Solid Attic Insulation - Is there such thing.

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ryan-neil

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Hi,

Is there such a thing as solid attic insulation, like a foam board that can be cut and laid between the joists. My joists limit me to 200mm of insulation but i also want to lay down a floor on top of the joists for storage. Is is possible to get a solid type of insulation that doesnt compress like fibreglass.

Thanks
 
ryan-neil said:
Hi,

Is there such a thing as solid attic insulation, like a foam board that can be cut and laid between the joists. My joists limit me to 200mm of insulation but i also want to lay down a floor on top of the joists for storage. Is is possible to get a solid type of insulation that doesnt compress like fibreglass.

Thanks
Click to expand...

Kingspan do a polyurathene (don't know if that is spelt right) board that comes in 8 ft X 4ft that can be cut to size. It's has much better insulation values than other forms of insulation. It's a little bit more expensive but well worth the money.

Any builders suppliers will stock it.

Ruam
 
it's used everywhere in building - cavity insulation, between rafters/trusses in attic conversions - has a great u value and very easy to work with. it is very common at present.
 
The rigid board insulation isn't as good as fibreglass as it it is near impossible to get it to fit tight to the joists - and dont forget the joists should also be insulated.

Aeroboard (formerly Southern Chemicals) have a rigid board insulation that is fixed to the underside of ply - you simply screw it down to the tops of the joists. Mind you its not cheap but it gives you the benefit of having the entire area insulated combined with a solid decking for walking/storage
 
So would i be right in saying its still best to batten the joists and raise the floor to put in 300mm of fibreglass rathen than the solid stuff.
 
There's also Extruded Polystyrene - NOT EXPANDED Polystyrene (known colloquially as 'aerobord') - one such mfr is Dow, and it's available through providers nationwide - or contact the importers - Corcoran Chemicals or Insulation Distributors, both in Dublin.

It's a high performance board, and there are roof, wall and floor versions, of different densities.

The only issue, as someone pointed out, with rigid or semi-rigid products is fitting them effectively between joists - it's not that easy. Fibreglass I wouldn't touch with a barge pole, so how about Rockwool ? I used that, then cross-battened at 90 deg to the joists, with another 50mm rockwool layer between, and floored over that with OSB.

For really, really awkward spots, I used loose vermiculite and just poured it in - it doesn't blow around like poly bead.

NOTE: keep all styrene's away from electrical cables !! there is a potential issue with pvc insulation and polystyrene insulation.
 
I've used a product from Aerobord called Aerodorm. It's slightly compressible and therfore easy to squeeze in between joists. it's also very easy to work with. Wiring needs to enclosed in plastic conduit though (or kept away from it).
Regards
Fran
 
get an electrician to check the wiring in the attic,you shouldn't have insulation on top of cables.
 
Hi All,

Does anyone know if you can blow the insulated beads in between the joists like you would with the cavity wall? Are there any issues with this or has anyone done it?
 
the usual situation in the attic (if you want blow-in) is to blow in cellulous material, or rock fibre... eg PAROC..... polystyrene beads can cause a fire hazard as they react to electromagnetic fields around cables... unless your sure all your cable sare in ducts, i wouldnt use beads....
 
I had a similar issue on a new build. Put the normal fiberglass stuff between the joists & then X-Foil stuff over the joists. Its very thin has lots of strips of tinfoli & foam but does the same job as the fiberglass. Its a bit more expensive though. Then i put my flooring down over the xfoil on the runners in the attic.
 
that stuff doesnt have an agrement cert yet does it... (im assuming its the same as the super 10 iso stuff....)
 
ryan-neil said:
Hi,

Is there such a thing as solid attic insulation, like a foam board that can be cut and laid between the joists. My joists limit me to 200mm of insulation but i also want to lay down a floor on top of the joists for storage. Is is possible to get a solid type of insulation that doesnt compress like fibreglass.

Thanks
Click to expand...
Foam spray is a great choice if you have small areas that you need filled.
Instead of attempting to push loose insulation into these areas it can be sprayed in.The foam hardens and supplies insulating qualities to the areas where it has been applied
 
I bought pink foam boards from B&Q - I'll get the name tonight. Anyway, they have the same insulation value as 270mm of fibre. Basically, I laid 100m of fibre between the joists. Then I laid these board perpendicular to the joints. Then I laid the tongue&groove floor boards perpendular to the foam boards. The boards are approx 4ft by 2ft and cost 6 euro each. Very light and easy to manouver.
 
Perfect timing, I have insulated in between the joists with 150mm rockwool but I want to put down more insulation and yet keep some storage space. I will take a trip to B&Q. Thanks firefly.
 
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