Question to the Department for Business, Energy and Industrial Strategy:

To ask Her Majesty's Government, further to the Written Answer by Lord Callanan on 23 July (HL6670), what estimate they have made of how much less carbon dioxide would be emitted if boilers in all large houses were fitted with stored passive flue gas heat recovery technology (1) when such houses are built, or (2) when boilers in such houses are replaced.

Passive Flue Gas Heat Recovery System’s (PFGHR) with thermal storage can deliver total annual gas savings for heating hot water of around 30% for a typical domestic building. This is equivalent to a boiler efficiency improvement of around 5% versus a system without. These savings can vary significantly depending on the volume of the thermal store, space heating demand, usage patterns and property type.

Domestic hot water gas savings will typically be close to 20% for a new-build dwelling, and up to 35% for a larger existing property.