home insulation question

[timwilky]

So there is one hell of a draught blowing up from the sub floor through the hole where my mains electric enter the building and the hole where all the ring mains leave on their way round the house. Draught problem cured with an application of expanding foam spray. but whilst down there it is obvious just how cold it is.

My ground floor never feels really warm, despite the house having cavity wall insulation, newish double glazed doors and windows. So having experienced the sub floor cold, is it worth insulating between the ground floor joists?. and if so what with.

I guess my choice is really rockwool slabs or polystyrene. Do I need to leave any air gap. or can I just staple a reflective sheet to the underside of the joists? or should I combine both insulation and sheet?

any of the above, tbh, I would go with the option of kingspan between the joists, or yes you could use space foil or similar and staple to the underside of the joists, however this wont help the joists breath..

application of expanding foam spray

DO not get any of it on your hands, i had a run in with expanding foam last week, nothing would remove it, it took 5 days to wear off.

[timwilky]

just realised that the cheap option of polystyrene slabs would be a no no because of the fire risk. So I guess Celotex GA3000, 50mm.

TW - we get quite a draught blowing up through our lounge floor and have been looking at doing something about it as sash-windows have been restored and draught-proofed, doors draught-proofed, wall-cavities filled and roof properly insulated when loft-converstion was done a few years ago. Other than floor, all we can do is consider secondary glazing.

Neighbour had floor done. They took up the floorboards, rand chicken-wire over the top of the joists then down between them and used it to hold rockwool sheets in place. This allows ventillation but stops the draught. Floor feels warm now, and ventillation is good due to gas fire in the room.

Prob gonna do the same as a couple of floorboards need replacing anyway. Shouldn't be too expensive either.

Might try decorator's caulk between the boards, too, and between the boards and the skirting boards

[anna]

Originally Posted by beabert

DO not get any of it on your hands, i had a run in with expanding foam last week, nothing would remove it, it took 5 days to wear off.

Doesnt come out of clothing either, I have a pair of trousers that will testify to that

Originally Posted by anna

Doesnt come out of clothing either, I have a pair of trousers that will testify to that

Are they warmer now?

lol love it

Originally Posted by timwilky

just realised that the cheap option of polystyrene slabs would be a no no because of the fire risk. So I guess Celotex GA3000, 50mm.

Yes that will be fine, I believe its class 0 rated which is a good call.. tape the joints with duck tape not the silver tape as it isnt needed in an application like that.

Let me know how much you need and Ill see if I can get you it discount rate as celeotex is manufactured just down the road and we buy 1000s of m2.

Cheers

Alex