Kingspan seconds - foil or no foil

[RogerS]

Guess this is one for Mike. There's £7 + VAT a sheet difference in price and I need 77 sheets!

 

[9fingers]

Foil covering is claimed to add to the insulation value where the board faces onto an air gap. When the board is covered on both sides the foil adds no insulation value.
If you are relying on the board to give you a vapour barrier, I believe the foam to be closed cell but a layer of foil and well taped joints would give a certain vapour barrier but so would sheet polythene stapled on and a lot cheaper.
My 2p as an hammer chewer
Bob

 

[Malc2098]

I was lucky to get a pallet of seconds with no foil of an unusual size and thickness for my 'shop build for a really good saving.

I shall be putting them against OSB as the inner barrier. I will be sealing the edges with the WH2 tried and tested expanding foam delivered by a gun.

Not sure if I need an outer barrier. There will be an air gap.

 

[Woodster]

I need 77 sheets!

What are you building, a block of flats? :lol:

 

[RogerS]

I need 77 sheets!

What are you building, a block of flats? :lol:

smaller sheets. 220 m2

 

[Mike G]

Dunno Roger. I've never used or specified anything other than the foil faced jobbies.

 

[RogerS]

Went for no-foil in the end.

 

[meccarroll]

Went for no-foil in the end.

A thermos flask has silver foil and an air gap and takes ages to loose heat (excellent heat loss resistance) the foil on the sheets does the same thing.

Mark

 

[Tusses]

I've used tesco value kitchen foil and wall paper paste on polystyrene insulation before

I was also under the impression it has IR reflective properties

 

[RogerS]

Went for no-foil in the end.

A thermos flask has silver foil and an air gap and takes ages to loose heat (excellent heat loss resistance) the foil on the sheets does the same thing.

Mark

I think that the vacuum also plays a part.

Foil helps radiated heat loss, I believe, but the foil was much lower priced and I came to the conclusion that sticking in 100mm of Kingspan would be adequate. I know that if you look at the Kingspan site then they have an article that talks about improving the u-value if you use foil...but then it seems to me that they shoot themselves in the foot by saying '...sometimes as much as up to three times..'. Que ?


So many different types of insulation, so difficult to get definitive answers...in the end I think one does ones best within the economics. The only final thought that I have is possibly putting sheets of insulated plasterboard over the inside as the stud will still be in place and I'd prefer not to run the risk of 'seeing' them as it were as their thermal resistance will be different to the Kingspan filled gaps between them. Either that or shove a lot of the now surplus fibreglass insulation behind them. Or some strips of thinner Kingspan...

Slapping on insulated plasterboard is probably the simplest albeit not cheapest solution.

 

[RogerS]

Question....best practice says to use a foam gun to fill in the gaps.

But if the gaps are smaller than the nozzle (much smaller) then does one not bother ?

TIA

 

[9fingers]

Question....best practice says to use a foam gun to fill in the gaps.

But if the gaps are smaller than the nozzle (much smaller) then does one not bother ?

TIA

It is air flow that would otherwise bypass the insulation that that you want to stop. you can use aluminium tape perhaps or knife in the foam to the gap.

Bob

 

[Tusses]

could you stuff rockwool in the gaps to prevent cold spots, then tape over to make air tight?

 

[RogerS]

could you stuff rockwool in the gaps to prevent cold spots, then tape over to make air tight?

We're talking a couple of mm's here.

Bob..surely plasterboard on top achieves the same thing as tape?

 

[9fingers]

could you stuff rockwool in the gaps to prevent cold spots, then tape over to make air tight?

We're talking a couple of mm's here.

Bob..surely plasterboard on top achieves the same thing as tape?

As long as the insulation is perfectly flush with the frame everywhere then possibly no need for tape.

Bob

 

[RogerS]

Ah that makes sense, Bob...I'll go get some.