Thursday, September 3, 2015

Ventilation at Homes




Though all the five Elements of Nature are essential for the life of all living being on earth, air is without dispute  the prime  among them. And within the house, we need proper ventilation for a salubrious atmosphere and healthy living.  For getting the welcome cool breeze inside the house, it is imperative that the air should be able to flow around the house freely.  It is a proven fact that on the windward side the air blows with some force or energy so that it not only enters the house but also absorbs and carries the heat to the outside on the leeward side of the building. To facilitate easy flow of air, we should have lots of open space in the way of its entry and some space on the other side for its easy exit as well. But the availability of more space in an urban context can be just about 10 feet and in a metropolitan city like Bangalore, even 5 feet will ensure quite a bit of natural ventilation.

A big house should mean that we have open space around the house, especially on the windward side. It will be better and beneficial to plan houses in such a way that the open space around the house becomes part of the house, and extend the house outward visually so that we can feel the house getting extended to the open space.

The sensible way to get this done is by taking the outside inside by bringing the open space inside and make it part and parcel of the house.  If we build from one end of the site to the other, covering more or less completely, then we are sure to feel cramped and ultimately suffer from lack of light and air.  As far as light is concerned, the natural light can be compensated to a certain extent, by artificial lighting, but not the natural ventilation. A fan just churns the same stale air. The air conditioners merely cool the air, recirculating a part of the used and exhaled air to reduce the load on the system.

It is the nature of air to blow from an area of higher pressure to that of lower pressure. On the windward side the air pressure is higher, on the leeward side the pressure is proportionately lower. Therefore to facilitate this we need to keep bigger windows on the windward side and even small windows will do on the leeward side to exhaust the warm and stale air.    

Wind will have positive pressure on the south and west during the summer monsoon months and similarly there will be negative air pressure on the north and east during this season. We feel the flow of air only when it passes by our body as a stream. But it flows rather slowly most of the time, even if we do not exactly feel it. The reason for this is the pressure differential between the two sides of a building, either adjacent or opposite sides. Even this slow movement of wind brings many air changes per hour and provide the much needed relief from heat.

Air  Circulation

Even when there is absolutely no air movement, or the condition which people normally call a 'still air ' conditioner, there certainly will be air exchanges happening. In this case there will be gaseous movement due to air diffusion, which is nothing but gaseous exchange from a higher level of concentration to lower level.  Generally carbon monoxide, carbon dioxide, body odour, cigarette smoke etc., which is being generated inside the house will be exchanged to the fresh air from outside, carrying in the much needed oxygen to the inside.  This exchange goes on in a passive way and even for this to happen we need sufficiently big windows to the outside.

Trees are always helpful in directing and cooling the breeze into the house. Trees with a large canopy not only cool the house, but also guide the breeze inside the house through the windows, likewise, shrubs and bushes could be strategically planted to guide useful breeze to the inside of the house and filter hot rays of sun.

Facing  the  Wind

Nowadays, it is a common occurrence to see the houses being constructed so close to each other that we cannot expect fresh air from our neighbour's  site.  One can depend only on the open space that is there around the house to allow fresh air to come inside. For this to happen, we need to keep more open space on the side from where we want the summer cool breeze to enter the house. This can be accomplished by keeping more open space on the south and west.  The south side open space is more useful because the sun will be at high angle on this side and it is easy to control the sun by providing minimum projections.  Even though we get a good breeze from the west too, because of the low angle of the sun from this direction in the afternoon, it is comparatively difficult to control sunlight penetrating the house.

However, we can keep large projections like portico and pergola covered gardens in the open space on the west and filter the sun light to a maximum possible extent, while allowing easy access to summer freeze.

We have very little control over the open spaces around only site.  For this specific reason, it is all the more important to leave sufficient open space around the building within our site since every inch of space cost multiples of hundreds of rupees in urban areas, we have to leave it where it really adds to the quality of living in the house and most importantly, open space has to be left taking into consideration the summer wind directions.

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Bannerghatta Road 


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