PIR under floor insulation around many pipes and obstacles

[BeeDeeVV]

We’re having a very small utility room built. We’ve been project managing it, bringing in different trades. There are a couple of things I'm doing (or trying too) which includes the joists and flooring.

I’m putting PIR between the joists, but I’m really not sure what to do between the first pair which have loads of pipes and cables, per the photo below.

My thoughts were either, put a few big blocks of PIR and then huge amounts of spray foam, or just use rockwool for that part?

Would it be an issue using the the rockwool which has a much lower u value for that small part?



Yes, our meter boxes are inside the extension, this had been run past the utility providers, and we had to get them to do a small amount of work on the gas, replacing plastic with metal for the pipes would now be internal.

[reggie747]

By the looks of it, you'll be building some kind of housing/cupboard around the boiler area on that wall so rock wool in the last joist gap shouldn't make any noticeable difference to it presenting a cold spot.

[hidetheelephants]

Spray foam could be a pain in the bks if access is ever needed. I'd try rockwool batts or PIR cut to go around the pipes and then stuff loose rockwool in the gaps.

[OutInTheShed]

You should take care insulating around any cables which might carry serious current.
Cables need to lose heat!

I'd just use rockwool where PIR is too awkward, the floor void probably isn't that cold and heat loss downwards through a fairly small area of rockwool is unlikely to dominate the losses from the room.

[BeeDeeVV]

Thanks all, rockwool sounds like the winner. Easiest to install and remove if required.

[Andeh1]

Yep, as said... Careful not to insulate cables, but otherwise just loose pack rockwool throughout.

[SoliD]

As above rockwool for such a small and potentially something that will need to come up in future, and look to put a nice airtight membrane over the top to stop any draughts.