* One of them provides a direct comparison only for ‘wooden materials’; the other investigates only the energy costs of insulation.

† This is called the Energy Efficiency Commitment.

‡ In theory it reduces carbon emissions by 0.7 million tonnes – out of the 40 million our homes produce⁶⁷ This is regrettably no more than half the extra carbon emitted by the new buildings going up every year. But even this saving could be illusory: the government has no means of telling how much of it is lost through the rebound effect.⁶⁸