What’s good insulation?

Walls and roofs of a building should be built in a way that its indoor temperature is not disturbed and the extreme heat or cold outside does not intrude, say architects. But this basic wisdom is now on a market overdrive as a large number of insulation products have flooded the market. This market, expected to be worth Rs 3,550 crore ($670 million) by 2015, is booming at an unprecedented rate of 20 per cent a year, states a report by the Tata Strategy Management Group and FICCI released in October this year.

Poorly insulated buildings are difficult to air-condition and lead to high energy loss. The market is, therefore, abuzz with products that can be padded to the walls to improve buildings’ thermal insulation. These include hazardous materials like mineral wool, rock wool, vermiculite, foams, expanded polystyrene and extruded polystyrene. Market is also agog with technologies like vacuum and gas insulations. But this pushes for more air-conditioners when the need is to improve the design and make the buildings naturally comfortable.

The push mostly comes from energy regulations for buildings. The energy conservation building code of Bureau of Energy Efficiency (BEE) has prescribed the minimum thermal resistance, called R-value, for walls and roofs. "Although the R-values are much higher than anything you can get with traditional solutions, they make eminent sense for air conditioned buildings” says Kolkata- based architect Laurent Fournier. He finds fixed values justified only for big luxury air conditioned buildings.

High R-value, he says, does not mean high comfort. In non-air-conditioned buildings, techniques like shading and ventilation play a major role in improving a building’s comfort value.

But R-value has become the new mantra, with green rating agencies like LEED, GRIHA and BEE’s star rating vouching for higher insulation. India finds itself disadvantaged because imported, expensive and environmentally inappropriate material is being shoved in.

Worse, dependence on them has deflected the market’s attention from creative cooling designs. “For high-level insulation efficiency, inner walls must be separated from the exterior surface, which is exposed to weather conditions, just like a Thermos flask,” says Richa Joshi, architect planner.

Traditionally, in hot-dry and composite climates of north India, building had thick mud or stone walls with roofs of mud and grass sandwiched between timber and terracotta tiles to keep the heat out. These are still effective in the cool interiors of the havelis of Rajasthan. In hot and humid climates, architects make use of natural ventilation with light construction and high roof of organic material like thatch, keeth (interwoven coconut leaves) or plain terracotta tiles. These can be seen in the houses of Kerala and Tamil Nadu.

Thermal performance of modern buildings can be improved with intelligent architecture. Replacing conventional material like brick and concrete with autoclaved aerated concrete blocks, hollow blocks or other material with inherent higher R-values can also improve buildings’ insulation. Designs like filler slabs, double roof, cavity walls, composite walls and shadings also help insulate houses.

“Some of our traditional insulation systems like cavity wall may be low on R-value but have lesser embodied energy and are long-lasting compared to high- performance insulation products,” says Deependra Prasad, an architect based in Delhi.

Synthetic insulation products like glass wool and rockwool are carcinogens, says Fournier. “Thermocol (polystyrene) is worse as it is less stable than glass and other wools, and releases gases. I prefer to keep these out of my and my client’s houses,” he says. The US Department of Health and Human Services admits that enough research on health hazards from synthetic insulation products has not been done yet.

“Dependence on import and expensive technology transfer should be minimised,” says Delhi-based architect Ashok B Lall. “Efforts are required to reduce the use of resource-guzzling air-conditioners through good insulation, and not use insulation as an excuse to increase the numbers of air-conditioners,” he adds.