4 Energy Use in Building（建筑能耗）

All buildings use energy for lighting, heating or cooli

ng.

This chapter explains the use of energy in buildings

and includes the technical basis for defining thermal

comfort.

The mechanisms for the heat loss and gains relati

ng to buildings are analysed and calculated

so that you can understand the energy use of partic

ular buildings.

this chapter describes:

4.1 Energy use

4.2 Thermal comfort 热舒适4.3 Heat losses 失热量4.4 Heat gains 得热量4.5 Heat balance 热平衡

4.6 Energy consumption 能耗

4.1 Energy use

4.1.1 Energy terms

（ 1 ） A fuel is a substance that is a source of energy

（ 2 ） fossil fuels 化石燃料 coal, crude oil and natural gas

（ 3 ） non-renewable energy 不可再生能源 is from sources which can only use once fossil fuels

（ 4 ） renewable energy 可再生能源 is from sources which are replenishable 可补给的 wind power, wave power 潮汐能

（ 5 ） primary energy 一次能源 is the total energy contained in natural reserves coal ， oil ， natural gas（ 6 ） transformation 能源的转化Is an activity that converts primary energy into another formFuels to electricity, crude oil to petroleum（ 7 ） secondary energy 二次能源Is the energy contained in a fuel which results from a transfor

mation process.Electricity, manufactured gas, surplus hot water（ 8 ） delivered energy 输出能源Is energy content as it is received by the consumer.Pay for money（ 9 ） useful energy 有用能Is the energy required to perform a given task.

4.1.1 Energy units

The scientific unit of energy is the joule.

Megajoules 1MJ=106J

Gigajoules 1GJ=109J

Tonne of oil equivalent 吨石油当量1 tonne of oil equivalent = 41.87gigajoules

= 107kilocalcories

= 11630 kWh

= 396.8 therms

4.4.1 calorific values 热值

Calorific value is a measure of the primary heat energy content of a fuel expressed in terms of unit mass or volume.

Some typical calorific values are quoted in table 4.1

Table 4.2 shows typical use of energy on the large scale of national usage.

4.2 Thermal comfort

The body constantly produces heat energy from the food energy it consumes.

This heat needs to be dissipated （散失散失） at an appropriate rate to keep the body at constant temperature.

The transfer of the heat from the body is mainly by the processes of convection, radiation and evaporation.

The thermal comfort of human beings governed by many physiological( 生理学生理学的的 )mechanisms of the body ,Vary from person to person.

Are you or your employees feeling uncomfortable with the temperature in the workplace?

The term ‘thermal comfort’ describes a person’s state of mind in terms of whether they feel too hot or too cold.

There’s more to it than just room temperature.

4.2.1 Factors affecting thermal comfort

Personal variables Activity Clothing Age Sex

Physical variables Air temperature Surface temperature Air movement humidity

The Six Basic Factors

The greater the activity of the body the more heat it gives off.

The rate of heat emission depends upon the individual metabolic rate （代谢率代谢率） of a person and upon their surface area.

The average rate of heat emission decreases with age.

Table 3.1 lists typical heat output from an adult male for a number of different activities.

The output from adult females is about 85% thatis about 85% that of males.

4.2.1 Activity

Clothes act as a thermal insulator for the body and help to maintain the skin at a comfortable temperature.

a scale of clothing （服装的数值体系服装的数值体系） has been developed: the clo-value.

1clo=0.155m1clo=0.155m22K/W K/W of insulation and values range form 0clo to 4clo.

Table 3.2 shows the value of different types of clothing and indicates how the room temperature required for comfort varies with clothing.

4.2.2 Clothing

When sitting near

the cold surface of

a window, do you feel

comfort? Why?Different types of temperatures are described below Inside air temperature tai 室内空气温度室内空气温度 Mean radiant temperature tr 平均辐射温度平均辐射温度 Inside environmental temperature tei 室内环境温度室内环境温度 Dry resultant temperature tres ???? ???? 温度温度 Room centre comfort temperature tc 房间中心舒适温度房间中心舒适温度

4.2.3 Room temperature

（ 1 ） Inside air temperature tai

室内空气温度室内空气温度

The inside air temperature is the average temperature of the bulk air inside a room .

It is usually measured by an ordinary dry bulb thermometer which is suspended in the centre of the space and shielded from radiation.

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.....tAtAt

21

2211r

（ 2 ） Mean radiant temperature tr

平均辐射温度平均辐射温度 The mean radiant temperature is the average effect

of radiation from surrounding surfaces.

The mean radiant temperature should be kept The mean radiant temperature should be kept near the air temperature but not more than 3 near the air temperature but not more than 3 ℃ below it, otherwise conditions are sensed ℃ below it, otherwise conditions are sensed as “stuffy”as “stuffy”

（ 3 ） Inside environmental temperature tei

室内环境温度室内环境温度 Inside environmental temperature Is a

combination of air temperature and radiant temperature. The exact value depends upon convection and radiation effects.

For average conditions it can be derived from the following formula

airei 3t/13t/2t

Environmental temperature is recommended Environmental temperature is recommended for the calculation of heat loss and energy for the calculation of heat loss and energy requirementsrequirements

（ 4 ） Dry resultant temperature tres

室内综合温度室内综合温度

Is a combination of air temperature, radiant temperature and air movement.

When the air movement is low it can be derived form the following formula

airres 2t/12t/1t

（ 5 ） Room centre comfort temperature tc

房间中心舒适温度房间中心舒适温度 Is a measure of temperature which gives an acceptabl

e agreement with thermal comfort. When air movement is low, the dry resultant temperat

ure at the centre of a room is commonly-used comfort temperature

The globe thermometer 黑球温度计 is a regular thermometer fixed inside a blackened globe of specified diameter

This globe temperature can be used to calculate other temperatures and when air movement is small it approximates to the comfort temperature.

球体 , 地球仪 , 地球 , 世界

The movement of air in a room helps to increase heat lost from the body by convection

Can cause the sensation of draughts Air movement above 0.1m/s in speed require higher air t

emperature to give the same degree of comfort Measure air movementMeasure air movement A hot-wire anemometer and a Kata thermometer

热线流速计 卡塔温度计（冷却温度表） May be used to measure air movement.

Both devices make use of the cooling effect of moving air upon a thermometer.

4.2.4 Air movement 空气流速

Humidity is caused by moisture in the air Relative humidity within the range of 40-70% is required fo

r comfortable conditions1 High humidities and high temperatures

→ feel oppressive ( 难以忍受的 ) → natural cooling by perspiration( 排汗 )is decreased2 High humidity and low temperature → cause the air to feel chilly3 Low humidity

→ dryness of throats and skin Static electricity

4.2.5 Humidity 湿度

Ventilation Is necessary to provide oxygen and to remov

e contaminated （受污染的）（受污染的） air

Ventilation Has a great effect on the heat loss from build

ings and condensation in buildings

A number of statutory regulations （法定规章）法定规章） specify

minimum rates of air supply in occupied spaces.

Table 3.4 gives some typical fresh air-supply rates

Statutory 法令的法令的 , , 法定的法定的 Statutory regulations 法定规章法定规章

4.2.6 Ventilation 通风

4.2 Thermal comfort

4.2.1 activity4.2 .2 clothing4.2. 3 room temperatures Inside air temperature tai 室内空气温度室内空气温度 Mean radiant temperature tr 平均辐射温度平均辐射温度 Inside environmental temperature tei 室内环境温度室内环境温度 Dry resultant temperature tres 室内综合温度室内综合温度 Room centre comfort temperature tc 房间中心舒适温度房间中心舒适温度4.2.4 air temperature 4.2.5 humidity 4.2.6 ventilation

Factors affecting thermal comfort

Factors affecting thermal comfort

4.3 Heat losses 失热量4.3.1 Factors affecting heat loss

Figure 3.1 Heat losses from a building

Some important factors are listed below

Insulation of building

Area of the external shell 建】房屋的框架 Temperature difference

Air change rate 换气率 Exposure to climate

Efficiency of services

Use of building

4.3.2 Calculation of heat loss 失热量计算

Fabric heat lossFabric heat loss 结构失热量 Fabric heat loss from a building is caused by the transmi

ssion of heat through the materials of walls, roofs and floors.

Assuming steady state conditions, the heat loss for each element can be calculated by the following formula.

tUAfP

Ventilation loss Ventilation loss 通风失热量通风失热量

3600

t NVCV VP

Ventilation heat loss from a building is caused by the loss of warm air and its replacement by air that is colder and has to be heated.

External temperature External temperature 室外温度室外温度

When designing heating system of buildings it is necessary to a

ssume a temperature for the outside environment temperature

In winter: = outside air temperature for design purposeIn winter: = outside air temperature for design purpose

For heat transfer calculation in summer it is necessary to take a

ccount of solar radiation as well as air temperature.

In summer: = sol-air temperature tIn summer: = sol-air temperature teoeo

sol-air temperature （室外空气综合温度）is an environmental temperature for the outside air

which include the effect of solar radiation

1 。围护结构外表面的热平衡图

太阳辐射

长波辐射换热量

对流换热量

2 。建筑物外表面单位面积上

得到的热量：

)()(

)(

wzoutwout

lw

outairout

lwwairout

tttQaI

t

QaIttq

太阳太阳直射直射辐射辐射大气大气

长波长波辐射辐射

太空太空散射散射辐射辐射

对对流流换换热热

地面反射地面反射辐射辐射

环境长波辐射环境长波辐射

地面地面长波长波辐射辐射

壁体得热壁体得热

式中 —建筑物外表面单位面积上得到的热量， W/m2 — 围护结构外表面的对流换热系数， W/ m2℃ — 室外空气温度，℃ — 围护结构外表面温度，℃ — 围护结构外表面对太阳辐射的吸收率 — 太阳辐射照度， W/ m2 — 围护结构外表面与环境表面的长波辐射换热量， W/ m2

)()(

)(

wzoutwout

lw

outairout

lwwairout

tttQaI

t

QaIttq

qout

airt

wtaI

lwQ

太阳太阳直射直射辐射辐射大气大气

长波长波辐射辐射

太空太空散射散射辐射辐射

对对流流换换热热

地面反射地面反射辐射辐射

环境长波辐射环境长波辐射

地面地面长波长波辐射辐射

壁体得热壁体得热

Worked example 4.1

A window measuring 2 m by 1.25 m has an average U-value, including the frame, of 6.2 W/m2K. Calculate the rate of fabric heat loss through this window when the inside comfort temperature is 20 and the out ℃side air temperature is 4 .℃

know U= 6.2 W/m2K A=2X1.25=2.5m2 t=20-4=16 ⊿ ℃

using

So fabric loss=248W

248165.22.6Pf tUA

Worked example 4.2

A simple building is 4 m long by 3 m wide by 2.5 m high. In the walls there are two windows, each 1 m by 0.6 m, and there is one large door 1.75 m by o.8 m.

The construction has the following U-values in W/m2K: windows 5.6, door 2.0, roof 3.0, floor 1.5.

The inside environmental or comfort temperature is maintained at 18 while the outside air temperature is 6 . The ℃ ℃volumetric specific heat capacity of the air is taken to be 1300J/m3 . There are 1.5 air change per hour. ℃

Calculate the total rate of heat loss for the building under the above conditions.

Step1: sketch the building with its dimensions, as in figure 3.2. calculate the areas and the temperature difference.

Step 2: tabulate the information and calculate the rate of fabric heat losses using

Step3: calculate the ventilation heat loss.

CV= 1300J/m3 , N=1.5/h V=4X3X2.5=30m℃ 3, t=18-6=12 ⊿ ℃

using

tUAfP

1953600

12305.113003600

t NVCV

VP

So rate of ventilation heat loss = 195W

Step4: total rate of heat loss = fabric heat loss + ventilation heat loss= 1734.24+195=1929.24W

4.3.3 Non-steady condition 非稳定条件 For situations where the steady state assumption is

invalid, it is necessary to consider the effects of Cyclic (daily) variations in the outside temperature, Variations in solar radiation and Changes in the internal heat input

Thermal admittanceThermal admittance （蓄热系数）（蓄热系数） or Y-valueor Y-value is a prope is a property of an element (rty of an element ( 构件）构件） or a room which controls fluor a room which controls flu

ctuations(ctuations( 波动波动 )) in the inside temperature. in the inside temperature. UnitUnit ： W/m2K

Heavyweight structures have smaller temperature swings(( 温度波动 温度波动 )) than lightweight structures.

Figure 3.3 thermal response damping 阻尼， 减幅 , 衰减

Thermal transmittance Thermal transmittance 传热系数传热系数

Figure 4.3 Thermal response

McMullan

For very thin units, such as glass, the admittance becomes the same as the U-value.

传热系数和蓄热系数是相反的概念。传热系数表示热传导的能力，蓄热系数表示储存热量的能力。

4.3 Heat loss4.3.1 factors affecting heat loss4.3.1 factors affecting heat loss Insulation of building Area of the external shell 建】房屋的框架 Temperature difference Air change rate 换气率 Exposure to climate Efficiency of services Use of building 4.3.2 calculation of heat loss4.3.2 calculation of heat lossFabric heat loss

Ventilation loss

tUAfP

3600

t NVCV VP

This is about what we we did last lesson. Do you remember?

Now I want some one to summary in Chinese.

4.3.3 Non-steady condition 4.3.3 Non-steady condition 非稳定条件非稳定条件

Thermal admittance （蓄热系数） or Y-value

4.4 Heat gains

Figure 4.4 Typical heat gains in a building

McMullan

typical heat gains in a building

11 ）） Solar heat gains from the sunSolar heat gains from the sun

22 ）） Casual heat gains from occupants and equipmCasual heat gains from occupants and equipm

ent in the buildingent in the building

11 ）） Solar heat gains from the sunSolar heat gains from the sun

Depends on many factors

Table 4.9 seasonal solar gain through windows

Sun controlsSun controls to Prevent excessive heat gain and

glare （眩光） caused by direct sunshine.

External controls （外遮阳）Internal controls （内遮阳）Special glasses （特殊玻璃）

公共建筑可调节的金属材质遮阳装置

External controls

External controls

22 ）） Casual heat gains from occupants and Casual heat gains from occupants and equipment in the buildingequipment in the building

Heat from people

Heat from lighting

Heat from cooking and water heating

Heat from machinery, refrigerators , electrical appliances

Table 4.11 domestic seasonal heat gainsTable 4.11 domestic seasonal heat gains Now I want you to turn to page 81

Now we will go on 4.5 Heat balance

The thermal comfort of humans requires that the inside temperature of a building is kept constant at a specified level, and the storage of goods also needs constant temperatures.

In order to maintain constant temperature the building will generally require heating or cooling, and both of these process involve the consumption of energy.

Calculation of energyCalculation of energy PtE

Heat balance

Fabric

Heat

Losses

ventilation

Heat

Losses

solar

Heat

gains

casual

Heat

gains

Energy for heating or cooling

++ = + +

This is a general expression of balance which is true for summer and winter conditions.

Seasonal energy requirements季节性能耗

The energy requirement of a building at any particular time depends on the state of the heat losses and the heat gains at the same time.

These factors vary but it is useful to consider the total effect over a standard heating season.

It is important to note that the calculation of seasonal heat losses and gains assumes average temperature conditions and can not be used to predictcan not be used to predict the size of the heating or cooling plant required;

such a prediction needs consideration of the coldest and hottest days.

Seasonal heat calculations are valid forare valid for calculating total energy consumption and can be used to predict the quantity of fuel required in a season and how much it will cost.

Worked example 4.3

Over a heating season of 33 weeks the average rate of heat loss from a certain semi-detached housesemi-detached house （半独立半独立式住宅式住宅） is 2500W for the fabric loss and 1300W for the ventilation loss. The windows have areas:

6m2 south-facing, 5m2 east-facing, 6m2 north-facing.The house is occupied by three people and cooking is by ga

s.Use the values for seasonal heat gains given in table 3.7 and

3.9 and calculate :(a) The seasonal heat losses(b) The seasonal heat gains; and (c) The seasonal heat requirements.

(a) total rate of heat loss= fabric loss+ ventilation loss

= 2500W+1300W=3800W

heat energy lost= rate of heat loss × time taken

=3800W × (33×7 ×24 ×60 ×60)s

= 75.842GJ(giga joules) 千兆焦千兆焦 so seasonal heat loss = 75.842GJ

=75842MJ(mega joules) 兆焦兆焦

(b) Heat gains solar window gain ( table 3.7)solar window gain ( table 3.7) south (680MJ/m2×6) 4080 east (410MJ/m2×5) 2050 north (250MJ/m2×6) 1500 casual gains ( table 3.9)casual gains ( table 3.9) body heat ( 1000MJ×3) 3000 cooking (gas) 6500 water heating 2000 electrical 3000 total 22130MJtotal 22130MJSo seasonal heat gain=22130MJ

(c) Seasonal heat requirement = heat loss- heat gainheat loss- heat gain

=75842-22130

=53712MJ(mega(mega joulesjoules 兆兆焦焦 ))

=53.712GJ(giga joules(giga joules 千兆千兆焦焦 ))

Efficiency 效率

The heat energy required for buildings is commonly obtai

ned from fuels such as coal, gas and oil, even if the ener

gy delivered in the form of electricity.

Each type of fuel must be converted to heat in an approp

riate piece of equipment

The amount of heat finally obtained depends upon the or

iginal heat content of the fuel and the efficiency of the sy

stem in converting and distributing （分配） this heat.

Efficiency 效率

Efficiency is a measure of the effectiveness of a system which converts energy from one form to another

Domestic heating efficiency →table 4.12 Delivered energyDelivered energy （供给能量）（供给能量） Useful energyUseful energy （有用能（有用能）

energy delivered

energy useful

100

%efficiency

Worked example 4.4

The seasonal heat requirement of a house is 54GJ, which is to be supplied by a heating system with an overall house efficiency of 67%. The solid fuel used has a calorific value of 31MJ/kg. calculate the mass of fuel required for one heating season.

Efficiency = 67/100, output= 54MJ, input energy=?

Using

energy delivered

energy useful

100

%efficiency

energyinput

54

100

67

Input energy = 80597MJ

Mass of fuel needed=

2600kg

31MJ/kg

80597MJ

valuecalorific

requiredenergy

4.6 Energy regulations 能源规范

Why do we need energy regulations?

Can help to minimise energy use in buildings

Regulation about thermal insulation

control heat loss from buildings

Minimise the heat load for heating in winter

Minmise the cold load for air conditioning in summer

there are many regulations

4.6.1 Building regulations 建筑规范

Encourage or enforce energy efficiency in buildingsHow to realize energy efficiency in buildings by regulations?The regulations achieve this aim by controlling the following (1) Heat loss by transmission through the fabric(2) Heat loss by air leakage around openings and through

the fabric(3) Control system for space heating and hot water(4) Heat loss from vessels and pipes used for water(5) Heat loss from hot water pipes and hot air ducts used for

space heating(6) energy-efficient lighting sources and switching for the

lighting

Also should consider:

Other essential performances such as structural

stability, resistance to rain penetration and

overheating

The need for design details that are practical and

within the capabilities of the construction workforce

Building services that are easy for occupiers to

manage successfully

Regulations which are not too complex to interpret

and enforce

4.6.2 Energy rating, SAP 用能评级

The overall energy efficiency of a dwelling , such as a house,

can be given an Energy Rating by using a Standard Asses

sment Procedure (SAP)

An SAP Energy Rating of a dwelling is found by using a stan

dard method method to calculate the annual energy cost f

or space heating and water heating in the building

SAP Energy Ratings are expressed on a scale of 0 to 100,

The higher the SAP number the better the performance

4.6.3 Carbon Index ， CI 碳指数The Carbon Index (CI) is an energy rating

based on the overall carbon dioxide emission figure for a building

Carbon Index energy ratings are calculated using the information for a SAP rating and expressed on a scale of 0 to 10,

The higher the CI the better the performance.

4.6.4 Insulation of the building fabric 围护结构保温

（ 1 ） Elemental method 构件法Matching of standard U-values for individual const

ruction elements

Table 4.13 Elemental U-values for fabric insulation

（ 2 ） Target U-value method 目标 U 值法

Compare the average U-value of the whole exposed fabric with a specified target U-value

This method offers greater design flexibility than elemental method

They are subject to poorest acceptable U-values that are specified for each element

Also subject to limitations on thermal bridging and air infiltration.

（ 3 ） Carbon index method 碳指标法

This method also offers design flexibility.

Buildings with higher carbon index values will satisfy regulations

They are subject to poorest acceptable U-values that are specified for each element

Also subject to limitations on thermal bridging and air infiltration.

（ 4 ） Commercial buildings 商业建筑

For buildings other than dwellings the design, construction and operation, needs to demonstrate that the building and its services are energy efficient.

They are subject to poorest acceptable U-values that are specified for each element

Also subject to limitations on areas of openings.

4.6.5 Other measurements for energy conservation 其他节能措施

Controlling the insulation of the building fabric Thermal bridging around openings Infiltration Space heating control Hot water controls and insulation of storage lighting

Translate into Chinese

metabolic rate

Stack effect

Non-renewable energy

Renewable energy

Primary energy

Secondary energy

Calorific values

Dry resultant temperature

sol-air temperature

Air change rate Thermal admittance

1 SAP Energy Ratings are expressed on a

scale of ( )

A 0 to 1.0

B 0 to 10

C 0 to 100

D 0 to 100%

2 Carbon Index energy ratings are calculated using the information for a SAP rating and expressed on a scale of ( )

A 0 to 1.0

B 0 to 10

C 0 to 100

D 0 to 100%

3 ( ) may contribute to energy efficiency

A Controlling the insulation of the building fabric

B avoid Thermal bridging around openings

C mimise Infiltration

D Space heating control

E Hot water controls and insulation of storage

F energy-efficient lighting source and control

4 Casual heat gains in a building include ( )

A heat from people

B heat from lighting

C heat from sun

D heat from cooking and water heating

E heat from machinery, refrigerators

F heat from electrical appliances