Suspended Floor Insulation Question

[TheHandyAndy]

Hi all,

I'm in need of some advice...

I'm have a suspended wooden floor of which the underneath is a car port and is outside, the upper side of the floor a bedroom. On my architects plans it states;

"Floor joists to receive 12.5mm plasterboard and skim finish to achieve 30 minutes fire resistance. Floors are to be provided with 100mm Rockwool or similar insulation to achieve sound insulation and additional 50mm kingspan kooltherm K3 insulation board over carport to achieve a minimum U-value of 0.22Wm2/K".

I'm nearly ready to do the flooring / carport roof, but do I put the Kingspan on the lowest part of the floor and put rockwool on top, just below the floorboards? Or vice-versa, or doesn't it really matter so long as the kingspan and rockwool are in there?

As I understand the above quote, I'll plasterboard and skim the carport roof, then from the floor above put in the Kingspan, then put rockwool on top, then floorboard the lot. Am I right?

 

[mointainwalker]

If you put the Kingspan underneath, its weight will not then be compressing the fibre wool which makes a very small difference to the insulation achieved.

So put it underneath.

 

[Blagard]

Hi all,
I'm nearly ready to do the flooring / carport roof, but do I put the Kingspan on the lowest part of the floor and put rockwool on top, just below the floorboards? Or vice-versa, or doesn't it really matter so long as the kingspan and rockwool are in there?

It doesn't really matter. Personally I would have the rockwool at the bottom because the kingspan has water vapour resistance and a vapour check on the inside of the thermal insulation is a better arrangement. I would expect your kingspan to be a snug/tight fit to the joists. - See different opinion to Mountainwalker, but neither is wrong!

 

[TheHandyAndy]

Thanks guys.

I figured that I could do it either way, if I put the kingspan at the top, I could put some battons along the joists to stop it compressing the rockwool.

I've also noticed that Kingspan is incredibly expensive, can I use Celotex instead? The thickness i.e. 50mm will be the same. What do you think?

 

[mointainwalker]

Two brand names for the same material - PIR. Your choice.

Not very professional of your architect to specify a brand, IMO, unless he had a specific reason to do so, and this is not obvious.

 

[TheHandyAndy]

Celotex it is then!

You've just saved me a few quid there!

Thanks Mointainwalker

 

[stuart45]

You can save even more buying seconds from a dealer in Wales.

 

[TheHandyAndy]

You can save even more buying seconds from a dealer in Wales.

Please tell me more?

 

[stuart45]

http://aandainsulationservices.com/
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