Insulating living room floor

[julian924s]

Hi - first post and hoping for some advise please. Got a detached house built in the mid-90's that suffers from a cold living room. I'm wanting to better insulate the floor, I think a lot of this is caused by cold air coming up from the ground underneath. Got carpet and underlay down at the moment and upon pulling the carpet back the floor is plywood (or chipboard?) - I've no idea how thick it is but it is laid with no gaps between the boards and no noticeable drafts around the skirting boards.

I'm wondering what my options are and what I can do myself. I've read about removing the floor boards and laying loft insulation between the joists secured by garden netting laid in a zig zag fashion which sounds like a good idea. Or I'm sure I've read someone using 5mm fibreboard and then putting the underlay and carpet back down.

The main concern I have with removing the floor boards is they run right up to the wall so would I need to remove the skirting boards or damage them in the process of lifting the floorboards?

Thanks in advance - J.

 

[DAZB]

You have a two main options, either to insulate below the floor or above. The latter is easier but has an effect on the floor level and doorways, fireplaces and skirting etc could all be affected causing more work. The other option is to gain access under the floor by creating an access trap by which you can get under the floor. You may not know how much of a crawl space there is below your floor until you make an access trap so it may even be that it is not possible to get under but assuming you can then fitting rigid foil faced insulation such as Kingspan or Celotex 50mm thick between the joists is best. Cut them so they are a tight friction fit and leave them flush with the bottom of the floor joists (not up to the floorboarding). You can then apply silver foil tape to the joints to help keep them in place. It is not an easy job and will be dirty and cramped but should make all the difference.

 

[freddiemercurystwin]

Cut them so they are a tight friction fit and leave them flush with the bottom of the floor joists (not up to the floorboarding).

NO that is wrong, they should be flush with the top of the joists up to the underside of the boards, leaving a void will be prone to condensation.

 

[DAZB]

I was going on the principle of creating a void of air which, up against what I think from the info he gave is a T&G chipboarded floor, can help with the heat loss. Condensation should not be an issue as the floor above has underlay and carpet meaning a warm surface and below would have Kingspan so a moisture free zone is created between the joists but I am willing to be corrected if Kingspan say so.

 

[freddiemercurystwin]

Untitled

• freddiemercurystwin
• 12 Feb 2012
• 1

 

[julian924s]

Thanks for the replies, just a couple more questions!! Is it likely there would be a crawl space beneath? I just assumed there would be 1-2ft and then the ground underneath, but to be honest no idea why I think that. I'd thought to undertake this I would be removing each and every piece of floorboard to enable me to fit the insulation - but thinking about it the access trap / crawl space although being dirty and cramped would be the least disruptive - think I'll atleast make an attempt to remove one board and get a good look to see what I'm dealing with.

And as for actual insulation is the Kingspan or Celotex stuff the ones to go for and it a simple case off you get what you pay for?

Thanks - J.

 

[freddiemercurystwin]

You will have to lift a board or two to confirm the crawl space available if any. It can vary from 6" to a couple of foot or more.

Celotex or Kingspan are basically the same in terms of performance, you could use polystyrene which will need to be thicker or mineral wool suspended with chicken wire or similar which would need to be thicker still. The less you pay the thicker it needs to be.

You should investigate ebay and look for seconds or job lots left over from self builds or similar.