The evidence is pretty strong from the Federation of Master Builders, but in the same letter that I shall write to other noble Lords I will include any further evidence that can be produced to back up the evidential information that we have.
The noble Lord, Lord Krebs, asked about the scrapping of the zero-carbon element and where else carbon savings might come from. I reassure him that we are already starting to look at heating systems in existing homes. As noble Lords will probably be aware, heat accounts for around 45% of our energy consumption. More than 1.2 million new boilers are installed in our homes every year and we want to consider whether the time is right to raise standards upon boiler replacement, and what the benefits and risks are if we do.
I will also make a point that I wanted to raise slightly earlier in this debate about being overzealous in protecting homes. There is an issue which I know has cropped up in previous debates about overheating homes. There are concerns about making homes so energy efficient and airtight that they can contribute to health issues, so DCLG is looking at that. We need to create a balance between stimulating the building of new houses and making sure that they are user-friendly for people to live in.