Floor Insulation

[NewToAllOfThis]

Looking at 160 - 170mm of insulation to put on top of Beam and Block and then finishing with 55 - 65mm of Screed, no underfloor heating.

 

The SAP has quoted 0.022 W/m2K

 

Looking for best value for money manufacturer / Supplier

 

I see there are Foil or non Foil coverings, what is the rule / benefits of each

 

What is the view of using seconds, does Building control usually visit between laying the insulation and having the Screed laid as looking at secondsandco.co.uk they state that insulation thickness can vary by 10mm. Also, are seconds acceptable on new builds, will there be any problems meeting building regs.

 

[A_L]

The U-value will depend on the insulation material, assuming PIR/PUR, and the exact area and shape of the floor, but looks reasonable.

 

Foil only has an insulating value when there is an airspace in front of it, it will also be destroyed by contact with screed, although you will have a polythene slip layer above it.

 

The other problem with seconds is that they may be bowed

 

Loss of 10mm should still be within the limits

[MikeGrahamT21]

You'll need the foil boards, taped with aluminium tape, so it acts as a VCL, and also stops the screed soaking in/leaking through. As @A_L has said, if you are putting a membrane above the insulation, this will be all you will need, and the board type doesn't matter, just go with a cheapest in the insulant type you choose.

 

Seconds could well be bowed, depends on which you are buying. I've bought loads of Kooltherm boards from seconds and co, and they're always perfect, you'd never know the difference, until you measure them, they're often a few mm different in thickness to what they should be. They can also be one thickness at one end and another at the other, so something to be aware of. Kooltherm boards come in a 0.018, but they obviously carry a price premium.

[ADLIan]

Second quality insulation would not be fit for use under the Regs. as it will not comply with the relevant BS, carry CE mark or be BBA approved. Not sure how well this is policed though. Also insulation may be branded as a  second for not being the right thickness but more seriously may also have failed other tests such as compressive strength or thermal performance.

[nod]

You will need to put a membrane below your insulation and attach it to your wall dpc 

It’s worth putting a slip membrane on the top also 

BC will want to see all this before the screed is laid

and should be very keen that everything is done right 

[Russell griffiths]

2 hours ago, MikeGrahamT21 said:

 

You'll need the foil boards, taped with aluminium tape, so it acts as a VCL,

 

No he won’t, if it’s laid over a block n beam floor he will have a damp proof membrane laid on the floor first, this will be taped to your perimeter damp proof course. 

 

Just like @nod picture 

 

did bc come out and look at yours @nod 

mine wasn’t interested, he had seen so much other stuff he told me to photograph it and send him a couple of pics. 

[nod]

6 minutes ago, Russell griffiths said:

No he won’t, if it’s laid over a block n beam floor he will have a damp proof membrane laid on the floor first, this will be taped to your perimeter damp proof course. 

 

Just like @nod picture 

 

did bc come out and look at yours @nod 

mine wasn’t interested, he had seen so much other stuff he told me to photograph it and send him a couple of pics. 

Yes he did 

Some do and some are happy with pictures 

Though any of us would have to be pretty stupid to cheat on this 

So pictures should be fine 

[MikeGrahamT21]

15 hours ago, Russell griffiths said:

No he won’t, if it’s laid over a block n beam floor he will have a damp proof membrane laid on the floor first, this will be taped to your perimeter damp proof course. 

 

Just like @nod picture 

 

did bc come out and look at yours @nod 

mine wasn’t interested, he had seen so much other stuff he told me to photograph it and send him a couple of pics. 

Surely it'd be better taping the joints in the PIR too to stop the concrete seeping down and negating the insulation though?

[PeterW]

3 minutes ago, MikeGrahamT21 said:

Surely it'd be better taping the joints in the PIR too to stop the concrete seeping down and negating the insulation though?

It is quicker and cheaper to lay a slip membrane and also the foil can be attacked by cement but that is dubious as no-one has ever proven the reaction occurs to the detriment of the insulation. 

[Russell griffiths]

4 hours ago, MikeGrahamT21 said:

Surely it'd be better taping the joints in the PIR too to stop the concrete seeping down and negating the insulation though?

You said to tape it all together to form a vcl, he will already have a Dpm under the insulation so doesn’t need two, it’s easier to use a separate thin plastic membrane on top of the insulation to stop the screed touching or falling into the gaps.