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Page 1 Low Energy Building Components.doc/14/11/2010

LOW ENERGY BUILDING COMPONENTS

Designing Energy Efficient Homes

Ar Chan Seong Aun.M Arch (Distinction), B Arch (Hons), B Bdg Sc (VUW, NZ), APAM, AIPDM, TAM.

Pertubuhan Arkitek Malaysia

Centre for Environment, Technology & Development Malaysia

CPD Seminar 18th September 2004

1. ENERGY SUPPLY & DEMAND IN MALAYSIA

2. ENERGY USE IN MALAYSIAN HOMES2.1 Energy Indices2.2 End Use & Actual Energy Consumption

3. LOW ENERGY BUILDING COMPONENTS3.1 Site Planning & Microclimate3.2 Orientation, layout planning, Size, Shape & Building Type3.3 Roof Systems3.4 Wall Construction & OTTV3.5 Window Systems

4. REFERENCES


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1.ENERGY SUPPLY & DEMAND IN MALAYSIA

The local power sector is currently one of the country's most highly subsidised industries.The price of natural gas has been fixed at RM6.40 per mmbtu since 1997. This represents a

76% discount to average US rates of US$6.39 per mmbtu converted at the prevailingexchange rate. Thus far, the discount has been borne by Petroliam Nasional Bhd (Petronas) inthe form of loss of revenue. The Star 3rd July 2004.

The price was up for review in 2000 (following the expiry of the Gas Supply Agreement)when Petronas started pushing hard for an upward revision. In the end, the rate wasmaintained as any increase would be detrimental to TNB (The utility company has not seen atariff increase since 1997 when the average rate increased by 9.5% to 23.5 sen per kilowatt-hour). The gas price is scheduled for its next review at end-2005.

With about 71% of power stations relying on natural gas as an energy source in 2001,electricity rates can not be expected to remain stagnant if gas prices go up. If the governmentwere to remove the gas subsidy completely and allow Petronas to charge international marketrates of around RM24.70 per mmbtu, TNB would have to raise its average tariff rate bysome 25% in order to maintain its FY05 net profit forecast of RM1.6bil, according toAvenue Securities power analyst Daniel Griffin. Electricity rates have been kept low, to the

extent that Malaysia's are now the second lowest in Asia, as a means of attracting foreigndirect investment into the country. As a result, the industrial sub-sector is now the mostheavily subsidised. It is highly unlikely that the government will instantly allow Petronas torevise gas prices according to international market rates as that would have an adverse effecton Malaysia's current competitive advantage, the analyst says.


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The residential and commercial sector consumed about 48% of total electricity generated.With increasing GDP, electricity demand will increase but in different proportions.Malaysian electricity-GDP elasticity is around 1.5 meaning for every 1% rise in GDP,electricity consumption increases by 1.5%. A comparison of the 1990 energy use per capitaoutput by DANIDA has Malaysia at about 26 GJ/1000USD compared to Thailand at 20GJ/1000USD and Japan at 7 GJ/1000USD. We are obviously not using our energy veryefficiently.


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Based on current economic growth rates, PTM or Pusat Tenaga Malaysia have projected thatMalaysia would become a net imported of energy by between 2010 and 2015. Knowingthis, can we as responsible Architects continue to take the cheap fossil fuel approach to ourbuilt environment?

Summary

1. Electricity tariffs are expected to increase by around 25% sometime after 20052. Malaysia will become a net imported of energy sometime between 2010 and 20153. Energy Efficiency Standards will become mandatory sometime before Malaysia

becomes a net energy imported.


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2. ENERGY USE IN MALAYSIAN HOMES

2.1 Energy IndicesBefore going into details of the quantum of energy use, some method of comparing energyuse - the energy use indices will be explained. The index selected would depend on the

intended application of the index and the normalizing factor. Among Architects thenormalizing factor for comparing buildings is the gross floor area. The most commonly usedindex for comparing energy use in buildings is therefore the Annual Area Energy Use Index -AEUI. This is usually expressed as kWh/m2/year which measure the total energy used in abuilding for one year in kilowatts hours divided by the gross floor area of the building insquare meters.

2.2 End Use & Actual Energy Consumption

The amount of energy used in buildings depends firstly on WHAT IT IS USED FOR. Thusthe initial and most important step in isolating the factors affecting energy use is to determineits end-use. To architects, the category of use or building type will be the first factor toconsider. Therefore to compare the energy index of say an office building which operatesfrom 9 am to 5 pm to say a data processing center which operates computers around the clockwould not be a reasonable comparison because the operating hours are different and thecomputers in the data processing centre would consume more electricity and may require ahigher environmental standard. Comparing two schools in the same climatic region andsimilar operating conditions would however give a comparison of the energy performance ofthe two buildings.

In Malaysia not much published data is available yet on the Energy Performance or actualannual energy consumption of buildings. Pusat Tenaga Malaysia - PTM is still in the processof auditing Government Office Buildings and Center for Environment, Technology &Development, Malaysia - CETDEM has received funding from DANIDA to pilot a study of

energy consumption in Malaysian Homes.


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Home consumption of energy would depend very much on the appliances installed, the hoursof use and the efficiency of the equipment. In a typical Malaysian terraced house of about180 m2, the refrigerator is usually the largest consumer of electricity while the airconditioning will increasingly become more important as living standards rise. The CETDEMsurvey should reveal clearer results for the future.

Refrigerator

38%

Rice cooker

3%Water Heater

14%

Washing Machine

17%

Iron

3%

Fan

2%

Television

1%

Radio

0%

Air Conditioner

21%

Fluorescent Lamps 18w

0%


1%

Vacuum Cleaner

0%

Refrigerator

Rice cooker

Water Heater

Washing Machine

Iron

Fan

Television

Radio

Air Conditioner



Vacuum Cleaner

Malaysian Home Energy Use Estimate - 180 m2 180

ITEM kW hrs/yr kWh kWh/m2/yr %

Refrigerator 0.3 8760 2628 14.6 38%

Rice cooker 0.65 360 234 1.3 3%

Water Heater 2.7 360 972 5.4 14%

Washing Machine 2.2 540 1188 6.6 17%

Iron 1 180 180 1 3%

Fan 0.045 3600 162 0.9 2%

Television 0.06 1080 64.8 0.36 1%Radio 0.25 72 18 0.1 0%

Air Conditioner 1 1440 1440 8 21%

Fluorescent Lamps 18w 0.032 288 9.216 0.0512 0%


Vacuum Cleaner 0.3 96 28.8 0.16 0%

TOTAL 8.729 17064 6980.112 38.7784


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In a home with 3 kW of installed air conditioning consisting of 3 units of about 1 HP each or2 units of 1.5 HP each, the air conditioning energy could be nearly half the total energyhousehold energy use.

Refrigerator

27%

Rice cooker

2%

Water Heater10%

Washing Machine

12%

Iron

2%

Fan

2%

Television

1%

Radio

0%

Air Conditioner

43%


0%


1%

Vacuum Cleaner

0%

Refrigerator

Rice cooker

Water Heater

Washing Machine

Iron

Fan

Television

Radio

Air Conditioner



Vacuum Cleaner

Malaysian Home Energy Use Estimate - 180 m2 1803 kW air conditioning

ITEM kW hrs/yr kWh kWh/m2/yr %Refrigerator 0.3 8760 2628 14.6 27%

Rice cooker 0.65 360 234 1.3 2%

Water Heater 2.7 360 972 5.4 10%

Washing Machine 2.2 540 1188 6.6 12%

Iron 1 180 180 1 2%

Fan 0.045 3600 162 0.9 2%

Television 0.06 1080 64.8 0.36 1%

Radio 0.25 72 18 0.1 0%

Air Conditioner 3 1440 4320 24 44%



Vacuum Cleaner 0.3 96 28.8 0.16 0%TOTAL 10.729 17064 9860.112 54.7784


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3. LOW ENERGY BUILDING COMPONENTS

3.1 Site Planning & Microclimate

The following topographic factors have been found by Geiger (3) to influence the

microclimate around a building, and ultimately its cooling energy requirement.

1. Altitude2. Terrain3. Water Body4. Natural Cover5. Cities

ALTITUDE Temperature in the atmosphere decreases with increasing altitude byapproximately 1 degree centigrade per 180 meters in the tropics and summer in the temperateregions and 1 degree centigrade per 220 meters in winter conditions

TERRAIN Cool air is heavier than warm air, and at night the outgoing radiation causes acool air layer to form near the ground surface. The cool air behaves somewhat like water,flowing towards the lowest point. This flow of cool air causes cool island or cool airpuddles to form in valleys.

Accordingly, elevations that impede the flow of air effect the distribution of nocturnaltemperatures by dam action and concave terrain formations become cool-air lakes at night.The same phenomenon is enlarged when a large volume of cool air flow is involved, as invalleys. The plateaus, valley walls and bottom surfaces cool off at night. Air flow occurstowards the valley floor. On the valley slopes, a series of small circulations mix with theneighboring warm air, causing intermediate temperature conditions. Accordingly, the

temperature at the plateaus will be cool, at the valley floors very cool, but the high sides ofthe slopes will remain warm. This area often indicated by the difference in vegetation, isreferred to as the warm air slope (thermal belt).

WATER BODY Water having a higher specific heat than land, is normally warmer inwinter and cooler in summer and usually cooler in during the day and warmer at night, thanland. Accordingly, the proximity of bodies of water moderates extreme temperaturevariations and lowers the peak temperatures in our tropical climate.

In the diurnal temperature variations, when the land is warmer than the water, low cool airmoves over the land to replace the updraft. During the day, such offshore breeze may have acooling effect of about 5 degree centigrade. At night the direction is reversed. The effect

depends on the size of the water body and are more effective along the lee side.

NATURAL COVER The natural cover of the terrain tends to moderate temperatures andstabilize conditions through the reflective qualities of various surfaces.

Plan and grassy cover reduce temperatures by absorption of insulation, and cool byevaporation. It is generally found that temperatures over grassy surfaces are 5 to 7 centigradedegrees cooler than those of exposed soil. Other vegetation may further reduce high


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temperatures; temperatures under a tree at midday can be 3 degrees centigrade lower than inthe unshaded environment.

Conversely, man-made surfaces tend to elevate temperatures, as the materials used areusually absorptive in character. Asphalt surfaces can reach 51 deg.C in 37 deg.C airtemperatures.

CITIES Cities tend to be warmer than the surrounding countryside. That cities differ fromthe country side not only in their temperatures but also in many other aspects of climate iswidely recognized. The city itself is the cause of these differences. Five basic influences set acitys climate apart from that of the rural area.

First, there is the difference in surface materials. The predominantly rocklike materials of thecitys buildings and streets can conduct heat about three times as fast as it is conducted bywet sandy soil. This means that the citys materials can accept more heat in less time, so thatat the end of a day the rock like material have stored more heat than an equal volume of soil.

Secondly, the citys structure have a greater variety of shapes and orientations and function

like amaze of reflectors, absorbing some of the solar radiation and directing much of the restto other absorbing surfaces, so that almost the entire surface of a city absorbs and stores heat.In forest and open areas on the other hand, the heat tends to be stored in the upper part ofplants. Since air is heated almost entirely by contact with warmer surfaces rather than bydirect radiation, a city is more efficient in using sunlight to heat large volumes of air.

Third, the city is a prodigious generator of heat. Among these are factories, cars and people.A study of Manhattan by Griffiths (4) suggested that the heat produced by combustion aloneis 2.5 times greater than the solar heat gain

Fourth, the city has a higher run-off of rain water. In the country, rain water remains on thesurface or immediately below it. The water is thus available for evaporation, which is ofcourse a cooling process. Because there is less opportunity for evaporation in the city, it losesless heat.

Finally, the city air has a heavy load of solid, liquid and gas contaminants. These tend toreflect sunlight, reducing the amount of heat reaching the surfaces, but they also retard theoutflow of heat resulting in higher peak temperatures.

3.2 Orientation, Planning Layout, Size, Shape & Building Type

Building orientation affects the air conditioning / heating energy requirements in two respects

by its regulation of then influence of two distinct climatic factors.1. Solar radiation and its heating effects on walls and rooms facing different directions2. Ventilation effects associated with the relation between the direction of the prevailing

winds and the orientation of the building.Of the two, solar influence on energy is the most significant in the tropics and is extensivelycovered by many others.


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The table below compares the approximate daily solar gain for some typical Malaysianhousing types.

SOLAR GAINS IN TYPICAL MALAYSIAN HOUSING TYPES

Single

StoreyTerrace

Double

StoreyTerrace Five StoreyFlats Eight StoreyApartments

Gross Floor Area 880 1,408 60,500 81,680

Unit Floor Area 880 1,408 750 850

Volume 14,080 18,304 665,500 898,480

Roof Area 1,012 792 12,100 10,210

Wall Area 484 968 28,050 47,872

Envelope Area 1,496 1,760 40,150 58,082

Roof/Envelope Area 68% 45% 30% 18%

Wall/Envelope Area 32% 55% 70% 82%

North-South Fronting

Roof Solar Gains 30 24 363 306

NS-Wall Solar Gains 5 10 198 356

EW-Wall Solar Gains 0 0 165 246

Total Solar Gains-kWh/day 35 33 726 908

Total Solar Gains-kWh/m2 0.04 0.02 0.01 0.01

East-West Fronting

Roof Solar Gains 30 24 363 306

NS-Wall Solar Gains 0 0 83 123

EW-Wall Solar Gains 10 19 396 711

Total Solar Gains-kWh/day 40 43 842 1,141

Total Solar Gains-kWh/m2 0.46 0.31 0.14 0.14

Increased Solar Gain Percent 14% 29% 16% 26%

For an intermediate single storey terraced houses, where the roof makes up nearly 70% of thebuilding envelope exposed to the sun, roof insulation becomes all important to keep the homecool. Orientation has less of an effect the difference in solar radiation for a north-south andeast-west facing being only about 14%

An intermediate double storey terrace house however has significantly more wall area andorientation will have a significant effect on the solar gain, being nearly 30% more for an east-west facing house.

For flats and apartments, depending on the aspect ratio and height of the building, an east

west facing building can have 16% to 40% more solar gain than a north-south facing block.What can the Architect do to reduce this solar heat gain? The following are some suggestedideas.

1. Orientate the largest wall areas in the north-south direction2. Locate service areas such as staircases, store rooms and service ducts in the east-west

external walls.


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3. Place as many service rooms on the roof top of flats as possible to reduce the solargain through the roof.

4. Sky lights should not be used. If roof ventilation is required, use a jack up roof facingthe north.

5. Shade east-west facing walls with large roof overhangs or plant shading trees in frontof them.

3.3 Roof System

The typical Malaysian terraced house receives most of its solar heat gain from the roof. Thisis because the horizontal surface receives the highest solar radiation, peaking at about 350Wh/m2 at mid-day in the tropical sun and it continues to receive the highest solar radiationlevel throughout the day. Add to that the higher ratio of roof to building envelope area; thetypical roof receives from 50% to 85% of the total solar radiation as shown in the tablebelow.

SOLAR GAINS IN TYPICAL MALAYSIAN HOUSING TYPESSingleStoreyTerrace

DoubleStoreyTerrace

Five StoreyFlats

Eight StoreyApartments

Gross Floor Area 880 1,408 60,500 81,680

Roof/Envelope Area 68% 45% 30% 18%

Wall/Envelope Area 32% 55% 70% 82%

North-South Fronting

Roof Solar Gains-kWh/day 30 24 363 306

Total Solar Gains-kWh/day 35 33 726 908

Roof/Total Solar Gains 86% 71% 50% 34%

East-West FrontingRoof Solar Gains-kWh/day 30 24 363 306

Total Solar Gains-kWh/day 40 43 842 1,141

Roof/Total Solar Gains 76% 55% 43% 27%

Reducing the solar heat gain through the roof should therefore be the first priority for keepingthe home cool. For sloping roofs the following if implemented correctly can reduce insidetemperatures by as much as 4 degrees centigrade.

1. Use lighter coloured roofing or better still slightly reflective type roofing.2. Apply aluminium foil insulation under the roof tile to reduce radiant heat gained by

the roofing from being radiated to the ceiling.

3. Ventilate the loft area above the ceiling and below the roof tiles. Measurements takenin this loft area have been found to go as high as 45 deg.C for outside air temperatureof 35 deg.C for not insulated roofs.

4. Apply a layer of rock wool insulation immediately above the ceiling to prevent theheat from the loft area fro being radiated and conducted into the living areaimmediately below the ceiling.


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Measurements by Lafarge Roofing have found peak temperatures differences between aroof insulated as above and an not insulated to be as much as 4.5 deg.C

For apartment buildings, although the roof area is not the largest building envelope area,depending on the building height, solar gain through the roof can be 25% to 45% of the totalsolar heat gain. It is therefore important to apply at least 50 to 100 mm of solid mineral woolor polystyrene insulation above the concrete slab.


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3.4 Wall Construction & OTTV

The properties of materials which affect the rate of heat transfer in and out of a building, andconsequently the air conditioning or heating energy requirements are.

1. Thermal Resistance2. Surface Convective coefficient

3. Absorptivity, Reflectivity and Emissivity4. Heat Capacity

In the building regulations of many countries, a design criterion for building envelope, knownas the overall thermal transfer value (OTTV), has been widely adopted. The OTTVrequirement, which applies only to air-conditioned buildings, is aimed at achieving the designof adequately insulated building envelope so as to cut down external heat gain and hencereduce the cooling load of the air-conditioning system. The OTTV concept takes intoconsideration the three basic elements of heat gain through the external walls of a building, asfollows.

1. heat conduction through opaque walls2. heat conduction through glass windows

3. solar radiation through glass windows

Singapores Building Control Authority (BCA) had imposed a maximum permissible OTTVof 45 W/m2 for their buildings. Below is an example from their handbook for OTTVcomputation. Based on recent Malaysian Government initiatives, the imposition of amaximum OTTV appears to be one possible method to improve energy consumption inbuildings.

Component b/k R

outside air

film

0.044

mosaic tile 0.012/1.298

0.009

brick wall 0.115/0.807

0.143

cementplaster

0.012/0.533

0.023

fibreglass 0.050/0.035

1.429

gypsumboard

0.012/0.170

0.071


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The recommendations by Assoc Prof Dr Ku Azhar Ku Hassan of University ScienceMalaysia should serve as a useful guide to Architects.

1. Horizontal shading devices is generally effective against high sun at both east and

west orientations2. Vertical shading is generally effective for south orientations3. Egg-crate shading devices is the generally effective for all the orientations

Summary

4. Site surrounded with proper landscaping and water bodies can reduce themicroclimate temperate from between 4 to 7 deg.C

5. North and South oriented walls receive between 100 to 130 wh/m2 of solar radiationcompared to 300 Wh/m2 for east and west facing walls. Depending on the building

type and shape, a north-south oriented building can receive approximately between15% to 30% less solar gain than an east-west oriented building.

6. Locate low occupancy rooms on the west side of the home such as store andstaircases.

7. The roof is the surface which receives the highest amount of solar radiation throughthe day. Insulating the roof is therefore vital in reducing air conditioning load. Peaktemperatures can be reduced by 5 to 7 deg.C

8. Aerated lightweight concrete blocks have thermal resistance 3 times better thancommon sand cement blocks 3w/m2K

9. Design Windows to block out direct sunlight. Let in the air and daylight. Diffuseddaylight gives more lumens per watt of heat produced than fluorescent lights.

10.External shading devices are more effective than internal blinds.11.Horizontal shading devices are generally more effective against the noon sun at east-

west orientations12.Vertical shading is only effective for south facing windows13.Egg-crate and pineapple-skin type shading devices is the most effective type of

window shading device and is suitable for all orientations


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