EGEE 102 – Energy Conservation
And Environmental Protection
Home Heating Basics
National Average Home
Energy Costs
14%
Heating and Cooling
44%
Refrigrator
Lighting, Cooking and
other Appliances
Water Heating
33%
9%
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Why do we need
Heating?
30 F
70 'F
Furnace
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Typical Heat lossesConventional House
5% through ceilings
17% through
frame walls
1% through
basement floor
16%
through
windows
3% through door
38% through cracks
in walls, windows,
20%
through and doors
basement
walls
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Heat Transfer
• Conduction
• Convection
• Radiation
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Conduction
Energy is conducted down
the rod as the vibrations of
one molecule are passed
to the next, but there
is no movement of energetic
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Convection
Energy is carried by the
bulk motion of the fluid
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Radiation
Energy is carried by
electromagnetic waves.
No medium is required
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Degree Days
• Index of fuel consumption indicating how
many degrees the mean temperature fell
below 65 degrees for the day
• Heating degree days (HDD) are used to
estimate the amount of energy required
for residential space heating during the
cool season.
• Cooling degree days (CDD) are used to
estimate the amount of air conditioning
usage during the warm season
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How do we calculate
HDD?
• HDD = Tbase - Ta
• if Ta is less than Tbase
• HDD = 0
• if Ta is greater or equal to Tbase
• Where: Tbase = temperature base, usually
65 F Ta = average temperature, Ta =
(Tmax + Tmin) / 2
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Heating Degree Days
• Calculate the number of degree
days accumulated in one day in
which the average outside
temperature is 17ºF.
Degree days = 1 day ( 65 – Tout)
= 1 (65-17)
= 48 degree days
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Heating Degree Days in
a Heating Season
• Calculate the degree days
accumulated during a 150-day
heating season if the average
outside temperature is 17ºF
Solution:
Heating Season Degree days
= 150 days ( 65 – Tout)
= 150 (65-17)
= 7,200 degree days
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Degree Days for the
Heating Season
PLACE
Birmingham,
ALABAMA
Anchorage,
ALASKA
Barrow, ALASKA
Tucson, ARIZONA
Miami, FLORIDA
State College
DEGREE DAYS
2,780
10,780
19,994
1,776
173
???
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Class work
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Significance of HDD
• Mrs. Young is moving from Anchorage, Alaska
(HDD =10,780) to State college, PA (HDD =
6,000). Assuming the cost of energy per
million Btu is the same at both places, by what
percentage her heating costs will change?
Solution
HDD in Anchorage, Alaska = 10,780
HDD in State College PA = 6,000
Difference = 10,780 - 6,000 = 4,780
Saving in fuel costs are  4,780 100  44.3%
10,780
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Home Energy Saver
• http://homeenergysaver.lbl.gov/
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Home Heating Costs in
State College
Average House
$232 $106
$890
$305
$227 $133
$52
Heating
Cooling
Hot water
Appliances
Misc.
Lighting
Energy Efficient
House
Energy Effcient House
$327
$232
Total $1,891
$205
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$114
$89
Total 18
$1,019
Home Heating Costs
• Related to amount of insulation,
material that resists the flow of heat
• Insulation is rated in terms of
thermal resistance, called R-value,
which indicates the resistance to
heat flow. The higher the R-value,
the greater the insulating
effectiveness. The R-value of
thermal insulation depends on the
type of material, its thickness, and
density.
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• R-30 better than
R-11
Places to Insulate
• Attic is usually the
easiest ad most
cost effective
place to add
insulation
• Floors above
unheated
basements should
be insulated
• Heated basements
should be
insulated around EGEE 102
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R-values for Building
Materials
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Thickness of various
materials for R-22
110"
18"
6"
Cellulose
Fiber
7"
Fiberglass
Pine wood
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Common
brick
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R-Value for a Composite
Wall
R-Value of material
1/2" Plasterboard
0.45
3 1/2" Fiberglass
10.90
3/4" Plywood
0.94
1/2" Wood siding
0.81
RTOTAL = 13.10
ft2 – °F – hr
BTU
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Home Heating Energy
• Heat loss depends
on
• Surface Area
(size)
• Temperature
Difference
• Property of the
wall ( R value)
Q (Btus)
t (time, h)
=
1
R
Inside
65¨F
Outside
30¨F
A (area) x Temperature Diff (Ti – To)
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Heat Loss
Thot
Tcold
Q
t
Heat Loss =
Q
t
AreaxTinside  Toutside 
 , R)
AreaxTRe
 Tce oftheWall
(Thermal
sis tan
inside
outside
(Thermal Re sis tan ce oftheWall , R)
Id Q/t is in Btu/h
Area in ft2
Tin-Tout in °F
Then the thermal resistance is
R-value. The units of R-value are
ft 2 x oF
Btu / hr
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Wall loss rate in BTUs
per hour
• For a 10 ft by 10 ft room with an 8 ft
ceiling, with all surfaces insulated to R19
as recommended by the U.S. Department
of Energy, with inside temperature 68°F
and outside temperature 28°F:



Q 320 ft 2 x 68 F  280 F
Heatloss Rate  
 674 Btu / hr
2 0
ft x F
t
19
BTU / h
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Calculation per Day
• Heat loss per day = (674 BTU/hr)(24
hr) = 16,168 BTU
• Note that this is just through the wall
• The loss through the floor and
ceiling is a separate calculation, and
usually involves different R-values
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Calculate loss per
"degree day"
•This is the loss per day with a one degree
difference between inside and
outside temperature.
• If the conditions of case II prevailed all day, you
would require 40 degree-days of heating, and
therefore require 40 degree-days x 404
BTU/degree day = 16168 BTU to keep the inside
temperature constant.
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Heat Loss for Entire
Heating Season.
• The typical heating requirement for
a Pittsburgh heating season,
September to May, is 5960 degreedays (a long-term average).
Heat loss = Q/t = 404 Btu/degree day x 5960 degree days
= 2.4 MM Btus
The typical number of degree-days of heating
or cooling for a given geographical location
can usually be obtained from the weather service.
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Numerical Example
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Heat loss Calculation
1

Qtotal     A   Number of Annual deg ree days  24 h / day 
R

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Problem
• A wall is made up of four elements, as
follows
• ½” wood siding
• ½” plywood sheathing
• 3 ½ in of fibber glass
• ½” of sheet rock
• How many Btus per hour per sq.ft. will be
lost through the wall when the outside
temperature is 50F colder than inside?
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Economics of Adding
Insulation
• Years to Payback =
C(i) x R(1) x R(2) x E
------------------------------------C(e) x [R(2) - R(1)] x HDD x 24
•
•
•
•
•
•
•
•
C(i) = Cost of insulation in $/square feet
C(e) = Cost of energy, expressed in $/Btu
E = Efficiency of the heating system
R(1) = Initial R-value of section
R(2) = Final R-value of section
R(2) - R(1) = R-value of additional insulation being considered
HDD = Heating degree days/year
24 = Multiplier used to convert heating degree days to heating hours (24
hours/day).
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Pay Back Period
Calculation
• Suppose that you want to know how many years
it will take to recover the cost of installing
additional insulation in your attic. You are
planning to increase the level of insulation from
R-19 (6 inch fiberglass batts with moisture
barrier on the warm side) to R-30 by adding R-11
(3.5 inch unfaced fiberglass batts). You have a
gas furnace with an AFUE of 0.88. You also pay
$0.70/therm for natural gas.
• Given
• C(i) = $0.18/square foot; C(e) = ($0.70/therm)/(100,000
Btu/therm) = $0.000007/Btu; E = 0.88; R(1) = 19; R(2) = 30;
R(2) - R(1) = 11; HDD = 7000
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Household Heating Fuel
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
56%
Heating Fuel
26.00%
11.00%
Natural
Gas
Electricity Fuel Oil
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10.00%
Other
35
Average Heating Value
of Common Fuels
Fuel Type
Kerosene (No. 1 Fuel Oil)
No. 2 Fuel Oil
Electricity
Natural Gas
Propane
Bituminous Coal
Anthracite Coal
Hardwood (20% moisture)*
Pine (20% moisture)*
Pellets (for pellet stoves; premium)
No. of Btu/Unit (Kilocalories/Unit)
135,000/gallon (8,988/liter)
140,000/gallon (9,320/liter)
3,412/kWh (859/kWh)
1,028,000/thousand cubic feet (7,336/cubic meter)
91,333/gallon (6,081/liter)
23,000,000/ton (6,400,000/tonne)
24,800,000/ton (5,670,000/tonne)
24,000,000/cord (1,687,500/cubic meter)
18,000,000/cord (1,265,625/cubic meter)
16,500,000/ton (4,584,200/tonne)
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Typical Heating Furnace
Efficiencies
Fuel Type - Heating Equipment
Coal (bituminous)
Central heating, hand-fired
Central heating, stoker-fired
Water heating, pot stove (50 gal.[227.3 liter])
Oil
High efficiency central heating
Typical central heating
Water heater (50 gal.[2227.3 liter])
Gas
High efficiency central heating
Typical central heating
Room heater, unvented
Room heater, vented
Water heater (50 gal.[227.3 liter])
Electricity
Central heating, resistance
Central heating, heat pump
Ground source heat pump
Water heaters (50 gal.[227.3 liter])
Wood & Pellets
Franklin stoves
Stoves with circulating fans
Catalytic stoves
Pellet stoves
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Efficiency (% )
45
60
14.5
89
78
59.5
92
82
91
78
62
97
200+
300+
97
102
30.0 - 40.0
40.0 - 70.0
65.0 - 75.0
85.0 - 95.0
37
Comparing the Fuel
Costs
Energy Cost 
Cost perUnit ofFuel
HeatingValue( MMBtu / unitoffuel)  Efficiency
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Fuel Costs
• Electric resistance heat cost =
$0.082 (price per kWh) / [ 0.003413 x 0.97
(efficiency)] = $24.77 per million Btu.
• Natural gas (in central heating system) cost =
$6.60 (per thousand cubic feet) / [ 1.0 x 0.80
(efficiency)] = $8.25 per million Btu.
• Oil (in central heating system) cost =
$0.88 (price per gallon) / [ 0.14 x 0.80
(efficiency)] = $7.86 per million Btu.
• Propane (in central heating system) cost =
$0.778 (price per gallon) / [ 0.0913 x 0.80
(efficiency)] = $10.65 per million Btu.
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Heating Systems
•
•
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Heating Systems
• Some hot water
systems circulate
water through
plastic tubing in
the floor, called
radiant floor
heating.
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Electric Heating
Systems
1. Resistance heating systems
Converts electric current directly into
heat
1. usually the most expensive
2. Inefficient way to heat a building
2. Heat pumps
Use electricity to move heat rather than to
generate it, they can deliver more
energy to a home than they consume
1. Most heat pumps have a COP of 1.5 to 3.5.
2. All air-source heat pumps (those that
exchange heat with outdoor air, as opposed
to bodies of water or the ground) are rated
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with a "heating
season
performance factor"42
Geothermal Heat Pumps
• They use the Earth
as a heat sink in
the summer and a
heat source in the
winter, and
therefore rely on
the relative
warmth of the
earth for their
Additional reading
heating and
http://www.eren.doe.gov/erec/factsheets/geo_heatpumps.html#sidebar
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Benefits of a GHP
System
•
•
•
•
•
•
•
•
Low Energy Use
Free or Reduced-Cost Hot Water
Year-Round Comfort
Low Environmental Impact
Durability
Reduced Vandalism
Zone Heating and Cooling
Low Maintenance
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Solar Heating and
Cooling
• Most American houses receive
enough solar energy on their roof to
provide all their heating needs all
year!
• Active Solar
• Passive Solar
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Passive Solar
• A passive solar system uses no
external energy, its key element is
good design:
• House faces south
• South facing side has maximum
window area (double or triple
glazed)
• Roof overhangs to reduce cooling
costs
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• Thermal mass inside
46
Passive Solar
• Deciduous trees on the south side to
cool the house in summer, let light in
in the winter.
• Insulating drapes (closed at night
and in the summer)
• Greenhouse addition
• Indirect gain systems also such as
large concrete walls to transfer heat
inside
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Passive Solar Heating
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Passive Heating
Direct
Gain
Thermal
W all
Passive Cooling
Shading
Storage Suns pace
Ve nt ilat io n
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Earth Contact
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Active Solar Heating
• Flat plate collectors are usually
placed on the roof or ground in the
sunlight.
• The sunny side has a glass or plastic
cover.
• The inside space is a black
absorbing material.
• Air or water is pumped (hence
active) through the space to collect
the heat.
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Active Solar
Heating
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Flat Plate Collector
• Solar Collectors
heat fluid and the
heated fluid heats
the space either
directly or
indirectly
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Efficiency of Furnace
• The "combustion efficiency" gives you a
snapshot in time of how efficient the
heating system is while it is operating
continuously
• The "annual fuel utilization efficiency"
(AFUE) tells you how efficient the system
is throughout the year, taking into account
start-up, cool-down, and other operating
losses that occur in real operating
conditions.
• AFUE is a more accurate measure of
efficiency and should
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Efficiencies of Home
Heating
.
110
100
U.S. stock
7
90
80
70
1975-1976 building practice
(NAHB)
5
60
LBL standard
(medium infiltration)
50
LBL standard
(low infiltration)
40
3
30
Brownell
20
Mastin
10
Phelps
0
0
2000
4000
Saskatoon
Ivanhoe Pasqua
Leger
8000
1
Saskatchewan house
Balcomb
6000
Btu/ft2 per degree day
Annual fuel input for
space heat (106 Btu/1000 ft2)
9
10,000
1 Btu/ft 2 per degree day
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Degree days (base 65°F)
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Tips (Individual) to Save
Energy and Environment
• Set your thermostat as low as is comfortable in
the winter and as high as is comfortable in the
summer.
• Clean or replace filters on furnaces once a
month or as needed.
• Clean warm-air registers, baseboard heaters,
and radiators as needed; make sure they're not
blocked by furniture, carpeting, or drapes.
• Bleed trapped air from hot-water radiators once
or twice a season; if in doubt about how to
perform this task, call a professional.
• Place heat-resistant radiator reflectors between
exterior walls and the radiators.
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• Use kitchen, bath, and other ventilating fans
wisely; in just 1 hour, these fans can pull out a
houseful of warmed or cooled air. Turn fans off
as soon as they have done the job.
• During the heating season, keep the draperies
and shades on your south-facing windows open
during the day to allow sunlight to enter your
home and closed at night to reduce the chill you
may feel from cold windows. During the cooling
season, keep the window coverings closed
during the day to prevent solar gain.
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• Close an unoccupied room that is isolated from
the rest of the house, such as in a corner, and
turn down the thermostat or turn off the heating
for that room or zone. However, do not turn the
heating off if it adversely affects the rest of your
system. For example, if you heat your house with
a heat pump, do not close the vents—closing the
vents could harm the heat pump.
• Select energy-efficient equipment when you buy
new heating and cooling equipment. Your
contractor should be able to give you energy fact
sheets for different types, models, and designs
to help you compare energy usage. Look for high
Annual Fuel Utilization
Efficiency
(AFUE) ratings58
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