insulation types

JohnBoy

i had a big long post done up and then my laptop crashed, so here's the condensed version

sei reccomend 250mm blanket insulation in an attic

i'm going rennovating an attic room soon and will be insulating it, however 250mm is a lot of insulation to have on the two sloped surfaces of the walls/ceiling and would obviously encroach massivly on the room as there's another 50mm to be allowed for in ventilaton space between the felt and the insulation.

is aeroboard a viable option in this scenario for insulation? does aeroboard have a much higher insulation value than fiberglass wool for the same thickness?

or is aeroboad a major fire hazard.

this room will be walled/ceiled with T&G cladding, would we need plasterboard behind this from a fire safety perspective or is it ok to attach direct to timber?

patrido

t&g + aerobord with no plasterboard = fire risk

the fire risk should be taken seriously. use plasterboard underneath the timber cladding, and fill all the joints between the slabs to provide a good fire barrier.

also old style aerobord (unlike their new platinum products) are no better insulation wise than fibreglass.

if you want more insulation in less space use xtratherm xt/pr or kingspan tp10 between the rafters. you can also put insulation beneath the rafters... an insulation backed plasterboard like xtratherm xt/tl or kingspan tw56 is ideal.

i think the smallest version of these products is 25mm insulation + 12.5mm plasterboard. so the intrusion into your room is 37.5mm on each side.

an alternative is actis or other foil insulation. though you still need counter battens to provide an airspace on the room side of the insulation. opinions vary on foils and i wouldn't use it myself, but it is an option.

JohnBoy

cheers for that patrido, i shall do some reading up on those products.

is it only aeroboard that would pose the fire risk or should i be doing the entire room in plasterboard regardless of insulation type?

the reasoning behind the cladding was as much stylistically motivated as it was ease of DIY motivated

if the room is going to need to be slabbed out anyway don't know if we'd still do the cladding, we'd have to screw up battens through the plasterboard into the rafters i'm guessing to attach the cladding to?


hmmmmmm

patrido

yep, the fire barrier is to give you a half an hour to get out before the roof collapses, so you need it regardless of the type of insulation.

polyurethane/polyiso like kingspan/xtratherm insulation is also flammable and the fumes are toxic. rockwool/sheepswool/glasswool will not catch fire.

JohnBoy

hmmmmm

just read up on the kingspan products you mentioned and they do seem to fit the bill alright

dont suppose OSB has much of a fire barrier value

well i suppose all i can do is cost the job out and then see how the cladding would compare to getting a plasterer in to do a coat of skim. I'd do mud and tape on a wall happily enough but in angled corners on the roof i reckon i'd never get it right

i'm assuming the plasterer would be cheaper, anyone have a guide price on them?

the cladding can probably be done for around a euro per square foot including battens, based on B&Q pricing, and i'm assuming a plasterer is gonna be a hell of a lot less than that

CJhaughey

JohnBoy
You are right when it comes to taping and jointing on the vertical and even the horizontal as long as the joints are at 90º to each other it is easy.
It is very troublesome and hard on plaster to try and fill the angled horizontal joints to an acceptable finish on the angle upstairs.
My attic conversion was based on TGv and polythene vapour barrier and the insulation I used was blown cellulose, there is a guy called Francis Thoma and he is based in Kinsale 0863140004 is the number.
Me and mate did all the Taping and joining in a day it probably needs another 1.5 days to be ready to paint.
It is a way faster to do it this way than to try and plasterboard overhead and at an angle then fill with jointfiller and scrim tape.