What are Green Buildings?

By
Er. Kaushal Kishore ,
Materials Engineer, Roorkee

INTRODUCTION:
A green building is that building which is constructed at a well planed location with proper design and sustainable materials. Fitted and painted with eco friendly materials. The building should gives to its occupants healthy and comfortable environment in all climates. It remains cool in summer, warm in winter, inside fully protected from rain, gives natural pollution free air and light through doors, windows and ventilators without any artificial means. For particular requirements it has solar, wind power and eco friendly electrical, mechanical etc. devices.

A green building should have all safety devices. It should be provided with potable water, having proper drainage, severage and rainwater harvesting system. The building should be surrounded with trees, plants and grass to provide natural greenery. Can the above building be possible when day by day the population in India is increasing at a very fast rate? The facts may be found from the following table.

Table: 1 Human population per sq.km of country area:

Country	Year
	1947	2009	2049
India	121	350	581
China	—	132	141
U.S.A.	—	34	49

With the increase in the population the house demand will also increase. For India it is of the top concern as by the year 2049 having the same country area 581 persons sharing recourses of one sq. Km. area against China 141 and USA only 49. From the present day crowd, it can be well imagine what will be the crowd condition of India in 2049. A drastic action is needed otherwise it will be too late to cope with this situation. There will be more slumps. By 2011 India will have 9.31 crore slump dwellers in which 31.63 lakhs people will be living in slumps in Delhi alone.

Some builders have a novel way to attract the client for the apartments they are going to build or already build. They gives big advertisement in green colour showing apartment surrounded by tall green trees. When you go to such site you will not found the trees of your dream. The other misleading advertisement is that the apartment has 70% open lush green area. The facts will be known when you calculate the actual open area for one house you will be going to live. See the following table:

Table 2: Actual open area shared by number of people:

Storey of building	Total houses	Covered area sq.ft.	Ground open area sq.ft.	Persons living in total apartment
1	24	36000	25200	96
5	120	180000	25200	480
10	240	360000	25200	960
15	360	540000	25200	1440

From the above table it can be seen that in a single storey apartment of 24 houses for 96 persons the open area is 25200 sq.ft., whereas for a 15 storey apartment of 360 houses for 1440 persons the open area is again same only 25200 sq.ft. Accordingly if a builder claim that his 15 storey apartment has 70% open area of covered area then the open area should be 378000 sq.ft. and not 25200 sq.ft.

Suppose per house there is one car, then a single storey apartment will have 24 cars and a 15 storey apartment will have 360 cars. In a 15 storey apartment where is the open space will be left for trees. To maintain our natural environment there must be one tree for each house. Accordingly in a 15 storey apartment having 360 houses there should be 360 tall trees. Have we such greenery in any of the apartment in our cities. How then they may be called green houses and claiming 70% lush green open area. The fact is we are living in congested places where we can never feel comfortable and enjoy the life of natural environment.

URBAN HEAT ISLAND MITIGATION
Urban areas have been found to have air temperature 2⁰C to 5⁰C warmer than the surrounding country side. This phenomenon known as the URBAN HEAT ISLAND EFFECT. There are number of ways one can fight the urban heat island at home and around the city.

1. Planting Trees: Trees are one of our most important allies in the fight against the urban heat island effect. Air temperatures directly under trees can be as much as 10⁰C cooler than temperature over unshaded blacktop. Trees can be sited stragically to shade roofs, pavement, walls, and other surfaces, keeping them cooler and reducing energy bills. Trees also provided a cooling effect through evapotranspiration. Other vegetation, including grass etc. also provides cooling effects, though not usually as significant as trees.

2. Green Roofs: Green roofs are roofs planted with grasses, flowers, or other vegetation. Like trees planted at ground level, the vegetation shades the surface, keeping it cooler. Reducing the urban heat island effect, isn’t the only benefit of green roofs- they can also be used to grow fresh local products in the city, and they significantly reduce storm water run off as well. Local birds will be attracted on the roof greenery and make their nest upon it.

3. Permeable Pavement: Many types of permeable pavement reduces the urban heat island effect in one or more ways. For example, many grid or block pavers incorporate grass or other ground covers, which help shade the surface of the pavement and increase local evapotranspiration. Porous pavements often have much lower total mass than asphalt or concrete, reducing the amount of heat they absorb and many permeable pavements are lighter colored than traditional pavement as well.

4. Building Walls: The walls of building should be painted with solar reflective paints.

5. Roofs: The roof of house remain expose to direct sun rays most of the day time. The traditional methods of keeping roof surface cool are lime terracing, mud phuska and brick bat coba treatment. These methods are not only time consuming, costly but also increases the dead load on roof. The new and very convenient method is to paint the roof surface white with solar reflective paint/coating.
Solar reflective coating is an acrylic based coating which provides weather proofing and heat insulation to the exposed roof. This can be used for coating RB, RCC roof top surface, asbestos cement roofing sheets, galvanized zinc sheets as well as aluminium sheets. With such coating temperature may be lower upto 10⁰C thus giving cooling comfort to the occupants of house and also reduces the load on Air Conditioner.

We are thankful to Sir Kaushal Kishore for publishing his unpublished research paper here on the website. This would be of great use to all the civil engineers who work are looking for information regarding Green Buildings .

If you have a query, you can ask a question here.