Sustainable Architecture Passive (3)

Lecture -03 Sustainable Architecture B.Arch. G.C.A.D. Asst. Prof. Lenin Sachdeva Asst. Prof. Parul Saini

Sustainable Architecture

Lecture -03 Passive Cooling Techniques

What is Passive cooling Passive Cooling Techniques

GATEWAY COLLEGE OF ARCHITECTURE AND DESIGN, SONIPAT HARYANA



PASSIVE COOLING CONCEPTS The first steps to achieve natural cooling in a building is to reduce unnecessary

thermal loads that enter it. Usually, there are two types of thermal loads i.e.

Exterior loads due to the climate and Interior loads due to people ,appliances, cooking , bathing , light etc. Proper zoning of different components and local ventilation of the major heat

sources can reduce the overall impact of internally generated heat loads .Depending on the weather , the heat gain in a building can occur in three major ways:

Penetration of direct beam of sunlight

Conduction of heat through wall , roofs

Infiltration of outside air



ORIENTATION OF BUILDING In countries like India , during the summers , maximum solar radiation is

interrupted by the roof [ horizontal surface ] followed by the east and west walls and then the south and north walls.

It is therefore desirable that the building is oriented with the longest walls facing north and south, so that only short face receives radiation from the east and west directions.

SHADING BY NEIGHBORING BUILDINGS The building in a cluster can be spaced such that they shade each other mutually. The amount and effectiveness of the shading , however , depends on the types of

building clusters. Building cluster can be classified into three basic types i.e. pavilions , streets and

courts . Pavilions are isolated building single or in clusters , surrounded by large open

spaces. Streets are long building blocks arranged in parallel by rows separated by actual

streets in open spaces. Courts are defined as open spaces surrounded by buildings on all sides.



SHADING BY VEGETATION Shading by trees and vegetation is a very effective method of cooling the ambient

hot air and for protecting the building from solar radiation. The solar radiation absorbed by the leaves is mainly utilized for photosynthesis

and evaporative heat losses. A part of the solar radiation is stored as heat by the fluids in the plants or trees.

SHADING BY OVERHANGS LOUVERS AND TEXTURED FACADES Few building element help in blocking direct entry of sunlight into building

envelope which is the most important strategy in passive cooling. Such elements may be integral part of the building or they may even be externally added . The devices that provide shading to an opening [door or window ] can be classified in to three types........

Movable opaque e.g. Roller blind , curtain ,etc; can be highly effective in reducing solar gain but eliminates view and impedes air movement.

Louvers , may be adjustable or fixed ,effect view and air movement to some degree , can also provide security .



Fixed overhangs .Easy to attain on single storey buildings with overhanging roof . Also gives rain protection to walls and openings .little or no effect on view and air movement.

MOVABLE BLINDS OR CURTAINS Movable blinds or curtains effectively block the transmission of solar radiation

through glazed windows , especially on the east and west walls. In hot and dry climates , when the ambient air is hotter than the room air , these devices also help to reduce the convective heat gain.

OVERHANGS AND LOUVERS Overhangs or louvers are utilized to block that part of the sky through which

the sun passes . This leaves the low angle view and entry of air unimpeded.



REFLECTING SURFACES If , the external surfaces of the building are painted with such colours that reflect

solar radiation [ in order to have minimum absorption ] , but the emission in the long wave region is high , then the heat flux transmitted into the building is reduced considerably.



THERMAL INSULATION

Use of insulation is a well –known and well practice concept used for energy conservation in building .In hot climatic conditions ,it should be ensured that the thermal mass is weakly coupled with external heat source [i.e. Solar radiation ],but strongly coupled with the interior in order to be able to absorb internal gain easily.



AIR CAVITIESAir cavities within walls or an attic space in the roof- ceiling combination reduces the solar heat gain factor [SHF].If it is possible to ventilate the air gap between the roof and the ceiling, then we could expect a further reduction of heat transfer .

Documents

Sustainable Architecture Passive (3)