foam glass insulated founds ?

[scottishjohn]

anyone looked at this 

 looks like its better than insulated raft- or is it me 

Edited March 13, 2020 by scottishjohn

[Russell griffiths]

Seen the price of it. ?

[ToughButterCup]

Schaumglas, German innit? No bloody wonder it's expensive. 

[Jeremy Harris]

Unless you have a special need to use the higher compressive strength version of foam glass (for example as a thermal break if using strip foundations) then I can't see any real benefit.  It's far more expensive than EPS and has a slightly poorer λ in it's least dense form.  The one advantage it has is that it's available in a high enough compressive strength form to be used to take quite high loads, but the snag is that the high compressive strength version has a higher λ too, around 0.05 W/m.K. 

[scottishjohn]

was thinking of the foam glass chips --not the sheet

have messaged them and will see what they come back with -not seen any prices yet

 I suspect that my house will be built on solid rock -so may be that will already be better than mud etc should be dryier -- so maybe do not need that thick a layer 

[Jeremy Harris]

3 minutes ago, scottishjohn said:

was thinking of the foam glass chips --not the sheet

have messaged them and will see what they come back with -not seen any prices yet

 I suspect that my house will be built on solid rock -so may be that will already be better than mud etc should be dryier -- so maybe do not need that thick a layer 

 

 

The thickness only depends on the insulation level you're looking for, really.  Our slab has 300mm of EPS underneath it to get the U value down to around 0.1 W/m².K, and if we'd used foam glass we'd have needed a similar thickness, but it would have been a lot more expensive.

[scottishjohn]

2 minutes ago, Jeremy Harris said:

 

 

The thickness only depends on the insulation level you're looking for, really.  Our slab has 300mm of EPS underneath it to get the U value down to around 0.1 W/m².K, and if we'd used foam glass we'd have needed a similar thickness, but it would have been a lot more expensive.

the calculator they put on site --says different -which is why I,m waitng to speak to a real person -it say about 0.04 with compacted foam glass shards

we will see

[Jeremy Harris]

7 minutes ago, scottishjohn said:

the calculator they put on site --says different -which is why I,m waitng to speak to a real person -it say about 0.04 with compacted foam glass shards

we will see

 

The laws of physics dictate the thickness needed for a given U value, and the λ of foam glass is given on their website, so it's very easy to work out.  The high compressive strength stuff has a λ of 0.05 W/m.K, the lower compressive strength stuff has a λ of 0.036 W/m.K

 

Ignoring perimeter losses and the λ  of the concrete slab itself, to get a U value of, say, 0.15 W/m².K the  thickness needed would be about 235mm.  To get the U value down to a lower value, say 0.1 W/m².K would need a thickness of about 350mm (the actual U value will depend on the area/perimeter ratio, edge losses, slab thickness etc, so this is just a rough and ready estimate).

 

A layer of compacted glass shards 0.04m thick, if we assume the λ is around 0.04 W/m.K (which is probably optimistic), will give a U value of roughly 0.85 W/m².K, which is way over the limiting fabric values in building regs, which give a U value of 0.25 W/m².K