Attic Insulation

Matt406

Hi All,

I’m currently in the middle of a new build and I’m looking for suggestions on how I insulate the attic space. Ideally I’d like to insulate it with 400mm of fiber glass insulation. However my joists are 9” (225mm) and I’d like to be able to floor out the attic (for storage etc.) once complete. How should I raise the floor level so that I can accommodate 400mm of insulation without compressing it?

I’ve come across these online – “loft legs”…has anyone ever used them? Thanks.


http://www.loftleg.com/
http://www.amazon.co.uk/Loft-Flooring-175mm-Insulation-Spacer/dp/B00942ETKC

hexosan

I was at the ecological building airtightness course last week and they had a product that could be used to extend the joists to add extra insulation. Can't remember the name of the product but if you check the website or ring them I'm sure you'll find it.

Www.ecologicalbuildingsystems.com

Brave Harvey

I’ve come across these online – “loft legs”…has anyone ever used them? Thanks.

Hey these look a great, first i seen them, and not very expensive, thanks for the link, I'd imagine they'd be fine, put down a suitable board cut and fitted around any timbers in your roof...

Atlantic1

220mm of Moy Metac between your joists will give you a U Value of around 0.15 and you won't have to do any work to the joists.

Moy Metac (Thermal Conductivity 0.034) is vastly superior to Rockwool (Thermal Conductivity 0.044).

I've used it in my converted attic crawl space and it's great!

If you do raise the joist level and put in 400mm of Rockwool, you'll have a U Value of around 0.11.

What I would do is put the 220mm Metac between the joists and put 100mm of foil backed rigid insulation boards across the joists. And you can put attic flooring panels on top of them. It'd be more expensive but you'd have a top class job!

Brave Harvey

What I would do is put the 220mm Metac between the joists and put 100mm of foil backed rigid insulation boards across the joists. And you can put attic flooring panels on top of them. It'd be more expensive but you'd have a top class job!

You dont need foil backed in this position, I always thought that you keep your vapour barrier to the inside of your insulation? This option may have condensation issues.

220mm of Moy Metac between your joists will give you a U Value of around 0.15 and you won't have to do any work to the joists.

220mm of moy metac may give you a u-value of 0.15 but your not taking into account the ceiling joists, when calculating a u-value you must also factor in the timber joists and the thermal bridge. You may reach a u-value to meet Part L with that but a better job would be to have insulation to cross above the joists. The 400mm fibreglass insulation with the loft legs that the poster is looking at looks pretty good option.

Atlantic1

Brave Harvey wrote: »

You dont need foil backed in this position, I always thought that you keep your vapour barrier to the inside of your insulation? This option may have condensation issues.



220mm of moy metac may give you a u-value of 0.15 but your not taking into account the ceiling joists, when calculating a u-value you must also factor in the timber joists and the thermal bridge. You may reach a u-value to meet Part L with that but a better job would be to have insulation to cross above the joists. The 400mm fibreglass insulation with the loft legs that the poster is looking at looks pretty good option.

There's logic to what you say but Xtratherm Loft Walk-R (which is foil-backed) works pretty much exactly as I suggested. Page 7 here. And they don't highlight a potential moisture problem.

My neighbour is currently having his attic done. 100mm of Rockwool between the joists and the entire floor covered with Xtratherm Loft Walk-R.

Atlantic1

Matt406 wrote: »

Hi All,

I’m currently in the middle of a new build and I’m looking for suggestions on how I insulate the attic space. Ideally I’d like to insulate it with 400mm of fiber glass insulation. However my joists are 9” (225mm) and I’d like to be able to floor out the attic (for storage etc.) once complete. How should I raise the floor level so that I can accommodate 400mm of insulation without compressing it?

I’ve come across these online – “loft legs”…has anyone ever used them? Thanks.


http://www.loftleg.com/
http://www.amazon.co.uk/Loft-Flooring-175mm-Insulation-Spacer/dp/B00942ETKC

I saw a very similar product in B&Q last week. They pretty much do the same job. They may not be as sturdy but aren't as difficult to put in place I reckon. If you give them a call, they may have them at your nearest branch.

Atlantic1

Here they are........... http://reviews.diy.com/2191-en_gb/11837507/reviews.htm



And video of how to use them .......................... http://www.youtube.com/watch?v=Gp_-ImJOIBY

Atlantic1

€2.35 each in B&Q and 12 for €20.

Approx 210mm deep.