Question

To ask the Secretary of State for Energy and Climate Change, if he will estimate the average treatment cost to insulate (a) narrow cavity hard-to-treat walls, (b) uneven cavities in walls constructed of natural stone, (c) homes with defective or missing damp proof courses, (d) solid wall properties treatable with internal cladding and (e) solid wall properties treatable with external cladding.

The government's most recent assessment of the costs and benefits of energy efficiency measures are set out the Assessment of Impacts which was published 5 March 2014 alongside the Future of the Energy Company Obligation consultation, available here:

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/286926/The_Future_of_the_Energy_Company_Obligation_Assessment_of_Impacts.pdf .

For the purpose of this assessment, we assumed that the average installation cost for all Hard to Treat Cavity Wall Insulation measures was £1,296. We assumed that the installation cost for Internal and External Solid Wall Insulation (SWI) varies by property size, ranging from around £4,000 to £8,000 for Internal SWI and around £8,000 to £14,000 for External SWI.