EACR 1257: BUILDING SCIENCE
COURSE OUTLINE:
1. HEAT IN BUILDING
2. LIGHTING IN BUILDING
3. ACOUSTICS IN BUILDING
REFERENCE:
ENVIRONMENTAL SCIENCE IN BUILDING BY RANDALL MCMULLAN MSC, CPHYS,
MCIGB, MLNSP FOURTH EDITION, 1998
1. HEAT
a. Principles of Heat
- Nature of heat
- Heat transfer
- Gases and vapours
- Refrigerators and heat pumps
c. Energy Use
Condensation
- Thermal comfort
- Heat losses
- Heat gains
buildings
- Heat balance
- Energy consumption
- Energy regulations
b. Thermal Insulation
- Insulating materials
- V-values
- Thermal bridging
- Structural temperatures
d. Ventilation, Humidity and
- Ventilation
- Humidity
- Condensation in
- Condensation conditions
Principles of Heat
 A good thermal environment is a major aspect in the successful performance of
a building.
 Both human beings and their buildings interact with the heat that surrounds them
and they also contribute to this heat.
 Topics that are relevant to thermal design include the requirements of human
comfort, the types of heat loss and heat gain by buildings, and the nature of
moisture in the air. Before these topics are considered, this chapter describes
the basic nature of heat, its measurement, and its effects.
 The properties of gases and their effects, such as refrigeration, are also studied.
NATURE OF HEAT
Heat energy
 The modern definition of heat that follows is a simple statement, but the
truth of the statement was not obvious in the past and confused ideas
about the nature of heat are still common.
 HEAT (H or Q) is a form of energy
 UNIT: joule (J).
 The joule is the standard SI unit of energy as used for measuring any
other form of energy.
 Other units of energy still found in use include the following units:
• calorie, where 1 cal = 4.187 J
• kilowatt hour, where 1 kWh = 3.6MJ
• British Thermal Unit, where 1 BTU = 1.055 kJ
 Heat energy is an internal molecular property of a material. Other forms of
energy include mechanical energy, electrical energy, and chemical
energy.
 These other forms of energy can all be converted to thermal energy.
 For example, the mechanical energy of moving surfaces is converted
to heat
by friction; electric currents flowing in conductors produce heat; and
combustion (burning) converts the chemical energy contained in
materials to heat.
 Thermal energy often forms an intermediate stage in the
production of other forms of energy. Most electrical energy, for
example, is produced by means of the thermal energy released in
the combustion of fuels.
 The thermal energy radiated from the Sun is also the origin of
most energy used on Earth including the fossil fuels, such as coal
Power
 Power is a measure of the rate at which work is done, or at which energy
is converted from one form to another.
Power (P) = Heat energy (H)/ time (t)
UNIT: watt (W)
By definition, 1 watt = 1 joule/second.
 The watt is often used in the measurement of thermal properties and it is
useful to remember that it already contains information about time and
there is no need to divide by seconds.
Temperature
 Temperature is not the same thing as heat. A red-hot spark, for example,
is at a much higher temperature than a pot of boiling water; yet the
water has a much higher heat 'content' than the spark and is more
damaging.
 TEMPERA TURE is the condition of a body that determines whether
heat shall flow from it
UNIT: degree Kelvin (K)
See also the definitions of temperature scales.
 Heat flows from objects at high temperature to objects at low
temperature. When there is no net heat transfer between two objects
they are at the same temperature.
Thermometers
 The human body is sensitive to temperature but it is unreliable for measuring
temperature. The brain tends to judge temperature by the rate of heat flow in
or out of the skin.
 So for example, a metal surface always 'feels' colder than a plastic surface
even though a thermometer may show them to be at the same temperature.
 A thermometer is an instrument that measures temperature by making use
of some property of a material that changes in a regular manner with
changes in temperature.
 Properties available for such use include changes in size, changes in
electrical properties such as resistance, and changes in light emissions.
Some of the more common types of thermometer are described below.
a. Mercury-in-glass thermometers
Mercury-in-glass thermometers use the expansion of the liquid metal
mercury inside a narrow glass tube. The mercury responds quickly to
changes in temperature and can be used between -39°C and 357°C, which
is the range between the freezing point and the boiling point of mercury.
b. Alcohol-in-glass thermometers
Alcohol-in-glass thermometers use coloured alcohol as the liquid in the glass
tube. Alcohol expands more than mercury and can be used between -112°C
and 78°C, which is the range between the freezing point and boiling point of
alcohol.
c. Thermoelectric thermometers
Thermoelectric thermometers use the electric current generated in a
thermocouple, which is made by joining two different metals such as iron and
constantan alloy. The current quickly varies with temperature and can be
incorporated in remote or automatic control systems.
d. Resistance thermometers
Resistance thermometers use the change in electrical resistance which
occurs when a metal changes temperature. Pure platinum is commonly used
and the changes in its resistance can be measured very accurately by
including the thermometer in an electrical circuit.
e. Optical pyrometers
Optical thermometers measure high temperature by examining the
brightness and colour of the light emitted from objects at high temperatures.
The light varies with temperature and is compared with a light from a filament
at a known temperature.
Temperature scales
 In order to provide a thermometer with a scale of numbers, two easily
obtainable temperatures are chosen as upper and lower fixed points. The
interval between these two points on the thermometer is then divided into
equal parts, called degrees.
 The properties of water are used to define two common fixed points - the
temperature at which ice just melts and the temperature of steam from
boiling water - where both are measured at normal atmospheric pressure.
Celsius scale
 The Celsius temperature scale numbers the temperature of the
melting point of ice as 0, and the boiling point of water as 100.
 CELSIUS TEMPERATURE (°c) is a point on a temperature scale
defined by reference to the melting point of ice and the boiling point of
water
UNIT: degree Celsius (°c)
 Degrees Celsius are also used to indicate the magnitude of a
particular change in temperature, such as an increase of 20°c. The
less correct term 'centigrade' is also found in use.
Thermodynamic scale
 Considerations of energy content and measurement of the expansion of
gases lead to the concept of an absolute zero of temperature.
 This is a temperature at which no more internal energy can be extracted
from a body and it occurs at - 273.16 °c .
 The absolute (or thermodynamic) temperature scale therefore numbers
this temperature as zero.
 The other fixed point for the thermodynamic scale is the triple point of
water; the temperature at which ice, water, and water vapour are in
equilibrium (0.01 DC).
• THERMODYNAMIC TEMPERATURE (T)
 Is a point on a temperature scale defined by reference to absolute zero
and to the triple point of water
UNIT: degree Kelvin (K)
The degree Kelvin is the formal SI unit of temperature but the degree
Celsius is also used in common practice.
The interval of a degree Kelvin is the same size as a degree Celsius,
therefore a change in temperature of 1 K is the same as a change in
temperature of 1 °c.
The general relationship between the two temperature scales is given
by the following formula.
T = (θ) + 273
where T = Thermodynamic temperature (K)
(θ) = Celsius temperature (°c).
Heat capacity
 The same mass of different materials can 'hold' different quantities of
heat. Hence water must be supplied with more heat than the oil in order
to produce the same rise in temperature.
 Water has a greater heat capacity than oil; a property that is not to be
confused with other thermal properties such as conductivity.
 The heat capacity of a particular material is measured by a value of
specific heat capacity, and table 1.1 gives values for a variety of
materials.
 The SPECIFIC HEAT CAPACITY (c) of a material is the quantity of
heat energy required to raise the temperature of 1 kg of that
material by 1 degree Kelvin (or 1 degree Celsius)
UNIT: J/kg K (or J/kg °c)
Table 1.1 Specific heat capacities
Material
Specific heat capacity J/kgK
Water
4190
Concrete and brickwork
3300
Ice
2100
Paraffin and oil
2100
Wood
1700
Aluminum
910
Marble
880
Glass
700
Steel
450
Copper
390
2100 Note: The values for particular building materials
vary.
Application of heat capacity (water)
 The heat capacity of water is higher than the heat capacities of most other
substances, so water is a good medium for storing heat.
 The temperatures on the planet Earth are stabilised by the huge quantities
of heat energy stored in the oceans and the presence of this water around
islands, such as the British Isles, prevents seasonal extremes of
temperature.
 In summer the water absorbs heat and helps to prevent air temperatures
rising; in winter the heat stored in the water is available to help prevent
temperatures falling.
 Heat exchange devices, such as boilers and heating pipes, also make use
of the high heat capacity of water for transferring heat from one place to
another.
Density
The heat capacities of different materials are compared on the basis of
equal masses. However, the same mass of different materials may occupy
different volumes of space, depending upon their densities.
Density (e) = Mass (M)/ Volume (V)
UNIT: kilogram per cubic metre (kglm
 Heavyweight masonry materials, such as brick, concrete, and stone, have
high densities.
 This means that relatively small volumes of these materials have a large
mass and therefore provide a relatively high heat capacity within a small
volume.
 An electric storage heater, for example, contains bricks which are heated
by cheap rate electricity and then hold this heat for use later in the day.
 The heat storage provided by the brick, concrete, and stone used in
construction is particularly relevant to the thermal behaviour of buildings,
as will be discussed later.
Change of state
 All matter is made from small particles called atoms and for most materials
the smallest particle that exists independently is a group of atoms which
are combined to form a molecule.
 The spacing of the molecules in a substance and the forces between them
determine the phase, or state of matter, of that substance.
 In the normal ranges of temperature and pressure there are three possible
states of matter and they have the basic characteristics given below.
Solid state: The molecules are held together in fixed positions; the
volume and shape are fixed.
• Liquid state: The molecules are held together but have freedom of
movement; the volume is fixed but the shape is not fixed.
• Gas state: The molecules move rapidly and have complete
freedom; the volume and shape are not fixed.
The state of a substance depends upon the conditions of temperature and
pressure which act on the substance. Consider, for example, the common
forms of iron, water, and oxygen.
 At certain temperatures a material will undergo a change of state and in this
change its energy content is increased or decreased.
The absorption of heat by a solid or a liquid can produce the following
changes of state:
Liquefaction

SOLID
Vaporisation
LIQUID
GAS
(Melting)
(Boiling, Evaporation)
The release of heat from a gas or a liquid can produce the following
changes of state:
Condensation
GAS
Solidification
LIQUID
SOLID
Fusion
Sensible and latent heat