Insulation Slab vs Roll

[Mike.Hen]

I will insulating a suspended timber floor as part of a new extension build. I need 200mm wool for my u value of 0.18
What are the main advantages to using insulation slabs over loft roll other than the the loft roll is quite a bit cheaper. Thermally the only difference is 0.040 loft roll - 0.037 slab.

Will I notice any difference using the slab compared to the roll to justify the extra cost.

And yes I know I could PIR but looking to keep cost down and will being using celotex for the walls.

Thanks in advance

 

[tomfe]

Really just a different way to install them. Roll is easier if you have to cut anything down.
You'd normally use roll for floors, slabs are normally for walls.

 

[Mike.Hen]

Ok so I'm just as well going to for the roll as it works out cheaper for not much difference in performance.
Does anyone know if there is any difference between the Knauf Eko roll you get from B&Q which works out at a decent price and the Knauf earthwool 44?

Thanks

 

[John D v2.0]

I need 200mm wool for my u value of 0.18

Thermally the only difference is 0.040 loft roll - 0.037 slab.

earthwool 44?

Not sure about the difference, but
If you really need to get 0.18 to get it signed off, you should check your calculations. With 44 wool even without thermal bridging you'll only get 0.22 plus a little from the floor boards.

 

[Notch7]

you could try hybris actis

on a roll and cheaper than celotex.

http://www.insulation-actis.com/hybris-insulation.html

 

[Mike.Hen]

ive used the online calculator that shows i need 200mm.

https://www.rockwool.co.uk/technical-resources/tools/u-value-calculator/

 

[tomfe]

Does anyone know if there is any difference between the Knauf Eko roll you get from B&Q which works out at a decent price and the Knauf earthwool 44?

There is different grades of insulation, the cheaper stuff has a lot more recycled glass in it, virgin glass is nicer to work with.

The stuff Eon which was giving away for £1 a roll about 10 years ago had so much metal and other **** in it it was nasty to work with.

 

[JP_]

cost more, but I am putting in kingspan with slab on top. I find that slab cuts easier to size. But I only really have 100mm depth I can use. 50mm kingspan, 50mm slab on top.

 

[tomfe]

-

 

[Adam182]

If I could afford the extra for slab I would use it every time over roll, its just so much easier to work with.

I've used both the rockwool slab and the Earthwool Loft Roll 44 on my full renovation.

I noticed the stuff sold in places like BnQ, Homebase etc tended to have less per roll (it does actually state on the packaging so not in a shady way) it also tended to have a move DIY friendly name such as ''eco'' even though its basically the same stuff.

 

[John D v2.0]

ive used the online calculator that shows i need 200mm.

https://www.rockwool.co.uk/technical-resources/tools/u-value-calculator/

Got it, I've never understood what relevance the perimeter to area ratio has to a floor that has air movement underneath the insulation, but i know they take it into account so i can see you'll be ok the!