I have a loft conversion I intend to re insulate.
Im thinking of removing the plasterboard to the pitched roof and using
50mm Kingspan or similar between the trusses leaving a air space between the tiles for ventilation. Then possibly battening by 25mm and using the thermofoil type material now available, such asOr I could use a further layer of 25mm Kingspan with no battens then the plasterboards.
Any thoughts?
Avoid multifoils
NT
/ snipped-for-privacy@care2.com
- show quoted text - Avoid multifoils
Links to where they're not mentioned at all....
Troll?
Jim K
Try and find a 'U' value for the stuff ...
There is a lot of scepticism about the foil insulation, so I would stick with the foam.
In principle, I think you might need to add more than this total of 75mm if you were looking to reach the U-values specified in the building regulations. Not that anyone will be inspecting it, of course (despite what anyone else might post), but for insulation their guidance makes a good rule of thumb.
It probably pays to put in as much insulation as the layout allows you to. Even though it costs a bit more, you'll get it back in comfort/heating bills and it will take broadly the same amount of work.
My next door neighbour has installed up to 150mm of PIR in some parts of his house (where it would take it without causing a problem) and his biggest complaint is that he struggles to turn his heating down far enough for comfort. Wish I had that problem......
In article , kev writes
The 50mm plan is eminently sensible, easy to achieve and could very will give you the insulation benefits you are seeking on their own.
If you are prepared to lose another 25mm in the room then add another
25mm in Kingspan/Celotex under the timbers and use long (PB) screws to fix new PB through into the timbers but don't expect it to be an easy ride getting the screws in the right places and not pulling through the PB at least occasionally.
ALL thermofoils are a total f'ckn joke and waste of time/money, avoid at all costs
It all depends how much surface area you have got, small attic room = small loss, large whole attic master suite with lots of exposed roof area and you would likely benefit from the extra 25mm of foam boards to keep it toasty.
/Try and find a 'U' value for the stuff ... /q
Nope not even in the wiki section impressively entitled-
'Insulation that doesn't insulate'
Oh well
Jim K
The troll whines but doesn't contribute anything. Its a _wiki._
NT
I've done this - with the benefit of roof retiling and a new breathable membrane.
The BCO allowed a 25mm gap between the tiles and the top of the celotex meaning I could use 75mm between the rafters. This year I will be adding
25mm under - this layer will also seal the gaps[1] and reduce cold bridging and act a vapour barrier for the wood's benefit. [1] Joints are foamed for the lower foot or so and along the wall plate.With a non breathable membrane it is harder - BCO would want a 50mm air gap plus ventilation to that gap top and bottom. With the breathable membrane, air wafting between the tile joints is deemed sufficient.
Aerogel is supposed to be teh next genuinely good thing - but it's not readily available to plebs yet - though I have heard of it being used on big jobs.
Just seem a building going up (new houses) and they are still using rockwool.
I've just done the attic rooms with 50mm Kingspan between the joists. Very impressed, seems to take relatively little heat to maintain a 20C temperature. Relative, that is, to the rest of the house, which does take some heating (Victorian terrace).
I don't see how that can work.
On hindsight, and if I planned to stay here more than 5 years, it's what I would have done
/ snipped-for-privacy@care2.com
- show quoted text - The troll whines but doesn't contribute anything. Its a _wiki._ /q
FFS again nige....
Where did I profess to know anything about shit insulation methods? to update out of date wiki articles that, oh yes the sore point:- you are heavily involved in maintaining/not (judging by the lengthy 'history' tabs on such pages)
Jim K
Just reinsulated my attic rooms. In one just used a form of multi foil, very thick and very strong, sealed with aluminium tape. Result
- pleasantly warm and comfortable. In second room, kingspan between joists and sealed thick multipoint. Result - very warm , I can't get over the difference it's made. I use this as a study and it's perfect.
I was going to say, in every loft room I have been in insulated or not, a fairly warm sunny h day has resulted in an oven in the loft room. I'd imagine air conditioning is the only real way out, as the room is just too close to the roof and has has been saide leaks can eleiminate any help from the insulation. Brian
I looked at it about a year ago and it is available but at high cost,
40quid a metre for a performance equivalent to about 30mm of celotex so approx 120quid a metre to get performance equiv to 100mm of PIR.It's cheap . . .
How thick is it (to match 30mm celotex)?
Although I would have thought the price difference for cavity walls would have pale into insignificance compared to the cost of bricks and bricklayer...
These are not cheap houses either - I've seen the marketing flyer and initial sale prices.
When I last did this[1] I followed a similar approach for the vaulted surfaces. Since the roof did not have a breathable underfelt, I added ventilation to the ridge (you could do this just by cutting away a strip of felt alone - although as I was renewing the ridge I also added some "weep" vents under the ridge tile on one side) and the eves.
I then stapled some thin battens so the side of each rafter to stop the insulation board moving to close up the ventilation gap, and filled the space with a 50mm thick foil faced board. This was cut with a slight interference fit to keep it snug and retained, and then expanding foam used to seal any gaps. That brought the insulation face flush with the underside of the rafters. I then added an addition 30mm board covering the insulation and the rafters, and finally screwed plasterboard (with
60mm dry lining screws) to the rafters through the extra insulation.The overall result met (and slightly exceeded the building regs requirements for a loft conversion at the time). It was a quite satisfactory result - the thermal performance far exceeded the rest of the house.
[1]
Can I ask a related topic about the floor under the loft conversion?
I have been thinking of similar to the above but appear to have a previous owner who carefully ventilated the area under the loft conversion above the first floor - what ventilation if any should that void be connected to?
It's approx 55% more effective than PIR foam board per unit thickness so
20mm of aerogel is equivalent to 30mm Celotex.At the time it appeared to only be available in 10mm thicknesses and so the 20mm would be 2 sheets thick.
We discussed it a little in the thread "How do they make a Part L door?" in Dec '13 and how it was being used to create minimally invasive insulation by adding 10mm to the inside of lossy council houses.
Look after the pennies etc, etc
Thanks - that's very interesting...
I also gather it is fire resistant (not only surviving but also containing fire). I assume though that it is not vapour proof so it may need to be combined with a vapour barrier in some applications.
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