How to do loft insulation correctly
Discussion
Recently bought a 1930's semi which needs a complete refurb and has just got planning for a large extension to the side and rear.
The house is absolutely freezing, so looking for advice on what can be done to insulate the loft.
When the extension is done the hip end will be opened up when the new roof attaches to it, and at the same time we will replace all the existing roof tiles.
The current roof make up is: clay tiles, battens, 100mm rafters. No sarking or felt layer at all. The floor is 18mm chipboard over 100mm joists with patchy fibreglass insulation between them.
In the loft we have a brand new unvented cylinder, controls for the solar PV system, a new boiler going in sometime during the extension works, and a load of crap being stored up there. It will never be a habitable room.
Been buying up building materials on ebay and at my disposal I have loads of the following if they are of any use: TLX gold, 100mm earthwool, 50/100/140mm celotex.
What is the best way of insulating what I have, ideally at rafter level, without causing problems with interstitial condensation.
Want to get this right and not have to re-do things when we do the roof, so if its better to wait until then I am happy to do so.
Over to the PH experts for advice...
The house is absolutely freezing, so looking for advice on what can be done to insulate the loft.
When the extension is done the hip end will be opened up when the new roof attaches to it, and at the same time we will replace all the existing roof tiles.
The current roof make up is: clay tiles, battens, 100mm rafters. No sarking or felt layer at all. The floor is 18mm chipboard over 100mm joists with patchy fibreglass insulation between them.
In the loft we have a brand new unvented cylinder, controls for the solar PV system, a new boiler going in sometime during the extension works, and a load of crap being stored up there. It will never be a habitable room.
Been buying up building materials on ebay and at my disposal I have loads of the following if they are of any use: TLX gold, 100mm earthwool, 50/100/140mm celotex.
What is the best way of insulating what I have, ideally at rafter level, without causing problems with interstitial condensation.
Want to get this right and not have to re-do things when we do the roof, so if its better to wait until then I am happy to do so.
Over to the PH experts for advice...
Does the insulation not have to be 70% below and 30% between the rafters? I'm sure I read something like that, to prevent the risk of interstitial condensation.
If I did the 50 between 50 below, is it worth adding the tlx later when the old tiles come off? Also how does the ventilation gap work if I add the tlx later? Do I still need to maintain a 50mm gap or should the insulation then fully fill the rafters and be touching the tlx?
If I did the 50 between 50 below, is it worth adding the tlx later when the old tiles come off? Also how does the ventilation gap work if I add the tlx later? Do I still need to maintain a 50mm gap or should the insulation then fully fill the rafters and be touching the tlx?
What about when we replace the tiles? Surely then we will be adding some kind of membrane under them, if not the tlx, which will reduce the ventilation through the gaps in the tiles (not that there are any, they seem really tightly fitted together)?
As I said, the loft is only ever going to be used for storage and as a kind of plant room, housing the unvented cylinder, boiler, pv controller, and eventually the solar thermal gubbins and maybe an mrhv system.
I was thinking about lifting the flooring and redoing all the insulation between the joists, then laying another layer of 4x2 with insulation between them too, then boarding over the top. I do want to insulate at the rafters though, as the cylinder and boiler will be up there along with lots of pipework.
As I said, the loft is only ever going to be used for storage and as a kind of plant room, housing the unvented cylinder, boiler, pv controller, and eventually the solar thermal gubbins and maybe an mrhv system.
I was thinking about lifting the flooring and redoing all the insulation between the joists, then laying another layer of 4x2 with insulation between them too, then boarding over the top. I do want to insulate at the rafters though, as the cylinder and boiler will be up there along with lots of pipework.
Good to hear it made a noticeable difference. The house was painfully cold last winter. As soon as the heating goes off the temperature drops.
The reason I'm more interested in insulating at rafter level is because of the cylinder and boiler, I'd like to keep all that at a sensible , steady temperature. Also with the extension it has been drawn as a warm roof, and it would be easier to tie that in with an existing warm roof rather than some kind of hybrid setup.
The reason I'm more interested in insulating at rafter level is because of the cylinder and boiler, I'd like to keep all that at a sensible , steady temperature. Also with the extension it has been drawn as a warm roof, and it would be easier to tie that in with an existing warm roof rather than some kind of hybrid setup.
Edited by dazm on Thursday 26th October 09:59
If I do the 50 between 100 under will that be ok when I replace the roof tiles and add a membrane under them?
Also read somewhere about bringing it up to building regs standards if replacing more than 30% of your roof. Is that the case, and if so will the 50/100 celotex solution meet regs?
Also read somewhere about bringing it up to building regs standards if replacing more than 30% of your roof. Is that the case, and if so will the 50/100 celotex solution meet regs?
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