Building Heat Gains

7/24/2019 Building Heat Gains

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05/04/2011 1Tarik al-Shemmeri 1

Buildings Heat Gains


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SOURCES OF THERMAL ENERGY

TRANSFER FOR BUILDINGS

Generally, there are FOUR heat transfer

sources within any building, they are:

Fabric: Heat losses

Ventilation: Heat loss

Solar: Heat gains

Internal: Heat gains


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Solar Heat gains

FOR BUILDINGS

Solar heat gain through

windows and/or walls provides

a valuable contributionof space heating.


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The solar heat gain through a glazed area is

calculated by:QSolar = Area of window

x solar intensity

x Transmissivity.

Solar Heat gains

FOR BUILDINGS


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Casual Heat gains

FOR BUILDINGS

Casual heat gains inside a building provide a

valuable source of heat contribution to space

heating. Sources include :

occupants

lights equipments


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Casual Heat gains

FOR BUILDINGS


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Casual Heat gains

FOR BUILDINGS

Type of Heat Source Typical Heat Emission

Adults:

Sleeping 80W

Seated quietly 120W

Walking slowly 230W

Medium work 265W

Heavy work 570W



Casual Heat gains

FOR BUILDINGS

adult male 100%

child ( male, or female) 75female ( adult ) 85

old people ( male, or female) 80



Casual Heat gains

FOR BUILDINGS



Casual Heat gains

FOR BUILDINGS

Type of Heat Source FROM

LIGHTS

Typical Heat Emission

Fluorescent @ 400 lux 20W/m2floor area

Tungsten @ 200 lux 40W/m2

floor area



Casual Heat gains

FOR BUILDINGS



Casual Heat gains

FOR BUILDINGS

Typical Heat Emission

Desktop computer 150W

Computer printer 100W

Visual display unit 200W

Photocopier 800W

Hair dryer 800W

Domestic fridge-freezer 150W

Colour TV 100W

Hi-fi unit 100W

Toaster 500W

Oven 2500W

Electric and Electronic Equipment:



TUTORIAL EXAMPLES



WORKED EXAMPLE

20m

5m

10

m

W W

D

THE building shown has thermal data as indicated in the table; It is used for a

5-a-side game of football, there are 50 forty watts lights, switched on

continuously, and a 1.5 kW heater inside the hall. Determine the heating load

for this building, when the internal and external temperatures are 20 and zero

degrees centigrade.



Element U-value

W/m

2

K

Area

m

2

Temp.

Difference (

o

C)

Heat loss

WDoor 2 6

Windows 3 12 total

Walls 0.5

Roof 0.45

Floor 0.45

Fabric heat loss = TOTAL ( Doors, Windows, Walls, Roof & Floor) =

Ventilation Heat Loss = 0.335 N V T

Heat gains from occupants

Heat gains from lights

Heat gains from machines

Net heat transfer for the building

WORKED EXAMPLE



SOLUTION EXAMPLEElement U-value

W/m2K

Area

m2

Temp.

Difference(oC)

Heat loss

W

Door 2 6 20 240

Windows 3 12 total 20 720

Walls 0.5 282 20 2820

Roof 0.45 200 20 1800

Floor 0.45 200 0 0

Fabric heat loss = TOTAL ( Doors, Windows, Walls, Roof & Floor) =

-5580

Ventilation Heat Loss = 0.335 N V T =

-6700

Heat gains from occupants = No. of people x energy/person =

+600Heat gains from lights = No. of lights x wattage =

+2000

Heat gains from machines = No. of machines x output =

+1500

Net heat transfer for the building =

- 8180 W


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What do we need Light for:

Visual clarity and color perception

Reduced eye strain and fatigue

Greater learning ability and intelligence

Enhanced mental awareness, concentration and productivity


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Light bulbsas we know them, were invented by Thomas Edison in the late

19th century. They are extremelyinefficient systems. Their

main goal is to provide light, over 95% of the energy in anincandescent bulb is released as heat. Less than 5% of the

electricity going into your light bulb is being turned into light.There is a littlebit of room for improvement there.


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Mysore palace, lit up by 27,000 light bulbs - Southern India


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ORDINARY light bulbs are to be banned across

the European Union within two years in the

fight against climate change. The 490 millioncitizens of the 27 member states will be

expected to switch to energy-efficient bulbs

after a summit of EU leaders yesterday told the

European Commission to "rapidly submitproposals" to that effect. - Ian Johnston

Environmentalists said the change would save the public up to 5.4 billion a

year in fuel bills and also about 20 million tonnes of carbon emissions every

year.


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05/04/2011

2020 VISION on Energy:

The key EU targets and objectives:

A minimum 20 per cent EU cut in greenhouse

gas emissions by 2020, and a push for a

bigger cut of 30 per cent in future.

A target of 20 per cent energy efficiencysavings by 2020, requiring homes, offices and

streets to switch to energy-saving lighting.


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Tips - Energy Efficiency for Lighting

One Switch off all lights when not needed.

Two Label light switches to clearly identify the lights they control.

Three clean light fittings regularly. This will increase output and lead to fewer

lights being turned on.

Four Install modern slimline fluorescent tubes they will last much longer thanordinary bulbs and use less energy.FiveWhere double tubes have been fitted check whether one is sufficient.

SixMaximise natural lighting by ensuring windows are clean and window ledges

are not cluttered.SevenEnsure that your office layout considers the availability of natural and

artificial lighting.EightConsider fitting Presence Detectors



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05/04/2011


By switching off lights in rooms which arent being used you could cut your

lighting costs by as much as 15%


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Fit infra-red presence detectors to switch off lights when rooms or desksare unoccupied



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Tips Energy Efficiency for Lighting

Replace all light bulbs with energy efficiency recommended bulbs, which

will use around a quarter of the electricity and last up to 12 times longer!


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Clean windows

Documents

Building Heat Gains