Buildings have become more energy efficient thanks to construction practices that emerged in the last few decades, writes Jahnavi Sajip @NewYorkEngineers. Older buildings were designed assuming open windows, and heating systems were oversized as a result; on the other hand, modern construction practices focus on insulation and air-tightness to reduce heating and cooling loads.
However, there is still a key challenge to overcome: space heating and hot water systems are very dependent on fossil fuels, and energy efficiency can only reduce their carbon footprint up to a certain point.
Heating systems normally rely on boilers and furnaces fired by natural gas or heating oil. These account for about 60 per cent of the environmental footprint of buildings, according to the NYC Urban Green Council.
Many buildings have access to a steam supply from Con Edison, but this does not remove the environmental impact - steam production also depends on fossil fuels, and the emissions are simply happening somewhere else.