Warm Roof Insulation

[Mulberry View]

My Architect specified 120mm PIR insulation for our Warm Roof (Standing Seam VM Zinc). I want to beef the insulation levels up to 200mm. I cannot rely on my Architect for support here.

 

I have a small (10sqm roughly) section of flat roof as part of the scheme where I cannot accommodate 200mm so I need a way to achieve an acceptable u-value compared to the 200mm on the rest of the scheme, but in a thinner build-up (the thinner the better). Any suggestions of ways I can do this would be greatly appreciated. Someone suggested 'Superquilt' as the VCL?

 

I'm poor at understanding u-values, so would appreciate some guidance on this.

[joe90]

I believe PIR insulation is not too good at sound insulation and metal roofing can be noisy, that would be my worry.

31 minutes ago, Mulberry View said:

I cannot rely on my Architect for support here.

Then sack him and find one that works for you!!!

Edited June 17, 2024 by joe90

[Mulberry View]

6 minutes ago, joe90 said:

I believe PIR insulation is not too good at sound insulation and metal roofing can be noisy, that would be my worry.

Then sack him and find one that works for you!!!

 

What's the alternative to PIR for this application?

 

As for the Architect, she sacked herself. She got paid then said she wants no more to do with the project. Getting another to pick up where someone else has left off is hard! Especially now we're in build and against a timeline.

[AppleDown]

Hybrid roof buildup hasn't had the best rep on here, but to my understanding if you do it properly and get a professional to look at the condensation risk it could be a way forward. So less PIR on the 'external' portion, and then add back in between the joists.

[nod]

As Joe has already stated Pir will amplify sound I would use Woolf batts Then muti foil taped Then counter baton and insulated plasterboard to deal with any condensation I’ve done this on numerous projects Bombproof 

[Mulberry View]

2 hours ago, nod said:

As Joe has already stated Pir will amplify sound I would use Woolf batts Then muti foil taped Then counter baton and insulated plasterboard to deal with any condensation I’ve done this on numerous projects Bombproof 

 

For a warm roof?

[Mr Blobby]

You need to talk to your zinc roof installers to agree the roof buildup. 

The federation of traditional metal roofing contractors has a guide, so warm roof is like this:

 

As others have said, you can put some rockwool between the rafters to increase insulation.  That's what I would do beacuse it would reduce noise but as others have said this becomes a hybrid roof and then you need to be sure of your condensation analysis.

 

We were in your position last year and we decided to scrap the warm roof and then go cold ventilated roof (with warm loft space) so we could put more insulation between the rafters and then pir under that. 

 

We changed the ply for sarking board, and that was a good idea.  No need to worry about it getting wet during construction and cost is not too much more.

 

 

 

 

 

[Mulberry View]

9 hours ago, Mr Blobby said:

You need to talk to your zinc roof installers to agree the roof buildup. 

The federation of traditional metal roofing contractors has a guide, so warm roof is like this:

 

As others have said, you can put some rockwool between the rafters to increase insulation.  That's what I would do beacuse it would reduce noise but as others have said this becomes a hybrid roof and then you need to be sure of your condensation analysis.

 

We were in your position last year and we decided to scrap the warm roof and then go cold ventilated roof (with warm loft space) so we could put more insulation between the rafters and then pir under that. 

 

We changed the ply for sarking board, and that was a good idea.  No need to worry about it getting wet during construction and cost is not too much more.

 

 

 

 

 

 

The Zinc contractor has agreed a build up for the 2 roof areas that he is applying Zinc to. This is a third 'flat roof' section that will not be Zinc'd, but is partly implicated in the main roof, so it's hard to tell if its even his problem.

 

I don't think we can do anything but a warm roof with our design, but the rain noise is a bit of a worry. Is there a better material that could be used perhaps under or over the PIR layer to dampen the noise?