Underfloor insulated, still draughty

[ssray]

We have a 1930`s solid brick wall house that is on a hill, the front of the house is level with the road out front and the ground level of the garden is about 10ft below the back door, so we have a large void under the house.

I have fitted 100mm of solid urethane type insulation under the floor between the floor joists

We still have draughts, when I fitted laminate flooring in the living room I used silicone around the edges, I`m possibly going to do that in the other room but laminate is already down so it would be on top and possibly a bit messy

would I be able to put foil backed bubble stuff across the floor joists over the insulation, there is good air flow under the floor, would I be better using a breather type membrane and using some kind of expanding foam at the edges

I already have about 25sqm of the bubble foil stuff

Ta
Ray

 

[freddiemercurystwin]

Did you use expanding foam in the gaps between the insulation and the joists?

 

[ssray]

No, I cut everything so it was a tight`friction` fit,
would it be worth doing that then using my shiny bubble stuff?
Ta
Ray

 

[freddiemercurystwin]

Did you push your insulation hard up against the floor boards? How did you fix it in position, if you rely on friction alone you can find that your joists shrink a bit depending on the temperature and gaps can open up/the boards can fall out. So some kind of mechanical fixing is necessary and seal all joints with foam. You shouldn't need any additional membrane under the joists.

 

[geraldthehamster]

No, I cut everything so it was a tight`friction` fit,
would it be worth doing that then using my shiny bubble stuff?
Ta
Ray

Yes to foam, and you won't need shiny bubble stuff.

Cheers
Richard

 

[JohnD]

I do prefer mineral wool under a floor. It is easy to stuff into corners and edges to block draughts, with no precise cutting or foam needed.
(and is much cheaper and quicker than Celotex, Kingspan or similar).

The stuff made by Knauf, and sold under various own-brand names, is treated with Ecose and does not shed dust and fibres.

 

[drpepe]

I used celotex insulation up against the floorboards, then silver foil tape across every joist/celotex transitions and around the walls behind the skirting. It seemed to work nicely.

 

[ssray]

The stuff i used was £2 for a 10x 4 sheet, it's ex frozen food factory walls
I will foam everything and see from thertq
Ray