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Green WallsPosted by Kavi Jha at October 12. 2010
(Submitted by Ashwin Architects to Property World-Intelligence of the Indian Real Estate Professional magazine of United Business Media Group upon invitation to do so from the Bureau Chief Joseph Verghese)
Green walls are generally walls that are part of a building covered with vegetation. In most cases the vegetation is on the outside such as a creeper system with roots on the soil & with the chance to grow vertically. Studies have shown that there is a tendency for these walls to produce better cooling thus reducing our dependency on mechanical means.
(Using these concepts coupled with basic climatology techniques, we did an experiment where we tried to grow ivy type creepers on a west facing facade. Although we did not have any scientific methods to confirm the cooling effect, it was generally felt that the adjoining hall had cooled by atleast 3-4 degrees, even with direct sun rays. However, the creeper induced small cracks in the plastering which caused dampness on the inside wall.
We tried another experiment on a site where we used two wood supports on the sides of size about 10” wide & about 10' high with 10' space between the two wood posts. On either side of the wood, we used a wire mesh (chicken mesh) with intermediate supports which created a cavity of 10” width. We filled the entire cavity with mud & planted creepers. The basic idea was that such psuedo walls could be placed in front of the regular masonry walls for which we needed to provide thermal cooling. However, the setback was that all the mud eventually dissolved. With little bit of research, we found that many people used geotextiles in between to provide easily manageable layers of mud. But this eventually increased total wall width to three times the actual size that was perceived as a waste of space by many clients.
Hence, we realized that the ideal system would be to use a lightweight support structure for the plants thus reducing the overall thickness of the green wall & yet reap the benefits that a green wall system offers.
We used a similar technique in a residence where the roof was embedded with terra cota tiles with air gaps. This system provided us with a saving of almost 40% on cement consumption (for roof) & also reduced the steel quantity consumed by about 20%. This system ensured that the house stayed cool even during the harsh summers. Provisions were made for air-conditioners in this house but our clients informed us that they did not have to go in for AC's at all.
Although most people are aware of environmental issues, still the percentage of people willing to try out new techniques are limited. Hence we use climatology & building orientation to a great extent to provide natural light & ventilation thus reducing dependency on mechanical means of controlling temperatures. Other techniques we use are borewell recharging with roof water run-off, solar lights for the house, solar geysers, motion-detecting sensors for lights. In one case a client has been convinced to go in for a small windmill (that they are now available for homes though the cost is prohibitive). Provided the feasibility is positive, our client will shortly install the windmill.
Though I am doing quite a few commercial projects, I enjoy designing residences. You must already be having the basic details on greenwalls. Hence I am dispensing with definitions, etc., & providing a small write-up on our experiences. I have also indicated about other methods that we use for sustainability.
The issue of sustainability gets relegated to the second spot because the first question about construction is the cost. Hence, the initial expense is more when compared to a regular building and this difference becomes magnified in the unorganized construction sector.
In the residential sector it is even more difficult to recover the savings & sometimes the payback period may extend upto 7 years. However, in the office / commercial sector, the payback period is generally 3 years, the main culprit being the AC system. Today, the sector is using VRF AC systems that actually reduce the power consumption by about 25% though initial investment is higher by about 30%.
Though the buildings being registered with LEEDS & GRIHA are increasing so is the unorganized sector.
In today's recession, we do have clients who want to provide a gold-rated (LEEDS) buildings, however, market (tenants) is not in a position to support the higher rentals. Hence, it was decided to incorporate green concepts that would only increase the cost by a small percentage.