Can I re-use these for my roof?

[ToughButterCup]

I have any number of these left over from the build. I'd like to stick them in my roof between the rafters.... but

 

 I have a dreadful feeling Mr @JSHarris will say ' No you can't ' . I think we've had this conversation before but for the life of me I can't find it.

Wasn't it the small gaps between the blocks that'll prove too hard to seal off?

 

Please tell me I can use them. It's such a huge waste not to....

 

 

[Construction Channel]

looks like a massive PITA to me,

 

if they were wide enough to span the gap, maybe, but as they don't you will have to wedge them together to try and get them to stay in, then you would ideally want to stick them all together with either LE foam or possibly some Pu glue, then technically you would want to foil tape all the joints.

 

possibly use them to finish the last pair if you run short but I definitely wouldn't start the job with them,

 

also FWIW i have heard that Celotex is going up again in the new year, so if you are going to order some i recommend ordering them before the weekend  

[Jeremy Harris]

+1 to the above, it would be a massive PITA to glue them all together into usable sizes with LE foam, then tape them.  If you really have got hundreds of them, then you could look at setting up a flat bench with some polythene sheet (LE foam doesn't stick well to polythene) and then perhaps make up some sheets that were the right size, it really comes down as to whether the cost of the LE foam, the tape, making up the bench to assembled flat sheets and your time works out cheaper than buying new stuff.

[Ferdinand]

Don't we need someone to test whether PIR goes up in steam?

[ToughButterCup]

If it's simply a pain I can stand that. 

Thanks folks. 

Ian 

[jamiehamy]

Of course you can use them (to answer the question posed)  - stick them together and couness hours later you'll be wondering if your time might not have been better spent actually doing something useful. Maybe I'm feeling a bit tender that I've worked for weeks without a single day off and having time to stick together pieces of insulation just to save a bit of waste is a positively luxurious thought!  If you've nothing else to do, I'd love to see pics of the patchwork quilt! 

[Triassic]

I’ve used offcuts for stuffing between rafters in the past. I started by stuffing the first one in, then used low expansion foam to put a bead on the joining face before stuffing the next one on, and so on.

 

Time consuming but satisfying. You often see loads of such offcuts in skips. You could probably fill the whole rafter space using freeby offcuts! Might be worth asking your local timber frame company what they do with theirs !

[ProDave]

Wasn't there a thread about putting these through a garden shredder to make your own "blown in" insulation?

[Onoff]

Excuse to build an insulated dog kennel?