Retrofit Underfloor Insulation to Prevent Draughts in Ground Floor Information, help, tips and advice on cavity walls, ceilings and lofts etc....

[bobofernandez]

Hello Everyone,

I bought a house in May of last year and spent much time, effort and money updating and upgrading it. With the cold snap coming in though the drafts coming from under the floor at ground level are crazy.

I took up some of the floor boards to have a look and there is a lot of space down there, its between 1.5m and 1.7 m high depending on the area so it should be reasonable to work in. I have been considering my insulation options.

I have left over insulation from other jobs including, 1 roll SF19 multifoil, 1 roll of double sided foil buddle style, i roll of single sided buddle foil, and a host of XPS boards (enough to do about a third of the GF).

I am considering using the XPS boards and fitting them directly onto the beams (wording?!), do i need to use foil also to stop moisture?

Ill still need something else to complete the job though. I was thinking a kingspan/ecotherm rigid board, for budget Id like to stick with not having to use foiled boards, is that likely to cause issues going forward?

Advice appreciated.

[thedoctor]

If you are happy with the floor covering you have and with the space you have under the floor to work in, there should be no problemin cutting down the XPS to fit sugly in between each of the floor joists. They can then be "trapped" with treated battens screwed to the sides of the joists. There is no need for a vapour barrier necessarily but if you wanted to you could also cut the foil insulation and glue this to the underside of the XPS.