GRIHA: Necessity, Not Luxury

For those in the know, an introduction would be redundant. But for those who aren’t, an introduction is a must – An introduction to GRIHA, or Green Rating for Integrated Habitat Assessment. It is, essentially,

• A point based voluntary scoring system to evaluate commercial, residential and institutional buildings on "green scale"


• Is based on Indian codes, standards and best practices


• Comprises an evaluation panel of eminent professionals
  

All right, so what’s the news? The news is that the Union Government of India has, in a landmark decision, made it mandatory for all new buildings of the Public Sector Undertakings and the government to seek new green rating norms in an effort to ensure energy efficiency and tackle climate change threats. Every government building, the law says, must get at least 3-star rating (on a scale of 1-5 stars) under the GRIHA scheme. And why not? The idea is to minimise demand for non-renewable resources and maximise utilization.

Take, for example, the Earth System & Environment Science Engineering Building, a research facility located in the Indian Institute of Technology Campus, Kanpur. The facility, as the name suggests, houses laboratories and other facilities for various disciplines of the environment sciences. The facility is nestled into the existing landscape. In siting the building, the natural course was left undisturbed. The architecture of the building has been designed around the existing vegetation, so as to not disturb the natural surroundings and fully grown.

The facility houses wet labs which are non-air-conditioned spaces on the ground floor and dry labs that are air-conditioned spaces on the first floor. Building design and envelope has been optimised through selection of appropriate wall and roof construction and through adoption of passive design measures after studying the sun path analysis to provide shading devices for windows and roof which would reduce energy demand to condition the spaces. This is probably the only existing building in India with a GRIHA rating of 5 stars, though there are several similar proposed projects, such as the Triburg Headquarters at Udyog Vihar in Gurgaon, Integrated Township in Kanyapur, Asansol, West Bengal, and the Office of Public Works Department, Nashik

Today, glass has an almost indispensable role to play in green architecture. Energy efficient glass is the need of the hour, given its unmatched features of optimum transparency that helps in day lighting of interiors, solar control & thermal insulation which cuts down the relative heat gain, and so on. To elaborate, glass can do the following wonders:

Day Lighting - The use of glass allows the penetration of adequate daylight and facilitates a reduction in power consumption.

Energy Efficiency - High performance glass helps control solar and thermal heat gain, thereby cutting down on air-conditioning expenses.

Recyclability – All architectural glass products are recyclable and qualify as “green” building material.

Recycled Content – The production of glass requires a minimum level of ‘cullet’ or broken glass in the Float Glass manufacturing process thereby by qualifying it as a material with high recycled content.

Acoustic Control – Certain types of architectural glass provide a high degree of acoustic comfort by obstructing the entry of sound from the exteriors of a building.

Blending Interiors with Exteriors – Facades made with reflective glass do not obstruct visibility from the inside.

Self Cleaning – The future belongs to environment friendly self-cleaning glass, a type of architectural glass that keeps itself clean and imparts a brilliant aesthetic effect to buildings.

Green architecture – GRIHA becoming law – Glass. Not just alliteration. A symphony, a necessity, a calling.

Self-cleaning glass

Self-cleaning glass is a specific type of glass with a surface which keeps itself free of dirt and grime through photocatalytic decomposition. A nanometer-scale coating of titanium dioxide on the outer surface of the glass introduces two mechanisms which give it the self-cleaning property. Harsh chemicals that are used to clean normal glass are usually washed off into the soil and contaminate it. The use of self cleaning glass eliminates this environmental hazard.

Dual Process

Self cleaning glass cleans itself in two stages. The first stage is called photo-catalysis which is the action of light on the surface of the glass to basically chomp away or eat the dirt on the surface. The next is a process known as hydrophilicity. This basically ensures that any water that falls on the surface forms sheets and washes away dirt uniformly. The glass spreads the water evenly over its surface, without forming droplets.

Working process of the Self Cleaning Glass


Self Cleaning Glass has a coating of titanium dioxide on its outer surface. Titanium dioxide is an inorganic pigment which is widely used in a several products: everything from sunscreen where it reflects away some of the sun’s UV rays through to toothpaste through to the whitener responsible for the white colour in white paint or even in paper.

Titanium dioxide is present as a very thin coating on the outside surface of the glass. It has a thickness of about 25mm. The action of sunlight on the titanium dioxide generates a species known as electrons and holes. These electrons and holes, along with a specific property of titanium dioxide migrate to the surface and start a process known as oxidation of any organic material which is present. Effectively, the titanium dioxide absorbs the UV component of sunlight and causes the degradation and break-down of any organic material, dust or debris which are on the surface of the glass - It converts them into carbon dioxide and water. One of the best features of this is that it works on the bottom of the dirt outwards and so loosens the dirt on the material coating by destroying the contact layer of the dirt and the glass.

Any rain water impacting the surface will form a very smooth sheet which washes down foreign particles uniformly. This happens through the action of sunlight on titanium that produces a surface which is highly hydrophilic, or water-loving. Water loves wetting the surface and the action of sunlight generates hydroxyl species on the surface effectively.

Everything that settles on self cleaning glass is washed down at the same rate, but this property primarily works on surfaces which have some form of slant. If the surface is perfectly horizontal then it would struggle because of a lack of gradient for the water to run off.
Only a small amount of sunlight is required to activate the coating, which ensures that self-cleaning property will function even on cloudy days. A simple rinse with water during dry spells will help keep the surface clean.

Performance

The performance of self-cleaning glass can vary depending on the environment and the location of the glass. The other factors in play are:

1. The type of dirt
2. The amount of dirt
3. Total exposure to light and rain
4. The incline of the installation

Optimum performance is obtained when the glass is installed in a vertical position, and receives maximum exposure to direct sunshine and rain.

Applications

Self cleaning glass is very effective in highly polluted areas. The areas of its application are as follows:
• Glazed facades, exterior shop fronts, display windows, overhead & atria glazing
• Conservatories, balconies, overhead glazing
• Windows & patio doors

Advantages

1. Less frequent cleaning – facade stays cleaner for longer
2. Much easier cleaning - less dirt and grime adheres to the glass
3. Save money - the cost of facade cleaning is reduced
4. Clear vision through the facade - even when it is raining
5. Neutrality and transparency is the same as that of normal glass
6. Less frequent use of detergents – saves the environment.