUTLET
A
RETURN OUTLET
RETURN DUCT
FAN
FILTER
HEATING
OR
COOLING
COIL
SUPPLY DUCT
SUPPLY OUTLET
B
FIGURE 211 (A) Downdraft forced-air system heated air cycle.
(B) Updraft forced-air system heated air cycle.
485
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Architectural Drafting and Design
The Heating Cycle
If the air cycle previously described is used for heating,
the heat is generated in a furnace. Furnaces for residential heating produce heat by burning fuel oil or natural
gas, or by using electric heating coils or heat pumps.
If the heat comes from burning fuel oil or natural gas,
the combustion (burning) takes place inside a combustion chamber. The air to be heated does not enter the
combustion chamber but absorbs heat from the outer
surface of the chamber. The gases given off by combustion are vented through a vent pipe or chimney. In an
electric furnace, the air to be heated is passed directly
over the heating coils. This type of furnace does not
require a vent pipe or chimney.
CONDENSER
EXPANSION VALVE
EVAPORATOR
COOL
AIR
OUT
WARM
AIR IN
WARM
AIR
OUT
FAN
COMPRESSOR
FIGURE 212 Schematic diagram of a refrigeration cycle.
The Cooling Cycle
If the air from the room is to be cooled, it is passed over
a cooling coil. The most common type of residential
cooling system is based on two principles:
1. As liquid changes to vapor, it absorbs large amounts
of heat.
2. The boiling point of a liquid can be changed by
changing the pressure applied to the liquid. This is
the same as saying that the temperature of a liquid
can be raised by increasing its pressure and can be
lowered by reducing its pressure.
Common refrigerants boil (change to a vapor) at very
low temperatures, some as low as 21°F (6°C), which is
below freezing.
The principal parts of a refrigeration system are the
cooling coil (evaporator), the compressor, the condenser, and the expansion valve. Figure 21-2 shows a
diagram of the cooling cycle. The cooling cycle operates
as follows: Warm air from the ducts is passed over the
evaporator. As the cold liquid refrigerant moves through
the evaporator coil, it picks up heat from the warm air.
As the liquid picks up heat, it changes to a vapor. The
heated refrigerant vapor is then drawn into the compressor, where it is put under high pressure. This pressure
raises the temperature of the vapor even more.
Next, the high-temperature, high-pressure vapor
passes to the condenser, where the heat is removed.
This is done by blowing air over the coils of the condenser. The high-pressure vapor changes to a liquid as
the condenser removes heat. From the condenser, the
refrigerant flows to the expansion valve. As the liquid
refrigerant passes through the valve, the pressure is
reduced, lowering the temperature of the liquid still
further, so that it is ready to pick up more heat.
The cold low-pressure liquid then moves to the evaporator. The pressure in the evaporator is low enough to
allow the refrigerant to boil again and absorb more heat
from the air passing over the coil of the evaporator.
FORCED-AIR HEATING PLANS
Complete plans for the heating system are normally
needed when applying for a building permit or a
mortgage loan, depending on the requirements of the
local building department or the lending agency. If a
complete heating layout is required, it can be prepared
by the architectural drafter, a heating contractor, or a
mechanical engineer.
When forced-air electric, gas, or oil heating systems
are used, the warm-air outlets and return-air locations
can be shown, as in Figure 21-3. Notice the registers are
normally placed in front of a window so warm air is circulated next to the coldest part of the room. As the warm
air rises, a circulation action is created as the air goes
through the complete heating cycle. Cold-air returns are
often placed in the ceiling or floor at a central location.
A complete forced-air heating plan shows the size,
location, and number of Btu dispersed to the rooms
from the warm-air supplies. Btu stands for British thermal unit, which is a measure of heat. The location and
size of the cold-air return and the location, type, and
output of the furnace are also shown.
The warm-air registers are sized in inches or millimeters. For example, 4" × 12" (100 × 300 mm). The size
of the duct is also given, as shown in Figure 21-4. The
note 20/24 means a 20" × 24" (500 × 600 mm) register;
a number 8 next to a duct means an 8" (200 mm)
diameter duct. Millimeters are used for metric values.
Chapter 21: Heating, Ventilating, and Air-Conditioning
487
4 X 12 WA
125 CFM
FAMILY
4 X 12 WA
125 CFM
4 X 10 WA
100 CFM
UTILITY
DINING
17'-0" X 11'-5"
4 X 10 WA
100 CFM
9'-5" X 7'-1"
17'-4" X 11'-5"
SHOP
24 X 10 RA
12'-6" X 11'-5"
BATH
LIVING
KITCHEN
12'-11" X 15'-4"
12'-9" X 15'-4"
GARAGE
22'-5" X 23'-4"
4 X 12 WA
125 CFM
6"Ø WA(TOE KICK)
100 CFM
ENTRY
DW
GD
TC
LS
COVERED PORCH
MAIN FLOOR HVAC
A
SCALE: 1/4" = 1'-0"
4 X 10 WA
100 CFM
2 X 10 WA
75 CFM
4 X 12 WA
125 CFM
BED#2
10'-10" X 11'-5"
4 X 10 WA
100 CFM
BATH
STORAGE
16'-10" X 11'-2"
FURN
BED#1
12'-11" X 19'-3"
BATH
2 X 10 WA
75 CFM
4 X 12 WA
125 CFM
BED#3
PARTY
12'-5" X 14'-10"
10'-10" X 11'-9"
2 X 10 WA
75 CFM
4 X 10 WA
100 CFM
B
UPPER FLOOR HVAC
SCALE: 1/4" = 1'-0"
C
LOWER FLOOR HVAC
SCALE: 1/4" = 1'-0"
FIGURE 213 Simplified forced-air HVAC plan of the (A) main floor, (B) upper floor, and (C ) partial basement for the model home
represented throughout this textbook.
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Architectural Drafting and Design
FAMILY
4 X 12 WA
125 CFM
4 X 12 WA
125 CFM
4 X 10 WA
100 CFM
UTILITY
DINING
17'-0" X 11'-5"
4 X 10 WA
100 CFM
9'-5" X 7'-1"
17'-4" X 11'-5"
SHOP
12'-6" X 11'-5"
24 X 10 RA
12"Ø SUPPLY UP FROM
CRAWL TO ATTIC SPACE
BATH
LIVING
KITCHEN
12'-11" X 15'-4"
12'-9" X 15'-4"
GARAGE
22'-5" X 23'-4"
4 X 12 WA
125 CFM
6"Ø WA(TOE KICK)
100 CFM
ENTRY
DW
GD TC
LS
COVERED PORCH
MAIN FLOOR HVAC
A
SCALE: 1/4" = 1'-0"
4 X 10 WA
100 CFM
2 X 10 WA
75 CFM
4 X 12 WA
125 CFM
BED#2
6"Ø
10'-10" X 11'-5"
6"Ø
BATH
8"Ø
7"Ø
10"Ø
12"Ø
6"Ø
BED#1
12'-11" X 19'-3"
6"Ø
BATH
6"Ø
2 X 10 WA
75 CFM
BED#3
10'-10" X 11'-9"
2 X 10 WA
75 CFM
4 X 10 WA
100 CFM
B
UPPER FLOOR HVAC
SCALE: 1/4" = 1'-0"
FIGURE 214 Detailed forced-air HVAC plan of the (A) main floor, (B) upper floor, and (C) partial basement for the model home
represented throughout this textbook.
Chapter 21: Heating, Ventilating, and Air-Conditioning
489
7"Ø UP
STORAGE
7"Ø UP
6"Ø UP
7"Ø
6"Ø
6"Ø UP
16'-10" X 11'-2"
4 X 10 WA
100 CFM
7"Ø
FURNACE
75,000 BTU
8"Ø
16" X 10"
12" X 8"
24" X 10"
7"Ø
4 X 12 WA
125 CFM
7"Ø
6"Ø
PARTY
6"Ø
12"Ø SUPPLY UP
TO ATTIC SPACE
6"Ø
GARAGE ABOVE
12'-5" X 14'-10"
7"Ø UP
C
6"Ø UP
LOWER FLOOR HVAC
SCALE: 1/4" = 1'-0"
FIGURE 214 Continued
This same system can be used as a central cooling
system when cool air is forced from an air conditioner
through the ducts and into the rooms. WA means warm
air, and RA is return air. CFM is cubic feet per minute,
which is the rate of airflow.
Forced-air plans are discussed again later in this
chapter as related to making heating and cooling thermal calculations.
Providing Duct Space
The use of a duct space called a chase was introduced
in Chapter 18 when laying out the floor plans. When
ducted heating and cooling systems are used, the location of the ducts often becomes a serious consideration.
The ducts are placed in a crawl space or attic when possible. When ducts cannot be confined to a crawl space
or attic, they must be run inside the occupied areas of
the home or building. The designer and building contractor try to conceal ducts when they must be placed
in locations where they could be seen. There are several
ways to conceal ducts.
When ducts run parallel to structural members,
the ducts can be placed within the space created by
the structural members. This is referred to as running the ducts in the joist space, rafter space, or stud
space. These terms identify the type of construction
members used. This works when the duct size is equal
to or smaller than the size of the construction members. In the case of return-air ducts, the construction
members and enclosing materials can be used as the
duct plenum. A plenum is a chamber that can serve
as a distribution area for heating or cooling systems,
generally between a false ceiling and the actual ceiling,
or between construction members. When a duct can
be in a space created between construction members,
no extra framing needs to be done to conceal the
ducts. When ducts must be exposed to occupied areas,
they are normally enclosed by framing covered with
gypsum or other finish material. When ducts are run
in an area such as an unfinished basement, it is possible to leave them exposed.
When possible, ducts are run in the ceiling of a
hallway, because they can be framed and finished with
a lowered ceiling. The minimum ceiling height in hallways can be 7'−0" (2134 mm). Bathrooms and kitchens can also have a minimum ceiling height of 7'−0"
(2134 mm), though this is normally undesirable. The
typical ceiling height in habitable rooms is approximately 8' (2440 mm), but a ceiling can be as low as
7'−6" (2286 mm) for at least 50% of the room, with no
portion less than 7'−0" (2134 mm). This information
is valuable, because it tells you how low ceilings can be
framed down to provide space for ducts when needed.
490
Architectural Drafting and Design
When running ducts along a ceiling, wall framing must
be designed higher to still maintain adequate floor-toceiling height.
When ducts must be run vertically between floors,
they need to be run in an easily concealed location, such
as in a closet or in the stud space. The stud space can be
used for ducts that are 3 1/2" deep for 2 × 4 (50 × 100 mm)
studs, 5 1/2" deep for 2 × 6 (50 × 150 mm) studs, or
7 1/2" deep for 2 × 8 (50 × 200 mm) studs. If the duct
can be run up through a closet, then it can be framed in
and covered in a chase. A chase is a continuous recessed
area built to carry or conceal ducts, pipes, or other construction products. If the duct cannot be located in a
convenient place for concealment, then it might need
to be framed into the corner of a room; however, this
is normally not preferred. The framing for the chase in
Figure 21-4 is shown on the floor plan as a wall surrounding the duct to be concealed, and is located in a
portion of the kitchen pantry. A note is usually placed
that indicates the use, such as
CHASE FOR 12 X 12 RETURN DUCT.
HOT WATER SYSTEMS
In a hot water system, the water is heated in an oil- or
gas-fired boiler and then circulated through pipes to
radiators or convectors in the rooms. The boiler is supplied with water from the fresh water supply for the
house. The water is circulated around the combustion
chamber, where it absorbs heat.
In one kind of system, one pipe leaves the boiler
and runs through the rooms of the building and back
to the boiler. In this one-pipe system, the heated water
leaves the supply, is circulated through the outlet, and is
returned to the same pipe, as shown in Figure 21-5. In a
two-pipe system, two pipes run throughout the building.
CONVECTION OUTLETS
BOILER
FIGURE 215 One-pipe hot water system.
CONVECTION OUTLETS
SUPPLY MAIN
RETURN
MAIN
BOILER
FIGURE 216 Two-pipe hot water system.
One pipe supplies heated water to all of the outlets. The
other is a return pipe, which carries the water back to the
boiler for reheating, as shown in Figure 21-6.
Hot water systems use a pump, called a circulator, to
move water through the system. The water is kept at
a temperature between 150°F and 180°F (65.5°C and
82°C) in the boiler. When heat is needed, the thermostat starts the circulator, which supplies hot water to the
convectors in the rooms. The thermostat is described
later in this chapter.
HEAT PUMP SYSTEMS
A heat pump is a forced-air central heating and cooling
system that operates using a compressor and a circulating refrigerant system. Heat is extracted from the outside air and pumped inside the building. The heat pump
supplies up to three times as much heat per year for the
same amount of electrical consumption as a standard
electric forced-air heating system. In comparison, this
can result in a 30% to 50% annual energy saving. In the
summer, the cycle is reversed, and the unit operates as
an air conditioner. In this mode, the heat is extracted
from the inside air and pumped outside. On the cooling cycle the heat pump also acts as a dehumidifier.
Figure 21-7 shows how a heat pump works.
Residential heat pumps vary in size from 2 tons
to 5 tons. Some vendors carry two-stage heat pumps
that alternate between 3 tons and 5 tons, for example.
During minimal demand, the more efficient 3-ton
phase is used, and the 5-ton phase is operable during
peak demand. Each ton of rating removes approximately 12,000 Btu per hour (Btuh) of heat.
Residential or commercial buildings that, because
of their size or design, cannot be uniformly heated or
cooled from one compressor can require a split system
Chapter 21: Heating, Ventilating, and Air-Conditioning
COOLING CYCLE
COIL
BLOWER
FAN
COMPRESSOR
OUTDOOR UNIT
WARM COIL
BLOWER
COIL
HEATING CYCLE
491
FAN
COMPRESSOR
INDOOR UNIT
COOL COIL
OUTDOOR UNIT
INDOOR UNIT
FIGURE 217 Heat pump heating and cooling cycle. Courtesy Lennox Industries, Inc.
with two or more compressors. The advantage of such
an arrangement can be that two smaller units more
effectively control the needs of two zones within the
building.
Other features, such as an air cleaner, a humidifier, or
an air freshener, can be added to the heat pump system.
In general, the initial cost of the heat pump is about
twice as much as a conventional forced-air electric heat
system. However, the advantages and long-range energy
savings make it a significant option for heating. The cost
difference is less if cooling is a requirement.
The total heat pump system uses an outside compressor, an inside blower to circulate air, a backup heating
coil, and a complete duct system. Heat pump systems
move a large volume of air; therefore, the return air and
supply ducts must be adequately sized. Figure 21–8
shows the relationship between the compressor and the
rest of the system. The compressor should be placed in
FIGURE 218 Heat pump compressor. Courtesy Lennox
Industries, Inc.
a location where some noise does not cause a problem.
The compressor should be placed on a concrete slab
about 36" × 48" × 6" (900 × 1200 × 150 mm) in size
in a location that allows adequate service access. Do
not connect the concrete slab to the building to avoid
transmitting vibration. Show or note the concrete slab
on the foundation plan. Verify the vendor’s specifications for exact concrete slab dimensions. Heat pumps
may not be as efficient in some areas of the country as in
other areas because of annual low or high temperatures.
Verify the product efficiency with local heating and
cooling contractors.
ZONE CONTROL SYSTEMS
A zoned heating system requires one heater and one
thermostat per room. No duct work is required, and only
the heaters in occupied rooms need to be turned on.
One of the major differences between a zonal and
a central system is flexibility. A zonal heating system
allows the occupant to determine how many rooms
are heated, how much energy is used, and how much
money is spent on heat. A zonal system allows the home
to be heated to the family’s needs, whereas a central
system requires using all the heat produced. If the airflow is restricted, the efficiency of the central system is
reduced. There is also a 10% to 15% heat loss through
ductwork in central systems.
Regardless of the square footage in a house, its
occupants normally use less than 40% of the entire
area on a regular basis. A zoned system is very adaptable to heating the 40% of the home that is occupied.
Automatic controls allow for night setback, day setback,
and unheated areas to be controlled as needed. The
home owner can save as much as 60% on energy costs
through controlled heating systems.
492
The two types of zone heaters are baseboard and
fan. Baseboard heaters have been the most popular type
for zoned heating systems for the past several decades.
They are used in many different climates and under
various operating conditions. No ducts, motors, or fans
are required. Baseboard units have an electric heating
element, which causes a convection current as the air
around the unit is heated. A convection current is a
natural condition where warm air rises and cool air
falls. The heated air rises into the room and is replaced
by cooler air that falls to the floor. Baseboard heaters
should be placed on exterior walls under or next to windows or other openings. These units do project a few
inches into the room at floor level. Some home owners
do not care for this obstruction, in comparison with the
floor duct vent of a central system or the recessed wallmounted fan heater. Furniture arrangements should be
a factor in locating any heating element, because furniture must be kept a safe distance from the heater.
Fan heaters are generally mounted in a wall recess.
A resistance heater is used to generate heat, and a fan
circulates the heat into the room. These units should
be placed to circulate the warmed air in each room
adequately. Avoid placing the heaters on exterior walls,
as a recessed unit reduces or eliminates insulation. The
fan in these units causes some noise.
Split systems using zonal heat in part of the home
and central heat in the rest of the home are also possible.
This is also an option for additions to homes that have a
central system. In a building addition, zoned heat can be
used effectively so the central system is not overloaded
and need not be replaced.
RADIANT HEAT
Radiant heating and cooling systems provide a comfortable environment by controlling surface temperatures and minimizing excessive air motion within the
space. Warm ceiling panels are effective for winter
heating because they warm the floor surfaces and
glass surfaces by direct transfer of radiant energy. The
surface temperature of well-constructed and properly
insulated floors is 2°F to 3°F (−16.4°C) above the
ambient air temperature, and the inside surface temperature of glass is increased significantly. Ambient
temperature is the temperature of the air surrounding
a heating or cooling device. As a result of these heated
surfaces, downdrafts are minimized to the point where
no discomfort is felt.
Radiant heat systems yield annual operating cost savings of 20% to 50%, compared with conventional convective systems. This savings is accomplished through
Architectural Drafting and Design
lower thermostat settings and through the superior,
cost-effective design found in radiant heating products.
It is generally accepted that 3% to 4% of the energy
cost is saved for each degree that the thermostat is
lowered. Users of surface-mounted radiant panels take
advantage of this fact in two ways. First, they are able
to achieve comfort at a lower ambient air temperature,
normally 60°F to 64°F (16.6°C) as compared with convection heating air temperatures of 68°F to 72°F (21°C).
Second, they are able to practice comfortable day and
night temperature setback of about 58°F in areas used
frequently, 55°F (12.8°C) in areas used occasionally,
and 50°F (10°C) in seldom-used areas.
Radiant heat can be achieved with oil- or gas-heated
hot water piping in the floor or ceiling, to electric
coils, wiring, or elements either in or above the ceiling gypsum board, and transferred to metal radiator
panels generally mounted by means of a bracket about
1" (25 mm) below the ceiling surface.
Zone-radiant heating panels are an alternative when
space is limited or the location of built-in zone heaters
is a factor.
THERMOSTATS
A thermostat is an automatic mechanism for controlling the amount of heating or cooling given by a central
or zonal heating or cooling system. The thermostat floor
plan symbol is shown in Figure 21-9.
The location of the thermostat is important to the
proper function of the system. For zoned heating or
cooling units, thermostats can be placed in each room,
or a central thermostat panel that controls each room
can be placed in a convenient location. For central heating and cooling systems, there can be one or more thermostats, depending on the layout of the system or the
number of units required to service the building. For
example, a very large home or office building can have
a split system that divides the building into two or more
zones, each individual zone with its own thermostat.
Several factors contribute to the effective placement
of the thermostat for a central system. A good common
location is near the center of the building and close to
a return-air duct for a central forced-air system. The
air entering the return-air duct is usually temperate,
thus causing little variation in temperature on the
T
FIGURE 219 Thermostat floor plan symbol.
Chapter 21: Heating, Ventilating, and Air-Conditioning
thermostat. A key to successful thermostat placement is
to find a stable location where an average temperature
reading can be achieved. There should be no drafts that
adversely affect temperature settings. The thermostat
should not be placed in a location where sunlight or
a heat register causes an unreliable reading. The same
rationale suggests that a thermostat not be placed close
to an exterior door, where temperatures can change
quickly. Thermostats should be placed on inside partitions rather than on outside walls that could lead to false
temperature readings. Avoid placing the thermostat
near stairs or a similar traffic area, where significant
bouncing or shaking could cause the mechanism to
alter the actual reading.
Energy consumption can be reduced by controlling
thermostats in individual rooms. Central panels are
available that make it easy to lower or raise temperatures in any room where each panel switch controls
one remote thermostat.
Programmable microcomputer thermostats effectively help reduce the cost of heating or cooling. Some
units automatically switch from heat to cool while
minimizing temperature deviation from the setting
under varying load conditions. These computers can
be used to alter heating and cooling temperature settings automatically for different hours of the day, days
of the week, or months of the year.
493
include the atmosphere, steam from cooking and
showers, and individuals, who can produce up to
1 gallon (3.8 liters) of water vapor per day.
●
Incomplete combustion from gas-fired appliances
or wood-burning stoves and fireplaces can generate
a variety of pollutants, including carbon monoxide,
aldehydes, and soot. Carbon monoxide is a colorless,
odorless, poisonous gas, produced by incomplete
burning of carbon-based fuels. Aldehydes are very
reactive organic compounds that contribute to ozone
production. Soot is finely divided carbon deposited
from flames during the incomplete combustion of
organic substances such as coal.
●
Humans and pets can transmit bacterial and viral
diseases through the air.
●
Tobacco smoke adds chemical compounds to the air
that can affect smokers and nonsmokers alike.
●
Formaldehyde, when present, is considered a factor
in the cause of eye irritation, certain diseases, and
respiratory problems. Formaldehyde is a chemical
found in disinfectants, preservative, carpets, furniture, and the glue used in construction materials,
such as plywood and particleboard, as well as some
insulation products.
●
Radon is a naturally occurring radioactive gas that
breaks down into compounds that are carcinogenic
(cancer-causing) when large quantities are inhaled
over a long period of time. Radon can be more
apparent in a building containing large amounts of
concrete or in certain areas of the country. Radon
can be monitored scientifically at a nominal cost,
and barriers can be built that help reduce concern
about radon contamination. Radon monitoring and
control are discussed later in this chapter.
●
Household products such as those available in aerosol spray cans and craft materials such as glues and
paints can contribute a number of toxic pollutants.
HEAT RECOVERY AND VENTILATION
A heat recovery and ventilation (HRV) system is also
referred to as a heat exchanger, air exchanger, or
air-to-air heat exchanger. A heat recovery ventilation
system is a ventilation system that uses a counter flow
heat exchanger between the inbound and outbound
airflow. HRVs provide fresh air and improved climate
control, while also saving energy by reducing the heating or cooling needs of the home. Energy recovery
ventilators (ERV) are closely related; however, ERVs
also transfer the humidity level of the exhaust air to
the intake air.
Sources of Pollutants
Air pollution in a building is a principal reason for
installing a heat recovery and ventilation system. A
number of sources contribute to an unhealthy environment within a home or business:
●
Moisture in the form of relative humidity can cause
structural damage as well as health problems, such
as respiratory problems. Sources of relative humidity
Air-to-Air Heat Exchangers
Government energy agencies, architects, designers,
and contractors around the country have been evaluating construction methods that are designed to reduce
energy consumption. Some of the tests have produced
super-insulated, vapor-barrier-lined, airtight buildings. The result has been a dramatic reduction in heating and cooling costs. However, the air quality in these
houses has been significantly reduced and can be harmful to health. An airtight building does not breathe,
so stale air and pollutants have no place to escape.
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Architectural Drafting and Design
Heat passes from the outgoing to the incoming
airstream through thin metal or plastic sheets.
(Only one sheet shown for clarity.)
CORE
FAN
Fresh, warmed
air supply
to house
FRESH, DRY, COLD
OUTSIDE AIR
Warm, moist, stale,
polluted return
air from house
COOLED, STALE
EXHAUST AIR
TO THE OUTSIDE
FAN
Moisture in house air reaches “dew point” and
condenses when cooled by losing heat to the
incoming airstream.
CONDENSATE
DRAIN TO SEWER
Pollution stays in the outgoing airstream
and is exhausted to the outside. (It does not
pass through the heat exchanger core sheets.)
FIGURE 2110 Components and function of an air-to-air heat exchanger. Courtesy U.S. Department of Energy.
Air-to-air heat exchanger technology is a way to avoid
this problem. In the past, the air in a building was
exchanged in leakage through walls, floors and ceilings, and around openings. Although this random leakage was no insurance that the building was properly
ventilated, it did ensure a certain amount of heat loss.
Now, with the concern for energy conservation, it is
clear that the internal air quality of a home or business
cannot be left to chance.
An air-to-air heat exchanger is a heat recovery
and ventilation device that pulls polluted, stale,
warm air from the living space and transfers the heat
in that air to fresh, cold air being pulled into the
house. Heat exchangers do not produce heat; they
only exchange heat from one airstream to another.
The heat transfer takes place in the core of the heat
exchanger, which is designed to avoid mixing the
two airstreams and to ensure that indoor pollutants
are removed. Moisture in the stale air condenses in
the core and is drained from the unit. Figure 21-10
shows the function and basic components of an airto-air heat exchanger.
The recommended minimum effective air exchange
rate is 0.5 air changes per hour (ach). Codes in some
areas of the country have established a rate of 0.7 ach.
The American Society of Heating, Refrigeration, and
Air-Conditioning Engineers, Inc. (ASHRAE) recommends ventilation levels based on the amount of air
entering a room. The recommended amount of air
entering most rooms is 10 cubic feet per minute (cfm).
The rate for kitchens is 100 cfm, and bathrooms is
50 cfm. Mechanical exhaust devices vented to outside air should be added to kitchens and baths to
maintain the recommended air exchange rate.
The minimum heat exchanger capacity needed for
a building can be determined easily. Assume a 0.5 ach
rate in a 1500 sq ft single-level, energy-efficient house
and follow these steps:
STEP 1 Determine the total floor area in square feet. Use
the outside dimensions of the living area only.
30 × 50 ft = 1500 sq ft
Determine the total volume within the house in
cubic feet by multiplying the total floor area by the
ceiling height.
STEP 2
1500 sq ft × 8 sq ft = 12,000 cu ft
Determine the minimum exchanger capacity
in cfm by first finding the capacity in cubic feet per
hour (cfh). To do this, multiply the house volume in
cubic feet by the ventilation rate in air changes per
hour (ach).
STEP 3
12,000 cu ft × 0.5 ach = 6000 cfh
Convert the cfh rate to cubic feet per minute by
dividing the cfh rate by 60 minutes.
STEP 4
6000 cfh ÷ 60 min = 100 cfm
There is a percentage of capacity loss due to mechanical resistance that should be considered by the system
designer.
Most home owners are not knowledgeable about
potential air pollution and how internal air can be adequately controlled by ventilation. Therefore, the architect
designing an energy-efficient home must plan the proper
ventilation. The ducts, intake, and exhaust for such a
system should be located on the advice of a ventilation
consultant or a knowledgeable HVAC contractor.
Chapter 21: Heating, Ventilating, and Air-Conditioning
495
EXHAUST SYSTEMS: CODE
REQUIREMENTS
Exhausts are part of the HVAC system. Exhaust systems
are required to remove odors, steam, moisture, and pollutants from inside a building. The following are basic
general code requirements that need to be considered
during the design process.
●
●
●
●
●
Range hoods must be vented to the outside by a
single-wall galvanized or stainless steel, or copper
duct. This duct shall have a smooth inner surface, be
substantially airtight, and have a backdraft damper.
A damper is a movable plate that regulates the draft
or airflow in a chimney or vent pipe. A backdraft
damper has blades that are activated by gravity,
permitting air to pass through them in one direction only.
Metal or noncombustible range hoods cannot be any
closer than 24" (610 mm) to the range.
Clothes dryer vents must be independent of all
other systems and carry the moisture outside. The
vent cannot be connected with screws that extend
into the vent. Exhaust vents need a backdraft
damper. The vent duct should be rigid metal 0.016"
(0.406 mm) thick with a smooth inside and joints
running in the direction of the airflow. Approved
flexible duct can be used but cannot be concealed
within the construction.
A 4" (100 mm) clothes dryer duct cannot be longer
than 25" (7620 mm) from the dryer to the wall
or roof vent and must have a full opening exhaust
hood. The total length should be reduced by 2'–6"
(762 mm) for each 45° bend and 5' (1524 mm) for
each 90° bend.
When gas clothes dryers are installed in a closet, they
must be approved for such use, and no other fuelburning appliance can be in the same closet.
CENTRAL VACUUM SYSTEMS
Central vacuum systems have a number of advantages over portable vacuum cleaners. These advantages
include:
●
●
●
●
●
Affordability; some systems cost no more than a
major appliance.
Increased resale value of home.
Removal of dirt too heavy for most portable units.
Exhaust of dirt and dust out of the house or office.
No motor unit or electric cords; however, there are
often long hoses.
FIGURE 2111 Vacuum wall outlet. Courtesy Vacu-Maid, Inc.
V
FIGURE 2112 Vacuum outlet floor plan symbol.
●
●
●
Less noise.
Savings in cleaning time.
Ability to vary vacuum pressure.
A well-designed system requires only a few inlets to
cover an entire home or business, including exterior
use. The hose plugs into a wall outlet and the vacuum
is ready for use, as shown in Figure 21-11. The hose is
generally lightweight; without a portable unit to carry,
it is often easier to vacuum in hard-to-reach places. The
central canister empties easily to remove dust and debris
from the house or business. The floor plan symbol for
vacuum cleaner outlets is shown in Figure 21–12. The
central unit can be located in the garage or storage area
and shown as a circle labeled CENTRAL VACUUM
SYSTEM.
HVAC SYMBOLS
More than a hundred HVAC symbols can be used in
residential and commercial heating plans. Only a few
of the symbols are typically used in residential HVAC
drawings. Figure 21-13 shows some common HVAC
symbols.
496
Architectural Drafting and Design
EQUIPMENT SYMBOLS
EXPOSED RADIATOR
FLUSHED ENCLOSED
RADIATOR
RECESSED RADIATOR
UNIT VENTILATOR
PLAN
UNIT HEATER
(PROPELLER)-PLAN
PRESSURE-REDUCING
VALVE
DUPLEX STRAINER
STEAM
PROJECTING
ENCLOSED RADIATOR
UNIT HEATER
(CENTRIFUGAL)-PLAN
AIRLINE VALVE
STRAINER
S
PRESSURE GAUGE
AND CLOCK
THERMOMETER
AUTOMATIC
3-WAY VALVE
RELIEF VALVE
AUTOMATIC
2-WAY VALVE
DUCTWORK
FD
12X20
DUCT (1ST FIGURE, WIDTH;
2ND FIGURE, DEPTH)
FLEXIBLE
CONNECTION
DIRECTION
OF FLOW
VD
MANUAL
VOLUME DAMPER
T
INCLINED RISE IN RESPECT
TO AIRFLOW
WALL SUPPLY
OUTLET
FLOOR SUPPLY
OUTLET
AD
FIRE DAMPER
WITH ACCESS DOOR
R
4 X 10
75 CFM
4 X 12
100 CFM
AUTOMATIC
VOLUME DAMPER
DUCTWORK WITH
ACOUSTICAL LINING
SOLENOID VALVE
PLAN
CANVAS
CONNECTOR
THERMOSTAT
D
14 X 20
DUCT DIRECTION OF FLOW
AND SIZE FACE X DEPTH
INCLINED DROP IN
RESPECT TO AIRFLOW
HEATER
SURFACE MOUNT
12 X 20
700 CFM
14 X 20
14 X 20
OUTSIDE AIR DUCT
SIZE FACE X WIDTH
EXHAUST OR RETURN
SUPPLY DUCT
SECTION
10"
75 CFM
TURNING VANES
FLOOR REGISTER
FAN AND MOTOR
WITH BELT GUARD
20" CD
1000 CFM
4 X 10
75 CFM
CEILING SUPPLY
OUTLET
96X6 - LD
400 CFM
HEATER RECESSED
CEILING DIFFUSER
SUPPLY OUTLET
20 X 14 CD
700 CFM
20 X 12 - L
700 CFM
CEILING DIFFUSER
SUPPLY OUTLET
LOUVER OPENING
DEFLECTING
DAMPER
HEAT TRANSFER SURFACE
(RADIANT HEAT)
HEATING PIPING
MPS
MPS
HIGH PRESSURE
STEAM
MEDIUM PRESSURE
STEAM
BD
VPD
BOILER
BLOW OFF
CONDENSATE OR VACUUM
LPS
HPR
HIGH PRESSURE
RETURN
LOW PRESSURE
STEAM
PPD
FEEDWATER PUMP
DISCHARGE
FOR
FOV
A
FUEL OIL
RETURN
FUEL OIL
VENT
COMPRESSED
AIR
MPR
MEDIUM
PRESSURE RETURN
LPR
LOW PRESSURE
RETURN
MU
V
FOS
MAKE UP
WATER
AIR RELIEF
LINE
FUEL OIL
SUCTION
HW
HWR
HOT WATER HEATING HOT WATER HEATING
SUPPLY
RETURN
AIR-CONDITIONING PIPING
RL
REFRIGERANT
LIQUID
RD
REFRIGERANT
DISCHARGE
RS
CWS
REFRIGERANT
SUCTION
CONDENSER WATER
SUPPLY
CHWR
MU
H
D
CHILLED WATER
RETURN
MAKE-UP
WATER
HUMIDIFICATION
LINE
DRAIN
FIGURE 2113 Common HVAC symbols.
CWR
CONDENSER WATER
RETURN
CHWS
CHILLED WATER
SUPPLY
Chapter 21: Heating, Ventilating, and Air-Conditioning
497
REFRIGERATION SYMBOLS
H
CAPILLARY
TUBE
SHELL AND COIL
CONDENSER
WATER COOLED
EXPANSION JOINT
COMPRESSOR
FORCED AIR
FINNED CONDENSER
AIR COOLED
PLATE COILS
HEADERED OR MANIFOLD
EVAPORATOR
FLOAT VALVE,
LOW SIDE
FLOAT VALVE,
HIGH SIDE
P
AIR ELIMINATOR
LINE FILTER
HANGER
PA
GAUGE
ANCHOR
EVAPORATOR,
FINNED TYPE,
NATURAL CONVECTION
COOLING
TOWER
COMBINATION
STRAINER AND DRYER
EVAPORATIVE
CONDENSER
HEAT EXCHANGER
SIGHT GLASS
IMMERSION
COOLING UNIT
T
PRESSURE
SWITCH
THERMOSTAT,
SELF-CONTAINED
THERMAL BULB
PRESSURE SWITCH
EVAPORATOR,
FORCED CONVECTION
EXPANSION VALVE,
HAND
SCALE TRAP
AIR-COOLED
CONDENSING UNIT
EXPANSION VALVE,
AUTOMATIC
EXPANSION VALVE,
THERMOSTATIC
DRYER
FILTER AND
STRAINER
WATER-COOLED
CONDENSING UNIT
FIGURE 2113 Continued
UNIVERSAL HVAC DESIGN
The following are a few issues that can be considered in
designing a building for people with disabilities.
●
Thermostats. The thermostat should be placed
between 36" and 48" (915 to 1220 mm) high. Use
the higher distance or a protective cover if children
are present. Thermostats are available with graduations printed in Braille or large digital numbers for
●
people with visual impairments. Some are available with clicks so the user can feel or hear the
movement.
Heating systems. Electric forced-air furnaces or
heat pumps may be preferred by people with disabilities. However, place floor registers in places
out of the traffic pattern or place them 90° to
the wall so wheelchairs can cross easily. Electric
radiant heat is a consideration for people with
498
allergies. Install an electronic air filter if forcedair systems are used. An auxiliary ceiling heater
with a timer can be placed in a bathroom to heat
the space.
HVAC CODE REQUIREMENTS
The purpose of the National Energy Conservation
Code is to regulate the design and construction
of the exterior envelope and selection of HVAC;
service water heating; electrical distribution and
illuminating systems; and equipment required for
effective use of energy in buildings for human
occupancy. The exterior envelope is made up of elements of a building that enclose conditioned spaces
through which thermal energy transfers to or from
the exterior.
The following are general code requirements for
some common heating and cooling equipment and duct
systems. Specific applications and installations must be
confirmed with the exact code regulations and manufacturer specifications.
Heating and Cooling Equipment
●
●
●
●
●
●
●
Heating and cooling equipment located in a garage
must be protected from impact by automobiles. This
is generally done by placing a steel pipe embedded in
concrete in front of the equipment.
Fixed appliances need to be fastened in place.
Heating and cooling equipment should be located
with clearances to allow access for servicing and
replacement of the largest piece of equipment. This
overrides minimum requirements.
A door or access at least 20" (508 mm) or large
enough to remove the largest piece of equipment
must be provided to access the equipment location.
An unobstructed working space not less than 30"
(762 mm) wide and high should be provided next to
the control side of the equipment.
When equipment is located in an attic, a passageway
at least 22" (559 mm) wide by 30" (762 mm) high
must be provided from the attic access to the equipment and controls.
An electrical outlet and lighting fixture should be
provided near the equipment and have a switch at
the doorway or access.
Equipment located in a crawl space must have access
and a passageway not less than 20" (508 mm) wide
by 30" (762 mm) high.
Architectural Drafting and Design
●
●
●
●
●
●
●
●
Equipment located on the ground should be supported on a concrete slab and be at least 3" (76 mm)
above the ground.
Suspended equipment must be at least 6" (153 mm)
from the ground.
When equipment is placed in an excavated (dug-out)
area, there must be at least 12" (305 mm) on the
sides and 30" (762 mm) in front of the controls.
Excavations deeper than 12" (305 mm) need to have
a concrete or masonry wall extending 4" (102 mm)
above the adjoining ground.
Equipment installed outdoors must be listed and
labeled for such use.
Fuel-burning warm-air furnaces should not be
installed in a room designed for use as a storage closet.
Furnaces located in a bedroom or bathroom must be
installed in a sealed enclosure so that combustion air
will not be taken from the living space. Combustion air
is air provided at a burner for proper combustion.
Direct-vent furnaces are not required to be in an
enclosure.
Fuel-burning warm-air furnaces must be supplied
with combustion air.
Return air should be taken from inside the dwelling
and can be mixed with outside air. Return air cannot
be taken from kitchens, bathrooms, garages, or other
dwelling units. Outside air should not be taken from
within 10" (3048 mm) of an appliance or plumbing
vent outlet that is located less than 3" (914 mm)
above the air inlet.
Duct Systems
●
●
●
●
●
Equipment connected to duct systems must have a
250°F (121°C) temperature limit control.
Galvanized steel ducts should be ASTM A 525
specification.
Metal ducts need the following thicknesses:
❍ Round or rectangular enclosed: 14" or less, 0.016"
thick; over 14", 0.021" thick.
❍ Rectangular exposed: 14" or less, 0.021" thick;
over 14", 0.022" thick.
Factory-made ducts must be approved for installation
and have the UL label and compliance. As described
earlier, UL is the abbreviation for Underwriters
Laboratories, Inc., which tests and labels products for
approved uses.
Gypsum products can be used as ducts if the air temperature does not exceed 125°F (52°C) and there is
no condensation.
Chapter 21: Heating, Ventilating, and Air-Conditioning
●
●
●
●
●
●
●
●
Spaces between structural members can be used as
return ducts if they are isolated from other spaces
with tight-fitting sheet metal or wood at least 2"
(51 mm) thick.
Underground duct systems must be constructed of
approved concrete, clay, metal, or plastic.
Duct coverings and linings need to have a flamespread rating not greater than 25 and a smoke-development rating not more than 50, and must withstand
a test temperature of at least 250°F (121°C).
Insulated ducts should have a minimum thermal
resistance value of R 4.2. Insulate ducts in unconditioned areas.
Exterior ducts must have a weatherproof covering.
Joints and seams should be made substantially
airtight.
Metal ducts must be supported by 18-gauge metal
straps or 12-gauge galvanized wire spaced no more
than 10' (3048 mm) apart and must be at least 4"
(102 mm) from the ground. Nonmetallic ducts can
be supported to the manufacturer’s specifications.
Crawl spaces used as a supply plenum cannot have
gas lines or plumbing cleanouts, should be clean of
loose combustible material, and must be airtight. The
ground should be covered with a 4-mil (0.102-mm)
moisture barrier, and the space shall be formed by
materials with a flame-spread rating of no more than
200. A plenum is an enclosed duct or area that is connected to a number of branch ducts.
THERMAL CALCULATIONS
FOR HEATING/COOLING
Thermal calculations are necessary to establish the
correct furnace, ductwork, supply, and return register
specifications for HVAC designs. Thermal calculations
for heating and cooling are usually performed by a
mechanical engineer or a professional HVAC contractor. Computer software applications are available that
allow the designer to input specific information about
the building, such as square footage, volume, exterior
walls, and openings. Many HVAC companies make
manual calculations using the steps provided in this
content, or similar steps.
The History of Estimating Heat Loss
The basic method for estimating residential heat loss
today has been in use since the early 1900s. Historically,
the primary use was to calculate the design heat load
of houses in order to estimate the size of gas and oil
499
heating systems required. Because home designers,
builders, and heating system installers did not want
to receive complaints from cold home owners, they
commonly designed the heating system for worst-case
weather conditions, with a bias toward overestimating
the design heat load to ensure that the furnace would
never be too small. Consequently, many gas and oil
furnaces were too large.
As early as 1915, an engineer for a gas utility began
modifying the design heat load with a degree day method
to estimate annual energy consumption. Oil companies
also began using this method to predict when to refill
their customers’ oil tanks. A degree day is a measure that
gauges the amount of heating or cooling needed for a
building using 65° as a baseline. Data from this period,
for houses with little or no insulation, indicated that the
relationship between annual heating energy requirements and average outside temperature began at 65°F
(18°C) in homes. This was the beginning of the 65°F
base for degree days. Studies made by the American
Gas Association up to 1932 and by the National District
Heating Association in 1932 also indicated that a 65°F
base was appropriate for houses of the period.
Experience in the 1950s and early 1960s with electrically heated homes indicated that the traditional degree
day procedure overestimated annual heating loads. This
was due primarily to tighter, better insulated houses
with balance temperatures below 65°F, and to the use
of more appliances. These later studies led to a modified
degree day procedure incorporating a modifying factor,
C. This C factor compensates for such things as higher
insulation levels and more heat-producing appliances
in the house. The high insulation levels found in homes
built to current codes, and those that have been retrofitted with insulation, cause even lower balance temperatures than those of houses built in the 1950s and 1960s.
This history has been adapted from Standard Heat Loss
Methodology, Bonneville Power Administration.
HVAC Terminology
Many terms are unique to the HVAC industry. It is
important to be familiar with key HVAC terminology
to help you understand this chapter and communicate
effectively. The following terms are commonly associated with HVAC applications:
Btu (British thermal unit): A unit of measure
determined by the amount of heat required to raise
1 pound of water 1 degree Fahrenheit. Heat loss is
calculated in Btu per hour (Btuh).
Compass point: The relationship of the building to compass orientation. In referring to cooling
500
calculations, it is important to evaluate the amount of
glass in each wall as related to compass orientation.
This is due to the differences effected by solar gain.
Solar gain is also known as solar heat gain or passive
solar gain, which refers to the increase in temperature in a building that results from solar radiation.
Duct loss: Heat loss through ductwork in an unheated
space, which has an effect on total heat loss. Insulating
those ducts helps increase efficiency.
Grains: The amount of moisture in the air, calculated
by the grains of moisture in 1 cubic foot. A grain is
a unit of weight. Air at different temperatures and
humidities holds different amounts of moisture. The
effect of this moisture content becomes more of a
factor in the southern and midwestern states than in
other parts of the country.
Heat transfer multiplier: The amount of heat that
flows through 1 square foot of the building surface. The result depends on the type of surface and
whether it is applied to heating or cooling.
Indoor temperature: The indoor design temperature
is generally 60°F to 70°F.
Indoor wet bulb: Relates to the use of the wet-bulb
thermometer inside. A wet-bulb thermometer is one
in which the bulb is kept moistened and is used to
determine the humidity level.
Infiltration: The inward flow of air through a porous
wall or crack. In a loosely constructed home, infiltration substantially increases heat loss. Infiltration
around windows and doors is calculated in cfm per
linear foot of crack. Window infiltration greater than
.5 cfm per linear foot of crack is excessive.
Internal heat gain: Heat gain associated with factors
such as heat transmitted from appliances, lights,
other equipment, and occupants.
Latent load: The effects of moisture entering the
building from the outside by humidity infiltration or
from the inside, produced by people, plants, and daily
activities such as cooking, showers, and laundry.
Mechanical ventilation: Amount of heat loss through
mechanical ventilators such as range hood fans or
bathroom exhaust fans.
Outdoor temperature: Related to average winter and
summer temperatures for a local area. If the outdoor winter design temperature is 20°F (−7°C), this
means that the temperature during the winter is 20°
or higher 97.5% of the time. If the outdoor summer
design temperature in an area is 100°F (38°C), this
means that the temperature during the summer is
100° or less 97.5% of the time. Values for each area
Architectural Drafting and Design
of the country have been established by ASHRAE.
Verify the outdoor temperature with your local
building department or heating contractor.
Outdoor wet bulb: Relates to the use of a wet-bulb
thermometer outside.
R-factor: Resistance to heat flow. The more resistance
to heat flow, the higher the R-value. For example,
3 1/2" of mineral wool insulation has a value of R-11
and 6" of the same insulation has a value of R-21. R is
equal to the reciprocal of the U-factor, 1/U = R.
Sensible load calculations: Load calculations associated with temperature change that occurs when a
building loses or gains heat.
Temperature difference: The indoor temperature
less the outdoor temperature.
U-factor: The coefficient of heat transfer expressed in
Btuh ft2/°F of surface area.
STEPS IN FILLING OUT THE
RESIDENTIAL HEATING DATA SHEET
The model home main floor plan, upper floor plan, and
partial basement plan shown in Figure 21-14 are used
for the calculations of total heat loss. The completed
residential heating data sheet, shown in Figure 21-15,
is a two-page data sheet divided into several categories
with calculations resulting in total heat loss for the
model home. The large numbers alongside the categories refer to the following steps, used in completing the
form. Notice that the calculations are rounded off to the
nearest whole unit.
Outdoor temperature: Use the recommended
outdoor design temperature for your area. The area
selected for this problem is Dallas, Texas, with an
outdoor design temperature of 22°F (−6°C), which
has been rounded off to 20°F to make calculations
simple to understand. The proper calculations would
interpolate the tables for a 22°F outdoor design
temperature.
STEP 2 Indoor temperature: 70°F (21°C).
STEP 3 Temperature difference:
STEP 1
70° − 20° = 50°F (10°C)
Movable glass windows: Select double glass;
find area of each window (frame length × width);
then combine for total: 292 sq ft.
STEP 5 Btuh heat loss: Using 50°F design temperature difference, find 46 approximate heat transfer
multiplier:
STEP 4
46 × 292 = 13,432 Btuh
Chapter 21: Heating, Ventilating, and Air-Conditioning
61'-0"
1"
9'-82
38'-0"
17'-6"
5'-113
4"
17'-4"
3'-2"
5'-61
4"
6'-0"
1"
13'-32
8'-8"
B
3"
6'-64
1"
4'-82
5'-0"
8'-8"
A
C
3"
6'-84
C
UP 1'-6"
C
H
G
13
BATH
DN 7 1/2"
1"
2'-32
34" RAIL
UP 1'-2"
ENTRY
12'-9" X 15'-4"
GARAGE
22'-5" X 23'-4"
LINE OF 7'-0" CLG
DW
GD TC
RANGE & HOOD W/ FAN,
VENT TO OUTSIDE AIR
LS
12'-4"
2
5/8" TYPE 'X' GYP BD FROM
FLOOR TO BOT OF ROOF SHTHG
KITCHEN
S&P
CLOSET
5
1"
3'-52
12'-11" X 15'-4"
UP 14R
5'-8"
4" BRICK VENEER
LIVING
10
HVAC CHASE
3
36'-0"
7
1"
3'-92
1"
1'-12
3'-6"
LINE OF 7'-0" CLG
3'-7"
6'-0"
34" RAIL
DN 14R
3
28'-0"
15'-10"
36'-0"
LINE OF UPPER
FLOOR
4'-9"
23'-8"
3'-6"
DN 7 1/2"
22" X 30"
ATTIC ACCESS
4
1'-0"
2'-0"
3'-6"
1"
1'-62
11'-8"
5'-0"
SHOP
12'-6" X 11'-5"
17'-4" X 11'-5"
FLUSH HEARTH
PANTRY
12'-2"
4'-51
4"
DINING
9'-5" X 7'-1"
4" CONC
FLATWORK TYP
SCREEN CLOSEABLE
VENT WITHIN 24" OF
FIREBOX
17'-0" X 11'-5"
UTILITY
1"
7'-102
FAMILY
BARBECUE
1"
8'-62
SEE FDTN PLAN FOR
FIREPLACE LOCATION
G
3"
6'-54
6'-111
4"
3"
7'-84
A
UP 1'-6"
3"
3'-74
1"
11'-42
13'-5"
G
2
1"
6'-62
6'-8"
10'-0"
LINE OF
UPPER FLOOR
6'-0"
8'-0"
2'-0"
1
A
B
1"
13'-22
COVERED PORCH
(2) 4" X 4"
POSTS
14
B
14
A
16'-0"
11'-0"
11'-0"
SQUARE FOOTAGE
C
6'-0"
11'-0"
38'-0"
23'-0"
6'-0"
MAIN FLOOR
UPPER FLOOR
LOWER FLOOR
TOTAL LIVING AREA
GARAGE
GENERAL NOTES
1.
61'-0"
MAIN FLOOR PLAN
SCALE: 1/4" = 1'-0"
N
1352 SQ FT
1148 SQ FT
448 SQ FT
2948 SQ FT
556 SQ FT
2.
3.
ALL PENETRATIONS IN TOP OR BOTTOM
PLATES FOR PLUMBING OR ELECTRICAL RUNS
TO BE SEALED. SEE ELECTRICAL PLANS FOR
ADDITIONAL SPECIFICATIONS.
PROVIDE 1/2" WATERPROOF GYPSUM BOARD
AROUND ALL TUBS, SHOWERS, AND SPAS.
VENT DRYER AND ALL FANS TO OUTSIDE AIR
THRU VENT WITH DAMPER.
501
FIGURE 2114 Sample floor plans for heat loss and heat gain calculations. The floor plans shown here are for the model house used throughout this textbook.
502
Architectural Drafting and Design
1"
38'-32
1"
17'-82
11'-7"
9'-0"
5'-83
4"
6'-0"
3'-43
4"
5'-71
4"
1"
5'-82
1"
5'-102
B
A
D
F
3'-0"
3'-8"
1" 1'-91"
3'-52
2
1"
6'-62
HVAC CHASE
11
4
6'-3"
22" X 30"
ATTIC ACCESS
11
CLOSET
S&P
S&P
CLOSET
4
5
S&P
12
S&DBL P
10'-0"
7
WALK-IN
CLOSET
5
1" 6
3'-92
BATH
1"
6'-22
30" WIDE
KNEE SPACE
3'-0"
E
9
36" FIBERGLASS
SHOWER OVER
1/2" GYP BD
BED#3
10'-10" X 11'-9"
24" X 24" DBL
INSULATED TEMP
GLASS SKYLIGHT
6'
FIBERGLASS
SPA
S&P
G
E
B
A
3"
2'-104
7'-10"
30'-0"
36" RAIL
DN 14R
30'-0"
34" RAIL
4
1" 2'-31"
2'-32
2
24" X 36" OPENABLE
INSULATED TEMP
GLASS SKYLIGHT
10'-10" X 11'-5"
1"
2'-52
5'-10"
20'-0"
BED#2
4
LINEN
BED#1
12'-11" X 19'-3"
5' FIBERGLASS
TUB/SHOWER OVER
1/2" WP GYP BD
BATH
12'-2"
D
J
13'-3"
3"
5'-114
4'-0"
1"
9'-42
2'-71
4"
9'-6"
4'-9"
6'-10"
11'-7"
1"
38'-32
UPPER FLOOR PLAN
SCALE: 1/4" = 1'-0"
FIGURE 2114 Continued
Sliding glass doors: Select double glass; find
total area of 34 sq ft.
STEP 7 Btuh heat loss:
STEP 6
34 × 48 = 1632 Btuh
Doors: Weather-stripped solid wood; 2 doors at
39 sq ft.
STEP 9 Btuh heat loss:
STEP 8
39 × 30 = 1170 Btuh
Walls: Excluding garage; perimeter in running
feet 341 × ceiling height 8' = gross wall area 2728 sq
ft. Subtract window and door areas: 2728 sq ft − 365
sq ft = net wall area 2363 sq ft.
STEP 11 Frame wall: No masonry wall above or below
grade. This does not apply to the model house. The
model house has masonry veneer on the front, but
this requirement relates to a solid masonry wall.
When there is masonry wall, subtract the square
footage of masonry wall from total wall for the net
frame wall. Fill in net amount on approximate insulation value; 2363 sq ft frame wall, R-713. (Although
R-13 is given in this example, the typical code is
R-19. Confirm codes with Chapter 9.)
STEP 12 Btuh heat loss:
2363 × 3.5 = 8270 Btuh
STEP 10
No masonry above grade in this building.
STEPS 1516 No masonry below grade in this building.
STEP 17 Heat loss subtotal: Add together results from
Steps 5, 7, 9, and 12; sum is 21,775 Btuh. Transfer
the amount to the top of page 2 of the form.
STEPS 1314
Chapter 21: Heating, Ventilating, and Air-Conditioning
503
18'-2"
17'-6"
8"
4 PIECE WINDOW WELL
WELLCRAFT 5600 12" GRAVEL
BELOW WINDOW WELL GRADE TYP
8"
STORAGE
6'-61
4"
16'-10" X 11'-2"
ROUGH IN FOR STORAGE
TANK FOR SOLAR WH
1"
6'-61
3'-92
4"
WH
FURN
WINDOW SCHEDULE
MARK
A
SIZE
1'-0" X 5'-0"
TYPE
TEMPERED
ROUGH
-
QUAN
2
B
8'-0" X 5'-0"
W4N5 CSM
8'-2 3/4" X 5'-5 7/8"
1
C
4'-0" X 5'-0"
W2N5 CSM
4'-2 1/4" X 5'-5 7/8"
2
D
4'-0" X 3'-6"
W2N3 CSM
4'-2 1/4" X 3'-5 1/2"
2
E
3'-6" X 3'-6"
2N3 CSM
3'-5 1/4" X 3'-5 1/2"
2
F
6'-0" X 4'-0"
G64 SLDG
6'-0 1/2" X 4'-0 1/2"
1
G
5'-0" X 3'-6"
G536 SLDG
5'-0 1/2" X 3'-6 1/2"
4
H
4'-0" X 3'-6"
G436 SLDG
4'-0 1/2" X 3'-6 1/2"
1
J
4'-0" X 2'-0"
A41 AWN
4'-0 1/2" X 2'-0 5/8"
1
K
4'-0" X 4'-0"
G42 SLDG
4'-0 1/2" X 4'-0 1/2"
3
PARTY
12'-5" X 14'-10"
2 X 4 DFPT STUDS
8"
3"
4'-24
K
UP 14R
6'-6"
5/8" TYPE 'X' GYP BD
UNDER ALL USABLE
AREA UNDER STAIRS
DOOR SCHEDULE
5
34" RAIL
K
7'-0"
26'-8"
3'-111
4"
8
15'-2"
28'-0"
5'-11"
11'-6"
K
WORKBENCH
5'-7"
8"
B
5 1/2" WIDE CONC LEDGE
FOR BRICK VENEER
B
MARK
1
SIZE
3'-0" X 6'-8"
TYPE
SC RP METAL INSULATED
QUAN
1
2
3'-0" X 6'-8"
SC RP FLUSH METAL INSUL
2
3
2'-8" X 6'-8"
SC
2
4
2'-8" X 6'-8"
HC
6
5
2'-6" X 6'-8"
HC
4
6
2'-6" X 6'-8"
POCKET
1
7
2'-4" X 6'-8"
POCKET
2
8
PR 2'-6" X 6'-8"
HC
1
9
5'-0" X 6'-0"
BI-PASS
1
10
3'-0" X 6'-8"
BI FOLD
1
11
3'-6" X 6'-8"
BI-FOLD
2
1
12
3'-0" X 6'-0"
SHATTER PROOF
13
6'-0" X 6'-8"
WOOD FRAME TEMP SLDG GL
1
14
9'-0" X 7'-0"
OVERHEAD GARAGE
2
WALL AREAS (EXCLUDING BASEMENT)
8"
17'-6"
WINDOWS
8"
SKYLIGHTS
DOORS
18'-2"
TOTAL OPENINGS
LOWER FLOOR PLAN
% OPENINGS
3249 SQ FT
286.6 SQ FT
10 SQ FT
67.4 SQ FT
354 SQ FT
11%
SCALE: 1/4" = 1'-0"
FIGURE 2114 Continued
Ceiling: R-30 insulation (given), same square
footage as floor plan 976 sq ft (given).
STEP 19 Btuh heat loss:
STEP 18
976 × 1.6 = 1562 Btuh
Floor over an unconditioned space: R-19 insulation (given), 97 sq ft.
STEP 21 Btuh heat loss:
STEP 20
976 × 2.6 = 2538 Btuh
STEPS 2223
Basement floor: Does not apply to this
house.
Concrete slab without perimeter system:
Does not apply to this house.
STEPS 2627 Concrete slab with perimeter system:
Does not apply to this house.
STEP 28 Infiltration/ventilation: 976 sq ft floor × 8 ft
ceiling height = 7808 cu ft:
STEPS 2425
0.40 × 7808 cu ft ÷ 60 = 52 cfm
Infiltration = mechanical ventilation
cfm = fresh air intake
STEP 29
Btuh heat loss:
52 × 55 = 2860 Btuh
Heat loss subtotal: Add results from Steps 17,
19, 21, and 29; sum is 28,735 Btuh.
STEP 31 Duct loss: R-4 insulation (given); determine
15% of value from Step 30:
STEP 30
0.15 × 28,735 = 4310
When no ducts are used, exclude this item.
Total heat loss: Add items from Steps 30 and
31; sum is 33,045 Btuh.
STEP 32
504
Architectural Drafting and Design
FIGURE 2115 Completed residential heating data sheet form. Base data sheet form courtesy Lennox Industries, Inc.
Chapter 21: Heating, Ventilating, and Air-Conditioning
FIGURE 2115 Continued
505
506
Architectural Drafting and Design
STEPS IN FILLING OUT THE
RESIDENTIAL COOLING DATA SHEET
Figure 21–16 is a completed residential cooling data
sheet. The two-page data sheet is divided into several categories, with calculations resulting in total
sensible and latent heat gain for the model home
shown in Figure 21–14. The large numbers by each
category refer to the following steps used in completing the form.
Outdoor temperature: 100°F (38°C).
STEP 2 Indoor temperature: 70°F (21°C).
STEP 3 Temperature difference:
STEP 1
Sensible heat gain subtotal: Add together
items from Steps 5, 9, 13, 25, 28; 19,056 Btuh heat
gain. Transfer the amount to the top of page 2 of the
form.
STEP 32 Ceiling: R-30 insulation; 976 sq ft.
STEP 33 Btuh heat gain:
STEP 31
976 × 1.7 = 1659 Btuh
Floor over unconditioned space: R-19 insulation; 976 sq ft.
STEP 35 Btuh heat gain:
STEP 34
976 × 1.2 = 1171 Btuh
100° − 70° = 30°F (38°C − 21°C = 17°).
STEP 36
Glass, no shade: Double-glazed.
STEP 4 North glass: Including sliding glass door;
172 sq ft.
STEP 5 Btuh heat gain:
976 sq ft × 8 ft = 7808 cu ft
STEPS 413
172 × 28 = 4816 Btuh
NE and NW glass: None; house faces N,
E, W, S.
STEP 8 West glass: 48 sq ft.
STEP 9 48 × 78 = 3,744 Btuh.
STEPS 1011 SE and SW glass: None; house faces N,
E, W, S.
STEP 12 South glass: 98 sq ft.
STEP 13 Btuh heat loss:
STEPS 67
Infiltration/ventilation:
0.40 × 7808 cu ft ÷ 60 = 52 cfm
STEP 37
Btuh heat gain:
52 × 32 = 1664 Btuh
Internal heat gain: Number of people (assume
4 for this house) 4 × 300 Btuh per person = 1200
Btuh. Kitchen allowance given 1200 Btuh.
STEP 39 Sensible heat gain subtotal: Add together items
from Steps 31, 33, 35, 37, and 38; sum is 24,750
Btuh.
STEP 40 Duct gain:
STEP 38
24,750 × 0.15 = 3713 Btuh
Total sensible heat gain: Add together items
from Steps 39 and 40; sum is 28,463 Btuh.
STEPS 4245 Latent load calculations.
STEP 42 Determine the local relative humidity conditions, either wet, medium, medium dry, or dry. Our
selected location is medium, which is 35 grains.
STEP 43 Latent load infiltration:
STEP 41
98 × 43 = 4214 Btuh
Glass inside shade: This house is sized
without considering inside shade. If items from Steps
14–23 are used, omit items from Steps 4–13.
STEP 24 Doors: Solid wood weather-stripped, 2 doors;
39 sq ft.
STEP 25 Btuh heat gain:
STEPS 1423
39 × 9.6 = 374 Btuh
STEP 26
Walls (excluding garage walls):
0.68 × 35 grains = 52 cfm (from Step 36) = 1238 Btuh
STEP 44
Latent load ventilation:
0.68 × 35 grains × 52 cfm = 1238 Btuh
Latent load people:
341 × 8 ft = 2728 sq ft − 365 sq ft = 2363 sq ft net wall area
STEP 45
Frame wall: 2363 sq ft.
STEP 28 Btuh heat gain:
4 people × 230 Btuh = 920 Btuh
STEP 27
2363 × 2.5 = 5908 Btuh
STEPS 2930
house.
Masonry wall above grade: None in this
Total latent heat gain: Add together items from
Steps 43, 44, and 45; sum is 3396 Btuh.
STEP 47 Total sensible and latent heat gain: Add
together items from Steps 41 and 46; sum is 31,859
Btuh.
STEP 46
Chapter 21: Heating, Ventilating, and Air-Conditioning
FIGURE 2116 Completed residential cooling data sheet form. Base data sheet form courtesy Lennox Industries, Inc.
507
508
FIGURE 2116 Continued
Architectural Drafting and Design
GOING
GREEN
509
Improving Indoor Air Quality
The content for this Going Green feature is taken in
part from Mascord Efficient Living, Building a Sustainable
Lifestyle.
CLEANING THE AIR
A variety of design alternatives and environmental
applications can be used to improve indoor air quality.
This discussion includes features that can be designed
into a home to achieve better air quality, and daily
applications that occupants can use to continue to
improve the environment.
Ventilation and Air Filtration
Air movement in and out of the home needs to be
controlled for maximum efficiency. In order to achieve
desired air movement control, it is important to seal the
envelope tightly and control ventilation properly.
An HVAC professional contractor can properly
calculate the amount of air required for ventilation in
the home design. This professional takes into account all
the variables associated with properly sizing ventilation
equipment, which includes the number of bathroom and
kitchen fans, regional air pressure, size of indoor spaces,
and proper heating and cooling equipment selection. To
maintain adequate fresh air, the ventilation system may
include heat recovery to regularly change the air within
the home. This ensures that you always breathe fresh air
while maintaining a high level of energy efficiency by
exchanging energy from outgoing air to incoming air.
The air used to ventilate a home comes from the
outside, and is subjected to external pollutants. The
air should run through a filtering system in order to
protect the occupants from airborne pollutants. There
are various types of air filters including MERV and HEPA
filters. MERV stands for Minimum Efficiency Reporting
Value, which refers to the filtration efficiency of an air
filter. Performance is determined by comparing airborne
particle counts upstream and downstream of the air
filter. HEPA stands for High Efficiency Particle Arresting.
HEPA filters are designed to be 99.97% effective in
capturing particles as small as 0.3 microns. When
designing the HVAC system, it is important to confirm
that all HVAC equipment is compatible.
Ultraviolet Light Systems
Certain ultraviolet (UV) light can be beneficial for
improving indoor air quality. Ultraviolet energy is
measured in nanometers. UV wavelengths are shorter
than visible light, and are invisible to the human eye.
One of the wavelengths of ultraviolet light is the C
bandwidth. This desirable UV-C light has a wavelength
of 253.7 nanometers, which is called the germicidal
bandwidth. The home can have germs, mold, bacteria,
toxins, and gases that cause unhealthy air conditions.
These contaminants can pass through the forced air
heating and cooling system several times per hour,
making the furnace a collection point for recirculating
air. This makes the ductwork, near the furnace, an ideal
place to install an indoor air cleaning system to control
harmful levels of indoor air pollutants. UV-C lights are
mounted inside the ductwork between the furnace filter
and the exchangers for the furnace and air-conditioning.
The furnace fan circulates air across the UV-C light,
neutralizing up to 98% the microorganisms. Exposure
to UV-C light can destroy or damage microorganisms by
disrupting their reproductive code (DNA) and inhibiting
them from reproducing. While there are varying opinions
about the effectiveness of UV light systems for pollutant
control, you should do additional research and consult
with HVAC professionals.
Controlling Dust
While preventing the build-up of dust may not
completely reduce asthmatic or allergic symptoms,
controlling dust is one of the most proactive measures
you can take in keeping the interior environment
healthy. The following steps can be taken to control the
amount of dust that accumulates in a house:
• Provide shoe storage at entrances for home owners
and visitors. Removing your shoes at the door
prevents tracking dust further into the home.
• Install a special HEPA filter in the air conditioner or
air purifier. This can help remove some allergens
such as pollen, animal dander, and tobacco smoke
from the air.
• Limit carpet, upholstered furniture, and heavy drapes
that collect dust. Upholstery and drapes should be
made from a tight-weave fabric that keeps out dust.
• Use hard-surfaced furniture that you can wipe clean.
• Avoid wall-to-wall carpeting. Use smaller rugs made of
cotton or wool that you can clean.
• Use roll-down shades or washable curtains.
• Damp-mop tile and hard surfaced floors rather than
sweeping. Use a washable cloth, instead of disposable
wipe.
• Design a central vacuum system into the plan, which
vents directly outdoors. If a central vacuum is not an
option, use a vacuum cleaner with a HEPA filter or a
special double-thickness bag, which collects dust-mite
particles and pollen.
• Consider wet-vacuum cleaning when possible.
This can help remove allergens from carpeting as it
washes the carpet. Consider periodic steam-cleaning
of carpets when possible. In addition to cleaning the
carpet, the heat of the steam kills dust mites.
510
GOING
GREEN
Improving Indoor Air Quality (Continued)
Mold Prevention
Exposure to mold can cause or worsen conditions
such as asthma, hay fever, or other allergies. The
most common symptoms of overexposure are cough,
congestion, runny nose, eye irritation, and aggravation
of asthma. Depending on the amount of exposure and
individual vulnerability, more serious health effects can
occur, such as fever and breathing problems.
Mold is most likely to grow where moisture is
trapped in improperly ventilated spaces such as
damp crawl spaces, misty bathrooms, and defective
wall systems. Because mold increases with humidity,
it is important to be aware of areas that can trap
humidity.
The key to preventing mold from forming is to
prevent weather from entering the building envelope
and by controlling the humidity inside the home. In
the design and construction of an energy-efficient
home, the exterior building envelope must be airtight
and watertight, and air movement must be controlled.
To ensure that all parts of the home remain dry, it
is important to include systems to supply proper
ventilation throughout the home. Examples of systems
used to help prevent water intrusion and mold growth
include: drainage planes behind exterior finishes,
properly sealed building envelopes, the use of moistureresistant building materials, heat recovery ventilation,
and ventilation fans in interior spaces.
Volatile Organic Compounds
Volatile organic compounds (VOC) are chemicals
contained in the items used in home construction,
which can emit pollutants throughout the life span of
the product. It is important to specify and use products
containing low or no VOCs. Products that should have
low or no VOCs include paint, caulks, sealants, cabinet
materials, plastics, and carpets. Reducing the amount of
VOCs present improves indoor air quality of the home,
and reduces exposure to toxic compounds.
A healthier alternative can be achieved with the
same color, texture, sheen, and quality of finish
using VOC-free paint. Look for the GreenSeal and ask
your paint supplier about the VOC content when
purchasing paint.
Polyvinyl chloride (PVC) is a widely used building
material found in products such as window frames,
flooring, and shower units. Despite appearing to be an
ideal building material, studies have shown that PVC has
high environmental and health costs. When designing
a home, consider alternatives such as wood-framed
windows, natural flooring materials, non-PVC plumbing
pipes, and tiled showers.
When buying or building cabinets, specify board
products that contain a urea-formaldehyde-free binder.
Urea-formaldehyde, found in many engineered wood
products, has been classified as a toxic air contaminant
by the California Air Resources Board, due to its potential
to cause cancer. Water-based wood finishes, such as
waterborne urethane or acrylic have decreased toxic
compounds, while still providing comparable durability.
Clean But Not So Green
Many home cleaning products emit synthetic chemicals,
such as VOC, and irritating fragrances. These substances
can have serious health issues for humans, pets, and the
environment. People absorb chemicals during use, and
the environment absorbs disposed products.
Americans spend 90% of their time indoors, so
cleaning with natural products is a huge step towards
making a healthy home. Commonly found harmful
substances in household cleaning products include the
following:
• Artificial fragrances can interfere with breathing
and cause skin irritation; some products contain
phthalates, which have been found to be carcinogenic
in lab experiments.
• Alkyphenol ethoxylates, used in detergents, have
been found to be a hormone disrupter.
• Butyl cellosolve, a common degreaser, can cause
nausea, headaches, and more serious issues when
inhaled.
• Petroleum, which is frequently found in conventional
cleansers and soaps, is flammable and releases
unwanted fumes.
Clean and Green Alternatives
Many companies make cleaning products containing
natural cleaning elements that can be purchased easily.
Look for products that use plant oils, grain alcohols,
and natural fragrances. When reading the label, you
should be able to recognize the ingredients. There are
also natural products you can use as cleaning agents,
including:
• Vinegar and water can be used to clean bathrooms
and windows.
• Baking soda can replace toxic abrasive chemicals to
clean toilets, tubs, and sinks.
• Citrus oils can replace artificial fragrances to freshen a
room without overpowering the air.
Toxin-free cleaning products are usually biodegradable
and do not pollute the air or water. Cleaning with natural
alternatives reduces your exposure to toxins and helps to
protect the environment.
GOING
GREEN
511
Improving Indoor Air Quality (Continued)
Radon
Radon is a cancer-causing, natural radioactive gas that
permeates from the ground. Radon is invisible to sight,
smell, and taste. Radon is the leading cause of lung
cancer among nonsmokers and is the second leading
cause of lung cancer in America. Because radon enters
from the ground, geological areas carry different levels
of contamination. Design and construction techniques
vary for different foundation types and site requirements.
Common elements to prevent radon build-up include a gas
permeable layer placed under the slab or flooring system
to allow the soil gas to move freely beneath the house.
In many cases, the material used is a 4" (100 mm) layer of
clean gravel. Plastic sheeting on top of the gas-permeable
layer prevents the soil gas from entering the home. A 3"
(75 mm) or 4" (100 mm) gas tight vent pipe runs from the
gas-permeable layer through the house and out through
the roof or exterior wall. This safely vents radon and other
soil gases above the house. An electrical junction box can
be installed in case an electric venting fan is needed later
to provide additional radon ventilation. Consult a radon
professional or the Environmental Protection Agency (EPA)
(www.epa.gov) for information on the radon risk levels in
your area and for appropriate control techniques.
Sealing Your Home from the Garage
Many home designs include an attached garage. An
attached garage keeps you dry as you get to and from
your car, and allows for ease of moving items from the
car into the house. An attached garage can allow for
a more compact building footprint in places where
HVAC DRAWINGS
Drawings for the HVAC system show the size and
location of all equipment, ductwork, and components with accurate symbols, specifications, notes, and
schedules that form the basis of contract requirements
for construction. Specifications are documents that
accompany the drawings and contain all pertinent
written information related to the HVAC system. The
HVAC drawings for a central forced-air system were
described at the beginning of this chapter. A simplified HVAC plan shows supply and return registers and
airflow values, while the detailed HVAC plan shows
the equipment, duct runs with size specifications,
and register locations with airflow values. Refer back
to Figure 21-3 and Figure 21-4 to see the simplified
space is at a premium. While an attached garage has
advantages, there are items inside the garage that
need to be isolated from the occupants. Chemicals,
paints, oils, and cleaning agents stored in the garage
can attribute to air quality concerns if they leak.
Automobiles emit dangerous carbon monoxide (CO)
gas when their engines are running. It is important
to prevent dangerous gases and toxins from entering
the home. An easy measure is to seal any gaps in walls
that the home shares with the garage. Install a carbon
monoxide monitor in any room adjacent to the garage,
and consider installing a fan attached to the garage
door opener to vent the garage when you leave with
the automobile.
Mechanical Systems and Your Garage. Mechanical
systems and ductwork placed in the garage can pull air
from the garage and push the air around in the house.
When possible, make sure to avoid the placement of
ductwork or mechanical equipment in the garage to
prevent toxins from entering the HVAC system. Placing
the mechanical system and related ductwork in an
insulated area other than the garage also saves energy,
because any loss from the system remains indoors.
Detached Garages. Designing a home with a detached
garage is the safest way to stop gas and chemicals from
entering the home. Many factors need to be considered
when designing a home with a detached garage, such
as architectural style, personal preference, and available
space on the building site.
and detailed HVAC plans for the model house used
throughout this textbook.
HVAC drawings may or may not be necessary for
residential buildings, depending on the requirements
of the local building department or the lending agency.
Drawings can be prepared by the architect, architectural
designer, or the architectural drafter, but these drawings
are generally created by the heating contractor when a
complete HVAC layout is necessary.
For commercial buildings, the HVAC plan can be
prepared by an HVAC engineer as a consultant for the
architect. The engineer who designs HVAC systems is
also referred to as a mechanical engineer. The consulting engineer is responsible for the HVAC design and
installation. The engineer determines the placement
of all equipment and the location of all duct runs and
512
Architectural Drafting and Design
FIGURE 2117 Single-line HVAC plan engineer’s sketch.
components. The consulting engineer also determines
the specifications for heating, cooling, and other unit
and duct sizes, based on calculations of building
volume, exterior surface areas and construction materials, rate of airflow, and pressure. The consulting
engineer can prepare single-line sketches or submit
data and calculations to a design drafter, who prepares
design sketches or final drawings. Drafters without
design experience work from engineering or design
sketches to prepare formal drawings. A single-line engineer’s sketch is shown in Figure 21-17. The next step in
the HVAC design is for the drafter to convert the rough
sketch into a preliminary drawing. This preliminary
drawing goes back to the engineer and architect for
5"Ø
DISPATCH
103
COND.
E-1
UNIT
750 CFM
#3
C-1
370 CFM
TRANSITION TO 18 x 8 &
RUN BETWEEN JOISTS
OVER DISPATCH 103.
2. Label duct sizes within the duct when space is avail-
able. Place the note next to the duct when space is
not available inside the duct, or use a note with a
leader to the duct in other situations.
E-8
50 CFM
C-22
60 CFM
12 x 12
LOBBY
102
ACU-1
V.D.
CORRIDOR
135
10 x 10
E-3
240 CFM
12"Ø
C-2
600 CFM
C-3
140 CFM
MUNICIPAL COURT
125
1
M-3
FLOOR PLAN – MECHANICAL
SCALE: 1/4" = 1"-Ø"
GENERAL NOTES:
1
VERIFY ALL EXISTING CONDITIONS AT SITE.
2
SEE ARCHITECTURAL FLOOR PLAN FOR 1-HR
RATED AREAS. PROVIDE FIRE DAMPERS AS
SCHEDULED AND AS REQ'D BY CODE.
ACU-2
14 x 12
8x8
V.D.
VESTIBULE
101
UP TO 18 x 18 FIBERGLASS
O.S.A. VENT ON ROOF
UP TO 24 x 24 FIBERGLASS
O.S.A. VENT ON ROOF
E-2
250 CFM
12"Ø
12 x 12
12 x 12
12 x 8
1. Draw duct runs using 0.5 mm line widths.
5"Ø
16 x 11
C-10
45 CFM
TELECOMM
104
verification and corrections or changes. The final step
in the design process is for the drafter to implement the
design changes on the preliminary drawing to establish
the final HVAC drawing. The final HVAC drawing is
shown in Figure 21-18.
When the drafter converts an engineering sketch to
a formal drawing, the easiest-to-read format should be
used. For example:
FIGURE 2118 HVAC plan created from the engineer’s sketch shown in Figure 21-17.
8"Ø
C-4
260 CFM
SARGEANT
124
14 x 12
12 x 10
1O x 8
12 x 10
E-3
240 CFM
C-4
260 CFM
LIEUTENANT
123
V.D.
8"Ø V.D.
Chapter 21: Heating, Ventilating, and Air-Conditioning
513
FORMAL HVAC PLAN DRAWINGS
ENGINEERING
E-1
800 CFM
16 24
C-1
240 CFM
14 12
S-1
450 CFM
16 12
16 12
20 12
10 10
8"Ø
C-2
300 CFM
12 12
UP TO 24 24
FIBERGLASS
VENT ON ROOF
16 16
ACU-1
FIGURE 2119 Examples showing engineering sketches converted to formal HVAC plan drawings.
3. Note duct sizes as 22 × 12 (550 × 300 mm) or 22/12,
where the first number, 22, is the duct width and the
second number, 12, is the duct depth.
4. Place notes on the drawing to avoid crowding.
Aligned dimensioning can be used, where horizontal
notes read from the bottom of the sheet and vertical notes read from the right side of the sheet. Make
notes clear and concise.
5. Refer to schedules to get specific drawing information that is not available on the sketch. Schedule
information is found in the following discussion.
6. Label equipment with a note next to the equipment
symbol or with a note and leader pointing to the
equipment symbol.
Figure 21-19 shows several examples of duct system
components, comparing the engineering sketch and the
formal drawing.
Single- and Double-Line HVAC Plans
HVAC plans are drawn over the floor plan as a layer.
The floor plan layout is drawn first as a base sheet for
the HVAC layout and other layers. The HVAC plan is
then drawn or plotted using 0.5 mm lines for contrast
with the floor plan and notes are used to label the
components as previously described. The HVAC plan
shows the placement of equipment and ductwork. Duct
size is given in inches or millimeters, and duct shape
514
with symbols, where Ø is the symbol for a round duct,
and is the symbol for a square or rectangular duct.
Other ductwork and system components are placed on
the drawing or keyed to schedules. Drawings can be
either single- or double-line, depending on the needs of
the client or how much detail must be shown. Singleline drawings are easier and faster to draw. In many
situations they are adequate to provide the equipment
placement and duct routing, as shown in Figure 21-20.
Double-line drawings take up more space and are more
time-consuming than single-line, but they are often
necessary when complex systems require more detail,
as shown in Figure 21-18.
Architectural Drafting and Design
Detail Drawings
Detail drawings are used to clarify specific features of
the HVAC plan. Single- and double-line drawings are
intended to establish the general arrangement of the
system, but they do not always provide enough information to fabricate specific components. When further
clarification of features is required, detail drawings
are made. Detail drawings are enlarged views of equipment, equipment installations, duct components, or
any features that are not defined on the plan. Detail
drawings can be scaled or unscaled. Detail drawings
provide adequate views and dimensions for sheet
metal shops to prepare fabrication patterns, as shown
in Figure 21-21. Scaled details are drawn at 1/2" = 1'–0"
to 1 1/2" = 1'–0".
Section Drawings
Sections, also referred to as section drawings or sectional views, are used to show and describe the interior
portions of an object or building that would otherwise
be difficult to visualize. Section drawings provide a
clear representation of construction details or a profile
of the HVAC plan as taken through one or more locations in the building. Two basic types of section drawings are used in HVAC. One method is used to show
the construction of the HVAC system in relationship
to the building. In this case the building is sectioned,
and the duct system is shown unsectioned. This drawing provides a profile of the HVAC system. There can
be one or more sections taken through the building,
ACOUSTICALLY LINED BOX
OVER CEILING OUTLET 14"
HIGH @ NECK OPENING.
RIGID FIBERGLASS
SIZE AS NOTED.
3'-Ø" MAXIMUM
FLEX DUCT.
OPPOSED
BLADE
DAMPER
LAY-IN
T-BAR
CEILING
PERFORATED
OUTLET
CEILING OUTLET DETAIL
NO SCALE
FIGURE 2120 Single-line ducted system showing a layout
of the proposed trunk and run-out ductwork. Courtesy Trane
Company, La Crosse, Wisconsin.
GYPBOARD
CEILING
A
M-3
FIGURE 2121 Sample detail drawing. Courtesy W. Alan Gold,
consulting mechanical engineer and Robert Evenson Associates,
AIA Architects.
Chapter 21: Heating, Ventilating, and Air-Conditioning
515
14X10 RET AIR
12×12 SUPPLY
10X10
5"Ø
6"Ø
8X10
9"Ø
6"Ø
12X10
12X14
12"Ø RET AIR
ACU-1
12X12 RET AIR
6X10
10X12
16X14 FROM ACU-4
FIGURE 2122 Section drawing. Courtesy W. Alan Gold, consulting mechanical engineer and Robert Evenson Associates, AIA Architects.
depending on the complexity of the project. The building structure can be drawn using thin lines, as shown
in Figure 21-22. Figure 21-22 shows a section through
the HVAC plan first shown in Figure 21-18. The other
sectioning method is used to show detail of equipment
or to show how parts of an assembly fit together (see
Figure 21-23).
HVAC Schedules
Numbered symbols that are used on the HVAC plan
to key specific items to charts are known as schedules.
Schedules were discussed in detail in Chapter 16.
ROOF MOUNTED
HEAT PUMP
INSTALLED AND
FURNISHED BY
THE SOUTHLAND
CORP.
NOTE
4
NOTE
STILES MOUNTING
CURB INSTALLED
& LEVELED BY
GENERAL
CONTRACTOR
7
HP
1
ROOF
NOTE
3
18"o FLEX DUCT
1Ø"o DUCT5 TO WORK RM.
& LOCKED STORAGE
PLENUM FURNISHED
& INSTALLED BY THE
SOUTHLAND CORP.
NOTE
6
SECTION
A
CEILING
FIGURE 2123 Detailed section showing HVAC equipment
installation. Courtesy The Southland Corporation.
Schedules describe items such as ceiling outlets, supply
and exhaust grills, hardware, and equipment. Schedules
are charts of materials or products that include size,
description, quantity used, capacity, location, vendor
specifications, and any other information needed to
construct or finish the system. Schedules keep the drawing clear of unnecessary notes. Schedules are generally
placed in any convenient area of the drawing field or on
a separate sheet.
Items on the plan can be keyed to schedules by
using a letter and number combination, such as C-1
for CEILING OUTLET NO. 1, E-1 for EXHAUST
GRILL NO. 1, or ACU-1 for EQUIPMENT UNIT
NO. 1. The exhaust grill schedule keyed to the HVAC
plan in Figure 21–18 is set up as a table as shown in
Figure 21-24.
HVAC Pictorial Drawings
Pictorial drawings can be isometric or oblique as shown
in Figure 21–25. An isometric drawing is a pictorial
drawing where length, width, and height are represented by lines 120° apart, with all measurements in
the same scale. An oblique drawing has the object
shown with one surface parallel to the viewing plane,
and depth is represented by lines drawn, typically, at a
45° angle. Pictorial drawings are usually not drawn to
scale. They are used in HVAC for a number of applications, such as visualization of the duct system and
when the plan and sectional views are not adequate to
show difficult duct routing.
516
Architectural Drafting and Design
EX HAUS T G RI L L S C H EDU L E
DA MP E R T Y P E
SYMBOL
E
E
E
E
E
E
E
E
E
E
E
E
E
–
–
–
–
–
–
–
–
–
–
–
–
–
1
2
3
4
5
6
7
8
9
10
11
12
13
SIZE
CFM
24x12
18x18
1Øx1Ø
1Øx1Ø
12x12
1Øx1Ø
6x6
12x6
12x6
12x8
1Øx1Ø
9x4
9x4
75Ø
72Ø
24Ø
35Ø
28Ø
5ØØ
35Ø
5Ø
2ØØ
15Ø
29Ø
16Ø
75
LOCATION
FIRE
DPR.
REMARKS
KEY OP. KEY OP.
OPPBLD EXTR
NO
DPR.
TYPE
4
2
1
1
1
1
2
3
3
3
3
1
4
HIGH WALL
CEILING
CEILING
CEILING
CEILING
CEILING
HIGH WALL
24x24 PANEL
24x24 PANEL
TYPE 1: KRUGER 119Ø SERIES STEEL PERFORATED FRAME 23
FOR LAY-IN TILE.
TYPE 3: KRUGER EGC-5: 1/2"x1/2"x1/2" ALUMINUM GRID.
TYPE 2: KRUGER 119Ø SERIES STEEL PERFORATED FRAME 22
FOR SURFACE MOUNT.
TYPE 1: KRUGER S8ØH: 35° HORIZ. BLADES 3/4" O.C.
FIGURE 2124 Exhaust grill schedule.
STEAM SUPPLY AND
RETURN
CIRCULATING
PUMP
WATER SUPPLY AND
RETURN TO OTHER UNITS
WATER
CHILLER
WATER
COOLING
COIL
OUTSIDE
AIR
CT
IR
YA
DU
L
PP
SU
FILTER
PREHEAT
RETURN AIR
FIGURE 2125 Pictorial drawings. Courtesy Trane Company, La Crosse, Wisconsin.
HVAC PLAN DRAWING
CHECKLIST
❑ Provide steel post embedded in concrete in front of
furnace located in garage.
Check off the items in the following list as
you work on the HVAC plan, to be sure that you have
included all the necessary items:
Simplified plan:
❑ Furnace shown with make and model, Btu output,
and electrical requirements.
Minimum requirements:
❑ Furnace shown with make and model, Btu output,
and electrical requirements.
❑ Provide steel post embedded in concrete in front of
furnace located in garage.
❑ Warm air (WA) registers and sizes.
Chapter 21: Heating, Ventilating, and Air-Conditioning
❑ Cubic feet per minute (cfm) at each register.
❑ Return air (RA) and size specification.
Detailed plan:
❑ Furnace shown with make and model, Btu output,
and electrical requirements.
❑ Provide steel post embedded in concrete in front of
furnace located in garage.
❑ Supply ducts and sizes.
❑ Warm-air (WA) registers and sizes.
517
❑
❑
❑
❑
Cubic feet per minute (cfm) at each register.
Return ducts and sizes.
Return air and size specification.
Btu heat loss for each room.
Additional items for a commercial plan:
❑ Schedules keyed to plan.
❑ Detail drawings if needed.
❑ One or more section drawings.
❑ Detailed section or sections if needed.
CADD APPLICATIONS
CADD in the HVAC Industry
INTRODUCTION
In some HVAC CADD software, you place the duct
fittings and then the software automatically sizes ducts
in accordance with common mechanical equipment
manufacturer specifications. The floor plan is commonly
used as a background layer, and the HVAC plan is a
separate layer. The following is a sample of the steps that
can be used by the CADD drafter to design and draw an
HVAC plan:
FD
STEP 1 For the preliminary layout, draw the duct center lines,
as shown in Figure 21-26.
STEP 2 Select supply and return registers from a symbol
library, and add the symbol to the end of the center lines
where appropriate, as shown in Figure 21-27.
STEP 3 The CADD program then automatically identifies
and records the lengths of individual duct runs, and tags
each run. Fittings are located and identified by the type
FIGURE 2127 Automatically placing supply and return
registers.
of intersection, as shown in Figure 21-28. While all of this
drawing information is added to the layout, the computer
automatically gathers design information into a file for
duct sizing based on specific mechanical manufacturer
specifications that you select.
STEP 4 After the fitting location and sizes are deter-
FIGURE 2126 Preliminary layout of duct center lines.
mined, the program transforms each fitting into accurate double-line symbols exactly to the ANSI Y32.2.4
standard as shown in Figure 21-29. ANSI stands for the
American National Standards Institute. ANSI Y32.2.4 is
titled Graphic Symbols for Heating, Ventilating and Air
Conditioning. This standard has been developed for use
on HVAC drawings as a common application throughout the industry.
518
Architectural Drafting and Design
CADD APPLICATIONS
CADD in the HVAC Industry (Continued)
40
50
10
50
40
40
30
111
40
150
143
50
127
50
114
110
10
111
50
111
50
107 30
81
165
30
124
118
24
24
FD
FD
20
110
30
30
116
20
162
10
116
100
30
30
100
30
68
131
40
38
40
10
50
50
40
30
24
FD
20
20
10
30
30
20
128
128
FIGURE 2130 Complete HVAC CADD layout.
FIGURE 2128 Fittings located and identified.
50
40
10
40
40
14
97
20
10
128
41
115
20
116
44
141
20
30
20
111
62
20
20
10
51
118
30
20
40
10
The increase in productivity is excellent with CADD.
Also, the CADD program can automatically record
information while you draw, generating a complete
bill of materials. The systems that offer the greatest
flexibility and productivity are designed as a parametric
package. This program type allows you to set the design
parameters that you want to use. Then the computer
automatically draws and details according to these
settings. As you draw, information is placed with each
fitting, including type of fitting, cfm airflow, and material
thickness.
40
HVAC PICTORIALS
FIGURE 2129 Fitting symbols automatically drawn.
STEP 5 When the fittings are in place, the program calculates
and draws the connecting ducts and adds couplings automatically at the maximum duct lengths. If a transition
fitting is needed in a duct run, the program recommends
the location. All you have to do is pick a transition fitting
from the symbol library. A transition fitting is a standard
or custom duct component that connects one duct size to
a different duct size, or one duct shape to a different duct
shape, or both different shape and size. See Figure 21-30
for the complete HVAC layout.
CADD applications can make pictorial representations
much easier to create, especially when the HVAC
program allows direct conversion from the plan view
to the pictorial. CADD pictorials, known as graphic
models, are used to view the HVAC system from any
angle or orientation. Custom HVAC CADD programs
automatically analyze the layout for obstacles where
an error in design can result in a duct that does
not have a clear path. When changes are made
to an HVAC plan, plans created in CADD offer a
distinct advantage: Any changes on one drawing
are corrected on all drawings, schedules, and lists
of materials. Figure 21-31 shows a CADD-generated
perspective of HVAC duct routing.
Chapter 21: Heating, Ventilating, and Air-Conditioning
519
CADD APPLICATIONS
FIGURE 2131 CADD-generated perspective of HVAC duct routing. Courtesy Computervision Corporation.
CADD LAYERS FOR HVAC DRAWINGS
The American Institute of Architects (AIA) CAD Layer
Guidelines establish the heading “Mechanical” as the
major group identification for HVAC-related CADD layers.
The following are some of the recommended CADD layer
names for HVAC applications: ■
Layer Name
Description
M-CHIM
Prefabricated chimneys
M-CMPA
Compressed air systems
M-CONT
Controls and instrumentation
M-CWTR
Chilled water system
M-DETL
Details
M-DUST
Dust- and fume-collection systems
M-ELEV
Elevations
M-EMER
Emergency management systems
M-EXHS
Exhaust systems
M-FUEL
Fuel system piping
M-HOTW
Hot water heating system
M-HVAC
HVAC system
M-REFG
Refrigeration systems
M-SCHD
Schedules and title block sheets
M-SECT
Sections
M-STEM
Steam systems
520
Architectural Drafting and Design
ADDITIONAL RESOURCES
See CD for more information
The following Web sites can be used as a resource to
help you research available products and HVAC design
options.
These Web site links are also provided on the Student
CD where you can select a link and go automatically to
the specified Web site.
Address
www.ashrae.org
Company, Product,
or Service
American Society of
Heating, Refrigerating,
www.carrier.com
www.lennox.com
www.trane.com
and Air-Conditioning
Engineers, Inc.
HVAC equipment
manufacturer
HVAC equipment
manufacturer
HVAC equipment
manufacturer
Heating, Ventilating, and Air-Conditioning Test
See CD
for more
information
QUESTIONS
DIRECTIONS: Answer the following questions with short, complete statements or drawings as needed on an 8 1/2" × 11" sheet
of notebook paper, or complete the electronic chapter test on
the Student CD.
1. Letter your name, Chapter 21 Test, and the date at the top of
the sheet.
2. Letter the question number and provide the answer. You do
not need to write the question. Answers can be prepared on
a word processor if approved by your course guidelines.
Question 21–1 Describe the following heating and
cooling systems:
Question 21–8 List five advantages of a central vacuum
system.
Question 21–9 What does the size of heating and
cooling equipment have to do with providing access
clearances for servicing and replacement?
Question 21–10 Define combustion air.
Question 21–11 List the rooms or locations where
return air cannot be accessed.
Question 21–12 What does the abbreviation UL stand for?
a. Central forced air
Question 21–13 Give the minimum thermal resistance
value for insulated ducts.
b. Hot water
Question 21–14 Define plenum.
c. Heat pump
Question 21–15 Describe the purpose of schedules in an
HVAC drawing.
d. Zoned heating
Question 21–2 Describe a type of zoned heating called
radiant heat.
Question 21–3 List two advantages and two disadvantages of zonal heat as compared with central forcedair heating.
Question 21–4 A heat pump may supply up to how
many times as much heat per year for the same
amount of electrical consumption as a standard
electric forced-air system?
Question 21–5 Discuss four factors that influence the
placement of a thermostat.
Question 21–6 Describe five sources that can contribute
to an unhealthy living environment.
Question 21–7 Discuss the function of an air-to-air heat
exchanger.
PROBLEMS
Problem 21–1 Calculate the minimum heat exchanger
capacity for one of the floor plans found in the floor
plan problems at the end of Chapter 18. Use the
formulas established earlier in the “Air-to-Air Heat
Exchangers” section of this chapter.
Problem 21–2 Using the residential heating engineering
sketch of the main floor plan and basement provided
with this problem, do the following:
1. Draw a formal double-line HVAC floor plan layout
at a scale of 1/4" = 1'–0".
2. Approximate the location of undimensioned fea-
tures such as windows.
3. Use line thicknesses as described in this chapter.
Chapter 21: Heating, Ventilating, and Air-Conditioning
521
5'-6"
9'-Ø"
5'x4'
5'x6'-8"
4x12
5482 BTU
154 CFM
2x1Ø
6
1325 BTU
37 CFM
7
23'-Ø"
VENT OUT
F
545 BTU
15 CFM
HOOD FAN VENT OUT
R
6
12'-Ø"
3459 BTU
97 CFM
4'x3'-6"
4x1Ø
4'x4'
13'-Ø"
3'-Ø"
8x24
9
7
11'-Ø"
26'-Ø"
2x1Ø
7
4324 BTU
4x12 121 CFM
6
2740 BTU
77 CFM
2083 BTU
58 CFM
4x1Ø
4'x4'
11'-Ø"
2'-6"
3655 BTU
102 CFM
4x12
7
6
6x5
4x1Ø
4'x4'
1Ø'-6"
7'-Ø"
24'-Ø"
11'-Ø"
18'-Ø"
TOTAL HEAT LOSS 23,885 BTU
675 CFM
42'-Ø"
26'- Ø"
16/14
FURNACE
1Ø'-Ø"
22 x 30
CRAWL
ACCESS
14/12
8"
6"
HOUSE ABOVE
U P
24'-Ø"
GARAGE
7'- Ø"
9'- Ø"
12"
BASEMENT FURNACE HEATING PLAN
Problem 21–3 Using the residential air-to-air heat
exchanger ducting engineering sketch of a basement
floor plan provided with this problem, do the following:
1. Draw a formal single-line air-to-air heat exchanger
floor plan layout at a scale of 1/4" = 1'–0".
2. Approximate the location of undimensioned fea-
tures such as doors.
3. Use line thicknesses as described in this
chapter.
522
Architectural Drafting and Design
Problem 21–4 Using the plan that you have been
drawing from Chapter 18, design and draw your own
simplified HVAC plan.
5. Ceiling height: 8'–0"
Problem 21–5 Using the plan that you have been
drawing from Chapter 18, design and draw your own
double-line HVAC plan.
7. Frame wall insulation: R-19 + 1/2" polystyrene
Problem 21–6 Using the plan that you have been
drawing from Chapter 18, design and draw your own
double-line air-to-air heat exchanger plan.
Problem 21–7 Prepare heat loss and gain calculations
for the plan that you have been drawing from
Chapter 18, unless otherwise specified by your
instructor. Use the residential heating data sheets
and the residential cooling data sheets found on the
Student CD. Complete the data sheets according
to the method used in this chapter to solve for the
total winter heat loss and summer heat gain. Use the
following criteria unless otherwise specified by your
instructor:
1. Outdoor temperature: As recommended for your
area. You need to do some research to determine this
value.
2. Indoor temperature: 70°F (21°C)
3. Double-glass windows and glass doors
4. Urethane insulated metal exterior doors, weather-
stripped
6. Ceiling insulation: Confirm with your local building
department.
8. Floor insulation over unconditioned space: Confirm
with your local building department.
9. Duct insulation requirements: Confirm with your
local building department or a professional HVAC
contractor.
10. Masonry above and below grade: As required in
your selected plan.
11. Basement floor or concrete slab construction: As
required for your selected plan. Verify use with your
instructor.
12. Assume that the entry foyer door faces south to
establish window orientation.
13. Assume glass with an inside shade.
14. Number of occupants (optional): Select the family
size you desire or count the bedrooms and add one.
For example, a three-bedroom home plus one equals
four people.
15. Latent load conditions: Use typical for your local
area. Select wet, medium, medium dry, or dry as
appropriate. You need to do some research to determine these values, or consult with your instructor.
Chapter 21: Heating, Ventilating, and Air-Conditioning
523
Problem 21–8 Given the following:
measured the given engineer’s sketch at 1/16" = 1'–0"
(1:200 metric). Now you convert the established
dimensions to a formal drawing at 1/4" = 1'–0"
(1:50 metric). Approximate the location of the
HVAC duct runs and equipment in proportion to
the presentation on the sketch.
1. HVAC floor plan engineering layout at approximately
1/16" = 1'–0" (1:200 metric). The engineer’s layout
is rough, so round off dimensions to the nearest
convenient units. For example, if the dimension you
scale reads 24'–3" (7391 mm), round off to 24'–0"
(7300 mm). The floor plan does not require dimensioning; therefore, the representation is more important than the specific dimensions.
2. Prepare correlated schedules in the space available.
Set up the schedules in a manner similar to the
examples below.
2. Related schedules.
3. Make a detail drawing of the exhaust hood, either
scaled or unscaled. Make the detail large enough to
clearly show the features.
3. Engineer’s sketch for exhaust hood.
Do the following:
1. Make a formal double-line HVAC floor plan layout
at a scale of 1/4" = 1'–0" (1:50 metric). Note: You
o 1Ø"
TANGENT
36"
8"
36"
(o 1Ø")
8"
24"
1Ø"
EXHAUST HOOD DETAIL
18/12 RETURN DUCT DOWN IN CORNER
22 x 12 C-10
230 CFM
16 x 12
S-1
450 CFM
C-12
40 CFM
2'-6"
36 x 36 EXHAUST HOOD
OVER SOLVENT TANK
SEE DETAIL
12 x 12
C-14
300 CFM
INTERIOR WALLS
5" THK
20 x 12
o 1Ø"
C-13
45 CFM
2'-6"
3'-Ø"
18 x 12
E-5
1000 CFM
3'-Ø"
FROM EXIST SYSTEM
4'-Ø"
8x6
C-11
185 CFM
o 1Ø" EXHAUST DUCT
UP TO REF-1
S-2
450 CFM
1Ø x 8
IN JOIST SPACE
PROPOSED ADDITION HVAC PLAN
o 9"
8 x 1Ø
DH
EXT WALLS
8" THK
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