fernicarry
Member
- Messages
- 550
- Location
- Argyllshire
Hi All,
One of the jobs I've been meaning to get around to is insulating under the downstairs floors to help control drafts through the floorboards. I have decent access to the solum for about 2/3 of the main part of the house so plan to do the work from underneath. Realistically I'm not going to go to the trouble of lifting boards just to insulate.
Initially I bought a load of thermafleece with the intention of suspending it between the joists. We used this in our kitchen refurb but for that we had the floor up (was a chipboard floor so no historic fabric to lose) by hanging it on 'strawberry' nets slung across the joists. With hindsight this could probably have benefited from a bit more attention to detail as the UFH we subsequently put down does take a while to get going but the comfort levels are undoubtably better than before.
I also have a pallet load of Homatherm holtzflex wood fibre batts for use in the bathroom I'm redoing. This room has also been gutted with walls removed and boards lifted -- plaster was coming off in dinner-plate sized chunks and boards had been got at by woodworm -- so straightforward enough to cut to batts to size (but v. messy!) and insert into the stud work and between joists from inside the room.
It occurred to me that the holtzflex might be easier to fit under the ground floor by cutting pieces to a snug fit and then pushing up between the joists. The reality is that this has been a bit of a nightmare. One of the bigger problems is the joists having twisted over the years so that the gap at the bottom of the joist is smaller than at the top and the batts tend to just crumble apart if you bash them into place with any enthusiasm. Also a lot of the joist ends have been repaired with new pieces bolted on making spacing even more irregular. After two afternoon's work I'm about 1% done on the accessible part of the floor and rapidly losing enthusiasm.
So now I'm reconsidering my options. Maybe go back to the thermafleece but need a way to hold it firmly against the underside of the boards to prevent air gaps? The joist spacings are all over the place with a lot being wider a bit wider than the 400mm fleece but no where near as wide as the 600 so efficiently using the fleece will be a bit challenging. Or maybe cut the wood fibre batts under size to make it possible to maneuver them into position then fix battens to hold them up? Should I be worried about a 0.5 or 1cm gap around them, and if so best way to fill this gap?
Any suggestions on techniques for this or other materials I might want to try?
Btw solum is dry and well ventilated and joists in good condition so I don't believe I'm going to introduce any new problems by doing this. I'll also ensure I don't prevent air circulation up the inside of the external walls, in fact I'm digging out a lot of debris from the gap as I go along.
Cheers, Alan
One of the jobs I've been meaning to get around to is insulating under the downstairs floors to help control drafts through the floorboards. I have decent access to the solum for about 2/3 of the main part of the house so plan to do the work from underneath. Realistically I'm not going to go to the trouble of lifting boards just to insulate.
Initially I bought a load of thermafleece with the intention of suspending it between the joists. We used this in our kitchen refurb but for that we had the floor up (was a chipboard floor so no historic fabric to lose) by hanging it on 'strawberry' nets slung across the joists. With hindsight this could probably have benefited from a bit more attention to detail as the UFH we subsequently put down does take a while to get going but the comfort levels are undoubtably better than before.
I also have a pallet load of Homatherm holtzflex wood fibre batts for use in the bathroom I'm redoing. This room has also been gutted with walls removed and boards lifted -- plaster was coming off in dinner-plate sized chunks and boards had been got at by woodworm -- so straightforward enough to cut to batts to size (but v. messy!) and insert into the stud work and between joists from inside the room.
It occurred to me that the holtzflex might be easier to fit under the ground floor by cutting pieces to a snug fit and then pushing up between the joists. The reality is that this has been a bit of a nightmare. One of the bigger problems is the joists having twisted over the years so that the gap at the bottom of the joist is smaller than at the top and the batts tend to just crumble apart if you bash them into place with any enthusiasm. Also a lot of the joist ends have been repaired with new pieces bolted on making spacing even more irregular. After two afternoon's work I'm about 1% done on the accessible part of the floor and rapidly losing enthusiasm.
So now I'm reconsidering my options. Maybe go back to the thermafleece but need a way to hold it firmly against the underside of the boards to prevent air gaps? The joist spacings are all over the place with a lot being wider a bit wider than the 400mm fleece but no where near as wide as the 600 so efficiently using the fleece will be a bit challenging. Or maybe cut the wood fibre batts under size to make it possible to maneuver them into position then fix battens to hold them up? Should I be worried about a 0.5 or 1cm gap around them, and if so best way to fill this gap?
Any suggestions on techniques for this or other materials I might want to try?
Btw solum is dry and well ventilated and joists in good condition so I don't believe I'm going to introduce any new problems by doing this. I'll also ensure I don't prevent air circulation up the inside of the external walls, in fact I'm digging out a lot of debris from the gap as I go along.
Cheers, Alan