Silver Foil 'Bubble wrap' Insulation - Suspended Timber Floor

tekton23

Hi,

I am hoping this post might attract some attention from some insulation experts!

We are cold! We live in the ground floor of a Victorian house. The floor is timber above a cellar which we have access to. I want to insulate and as cheaply as possible. We can not lift the floorboards. I should say there is no insulation there at the moment meaning air just blows straight through our flat! When I sanded the floorboards I also sealed all the gaps between the boards, which has helped slightly.

I have started by wrapped the underside in silver foil bubblewrap insulation. My intention was to then add to this using rockwool. Both would be fixed tight up against each other against the floorboard. My question is if this is going to cause any issues such as condensation or otherwise. Am I doing this right?

Thanks,

Alex

tekton23

Should I be doing it the other way round? I.e. putting Rockwool up first tight against the floorboards, held in place with netting perhaps, then an air gap, then the silver foil to create a tidy ceiling and to act as a membrane.

I need to know if the bubblewrap insulation is breathable? If not I am going to be trapping moisture, it does not say on the packaging.

Alex

mart.vader

tekton23 wrote: »

Should I be doing it the other way round? I.e. putting Rockwool up first tight against the floorboards, held in place with netting perhaps, then an air gap, then the silver foil to create a tidy ceiling and to act as a membrane.

I need to know if the bubblewrap insulation is breathable? If not I am going to be trapping moisture, it does not say on the packaging.

Alex

I think you should be doing this, as you suggested, Rockwool first (or similar preferably non-itchy alternative) against the underside of the floorboards, then the silverfoil bubblewrap tacked or stapled onto the underside of the joists to prevent moisture going through, but your cellar must have adequate ventilation through air-bricks.

This is how I would do it, but there are arguments for putting the bubblewrap in first. i.e. allows air to circulate round the joists, to avoid possibility of rot.

Bubblewrap is not breathable, but, you could, instead, use Breathable roofing membrane, I have used this and there are different qualities and prices. but a roll of 50 metres by 1 metre should cost, say, between £30 and £65. (more than enough to do a very large room.)

Probably, someone on this forum will be along in a tick to confirm, which way is best.

tekton23

Hi,

Thanks, yes this does make sense and I can see now that I have made a mistake with the silver bubblewrap. It would be good to know how the Victorians used to insulate the floor?

Alex