Reuse ICF EPS for cold roof insulation

[Dunmow]

I have used isotex ICF to build the walls of my new build. I have quite a lot of EPS insulation blocks left as surplus (taken out of ICF blocks that were used for internal strucutral walls) and wondering if I can make use of them.

Can I use them for insulation in my cold roof, ie above the ceiling, below the trusses. The roof areas is too small to use as loft storage so dont mind if it is totally filled. I was thinking perhaps a super foil sheet or quilt and the lay out out all of the EPS blocks, 1 or 2 layers high. There may be some gaps.

 

Would this work as insulation? Or could it be used in addition to some other insulation such as super foil and glass wool? Do I need to tape up gaps? Is there anything else I need to take into consideration?

 

Thanks

[willbish]

I would guess that the offcuts you have are all quite small in size and so probably wouldn't work well internally.

 

I buried all my ICF offcuts against an area of the house below ground. As it's not the main insulation it didn't matter if it wasn't complete or perfect but the extra 200mm should help improve the performance a little in that area.

 

 

 

 

[Iceverge]

I've done this with a few bits of PIR I had hanging about. I just chucked them flat on top of our blown cellulose insulation. 

 

I do like @willbish idea aswell. 

 

No point in binning perfectly good insulation. 

 

 

 

 

[A_L]

1 hour ago, Iceverge said:

I've done this with a few bits of PIR I had hanging about

 

PIR, particularly if it has foil layers is virtually a vapour barrier. I would check the underside of the sheets for condensation, particularly if above toilet/kitchen. Probably O.K. if you have a formal vapour barrier but maybe not if you have a 'breathing' construction, I would check carefully. 

[Iceverge]

I had a look about 2 weeks ago. No condensation. 

 

Did a pretty thorough job on the airtightness layer however. 0.31 ach50. 

 

The pieces are about 500x500 just thrown on top of 400mm cellulose. 

 

Out of interest we had some extremely skeptical people on the build when I insisted on completely sealing the roofing membrane to the external plaster and taping all joints too. The cold roof space above the insulation is effectively sealed, depending only on the permeability of the Tyvek Supro for moisture control. 

 

We battened and counter battened and vented over the membrane. I must have been told 50 times that your roof will rot. Roofers were insisting a gale blowing through the rafters was the only way. 

 

On inspection the timbers were bone dry. No trace of mold or condensation anywhere. 

[Dunmow]

Thanks for your reply. The suggestion of burying insulation below ground would have been perfect but we have already filled in the ground around the foundations.

 

The blocks of insulation are quite large, though not solid throughout, more like an "E" shape. The back of the E is 500m, the top 350mm, the two gaps are 50mm wide and 150mm deep (similar to the sketch below - though this just shows the back of the E, not the legs). One room is currently stacked high to the ceiling with the insulation and I would really rather use them than throw them. Any other suggestions?

 

[Iceverge]

"Store" them in your loft while you think about what to do. They won't do any harm.  I'd line them up loose on top of any quilt insulation. 

[Gus Potter]

If you have a lot then you could flog them.

 

Neat SE / geotechnic trick is to use EPS blocks outside a retaining wall. This reduces the earth pressure on the wall in cases and can result in significant savings.

 

It's a long storey but if there is any interest?