Installing pir insulation between rafters before roof goes on

[Sniffer1977]

Hi all
Quick question , can pir insulation be installed between the rafters before roof covering goes on?
it will be open to the elements for a few days .

my thoughts are no , but wanted to check

thanks

 

[Notch7]

A bit more detail would be helpful

as you mentioned rafters, do you mean a tiled pitched roof?

why are you insulating at rafter level - is it a room in a roof conversion?

 

[^woody^]

Yes.

 

[Sniffer1977]

Yes.

thanks for the reply
Wouldn’t the pir be degraded if it rains solid for a couple of days?
I thought they had to be kept dry?

 

[Sniffer1977]

A bit more detail would be helpful

as you mentioned rafters, do you mean a tiled pitched roof?

why are you insulating at rafter level - is it a room in a roof conversion?

Thanks for the reply.
it is to be a cathedral ceiling so insulating between rafters then under .
Roof to be tiled .
its not me doing the work , I just thought roof has to be on (tiles) then insulate rafters from inside then another layer of insulation under rafter as I thought pir needs to be kept dry, rather than risked being rained on.
thanks

 

[Notch7]

Thanks for the reply.
it is to be a cathedral ceiling so insulating between rafters then under .
Roof to be tiled .
its not me doing the work , I just thought roof has to be on (tiles) then insulate rafters from inside then another layer of insulation under rafter as I thought pir needs to be kept dry, rather than risked being rained on.
thanks

PIR is closed cell foam so it won’t absorb moisture, although vapour can travel through it - unless foil faced

In reality building works just get wet if it rains, it’s impossible to prevent it - so your roofs timbers might get soaked, but once sealed in, the building dries out.

So it’s a vaulted ceiling - if its a cold roof then you can fit the insulation, put on tiles, then do vapour barrier - you might need insulation in between rafters and across the rafters internally.

 

[ajstoneservices]

You can fit the boards before the roof is under felt and batten. But why would you.

 

[^woody^]

thanks for the reply
Wouldn’t the pir be degraded if it rains solid for a couple of days?
I thought they had to be kept dry?

No. It would take months and months.

 

[noseall]

Hi all
Quick question , can pir insulation be installed between the rafters before roof covering goes on?
it will be open to the elements for a few days .

my thoughts are no , but wanted to check

thanks

Yes you can - but why?

 

[Sniffer1977]

You can fit the boards before the roof is under felt and batten. But why would you.

Apparently it’s easier , but it makes sense to me to do it from underneath when the roof is on

 

[Sniffer1977]

Yes you can - but why?

Apparently it’s easier , but it makes sense to me to do it from underneath when the roof is on

 

[noseall]

Apparently it’s easier , but it makes sense to me to do it from underneath when the roof is on

Is it a vaulted roof?

If so, then it easier. Only trouble is, the sparks or plumbers will be pulling it all out to do their first fix.