Insulation Question

[nelliedee]

I have been offered 50mm Dense sound/heat insulation slabs (green fibre type). My question is whether or not I can use them on our block built extension?
They have been removed from a recording studio.
Any help much appreciated
Gel

 

[^woody^]

They are unlikely to have the water resistant coatings for use within a cavity wall.

Either way, 50mm is not enough for thermal insulation - it will need to be 100mm of this stuff.

 

[nelliedee]

Hi
Its not a cavity wall its solid breezeblock so will these do for roof insulation maybe if not on the walls?
I only ask as I have been offered a large quantity and it seems a shame to turn them down if i could use them somewhere. Maybe between the stud partition walls?

 

[^woody^]

Assuming this is rockwool, or very similar, then you will need 250mm of it in the roof. But if it is heavier than normal rockwool quilt, or not as flexible, then it may cause problems.

Yo e can use it in the stud walls

 

[nelliedee]

thanks woody.
The plans ask for 50mm celotex or equivilant for the walls. I am picking these slabs up this afternoon. Could slabs be used on the external walls between battens before the plasterboard goes on? or does the insulation for the external walls need the vapour sided insulation?
by external walls I mean the perimeter walls that need insulating
Thanks for your patience
Gel

 

[freddiemercurystwin]

In any case it may depend on the inspector, he may well want some proof as to what it is before he allows it.

 

[noseall]

In any case it may depend on the inspector, he may well want some proof as to what it is before he allows it.

'tis true. A license (BBA approved) is a good start.

I actually wrote the above sentence as "A bba license" and it looked like a seventies pop group.

 

[^woody^]

You will [probably] need 100mm of this free insulation to be equal to 50mm of celotex. Yes you can use it, as long as you then add a vapour check (polythene) or use vapour check plasterboard.

But losing the extra 50mm of space off the room, may not be worth the actual cost saving.

 

[alittlerespect]

You will probably find out as time passes by that the insulation material does not have the correct level of moisture resistance, and condensation forming between the external wall and the insulation will cause the insulation material to become saturated, both reducing its thermal performance and leaving you with the problem of replacing the material!

Best bet - Get the insulation checked out before you install - contact your local Building Control and they should be able to advise on a suitable agency who can do the testing for you.

Regards

 

[freddiemercurystwin]

contact your local Building Control and they should be able to advise on a suitable agency who can do the testing for you.

That'd cost about 10x the cost of buying the right insulation in the first place!

 

[nelliedee]

Best bet - Get the insulation checked out before you install - contact your local Building Control and they should be able to advise on a suitable agency who can do the testing for you.

My Building inspector will advise us on his next visit



Ok I have collected the slabs and they are the ones I have bought before from Wickes that I used to insulate the loft, itchy stuff. I think they will be ok to use in the stud partition walls that divide new rooms but not so good to insulate the blocks before plastering. Probably can use inbetween the 1st floor joists aswell and if we can use it in these places then it will have done us a good turn
Gel