Practicalities of using PIR board in lofts

[garyo]

I'm still in two minds over using PIR board versus rockwool in my loft. I'm tempted to go for PIR board as it will maximise the usable space for ad-hoc storage.

I'm having second thoughts though, as the lof space will be 4.5M x 2M x 1M (high) - so I'm not sure its practical.

Given that electricity cables should be run over the top of insulation, and that the back of light fittings intrude into the loft space, how are PIR boards fitted? I'll probabyl have to chop mine up into fairly small bats to get them through the loft hatch at the end of the build - is this an issue, or do I just need to foil tape them back together once fitted?

Thanks

Gary

 

[SurreyRoofingEstimator]

I would think using the PIR boards will prove quite fiddly indeed, especially withe the lights.

I assume you have downlights as you specifically mention them, these you need to cover with a purpose made cap, these are actually quite bulky due to the amount of air gap you need over the back of the light fittings.

If you really want to go the PIR route you can get smaller boards than the normal 8' x 4' ones which may make it easier.

 

[garyo]

Yep - low energy downlighters due to only having a 2.2 metre ceiling height. So if I use PIR boards I'll have to cut a recess in the boards using my favorite kitchen knife, I guess.

I'd much prefer rockwool, but at 300mm versus 150mm, I'd lose quite a bit of storage space - well, that's to say, it could make the difference between 'quite usable' and 'unusable'

Unfortunately I'm tempted to fit 300mm of rockwool until Regs have signed the porch off, and then remove the top 150mm and board it out.

Gary

 

[noseall]

I'm having second thoughts though, as the lof space will be 4.5M x 2M x 1M (high) - so I'm not sure its practical.

1m high!

You avin a larf!!

Second thoughts.........you could be quite small for all i know.

But 1m high, at the highest point, ain't worth jack.

 

[garyo]

Yep, I know. The wife is convinced that as it'll be over the front door, it'll be handy for storing things like our inflatable touring canoe, which is currently cluttering up the conservatory.

I don't ever expect to get up there, other than popping my head in to grab something, and even getting in there to lay the insulation will be a royal pain!

Gary

 

[SurreyRoofingEstimator]

Have you just had a porch build and nothing else?

If this is the case why have you got to up your roof insulation (not that it isn't a good idea anyway.

Remember of course that the rockwool insulation can compress quite a lot as well.

The downlight caps will protrude a fair amount as well as they are the size of a reasonably sized flowerpot.

Maybe another option would be to use the 150mm Rockwool and then lay a multifoil type insulation over the top such as Superquilt 14 or Tri-Iso 10

 

[garyo]

Yep, it's a front extension/porch that I'm about to build, so at the moment there's no insulation at all.

Thanks for the pointer on the Superquilt - I'll take a look.

Gary