Harringay, Haringey - So Good they Spelt it Twice!
In between roof rafters insulation
I am in the process of having a new roof fitted. I am told I need a U value of 0.18. The rafters are 75mm deep. I have to leave a 25mm space between insulation and breathable membrane. This leave me with only 50mm space for insulation. Due to height restrictions I only want to use the minimum depth possible to achieve the required U value of 0.18 by means of a 50mm PIR board and a multi foil insulation. Any advice would be much appreciated.
Replies to This Discussion
-
Permalink Reply by Dan on
-
Such limitations on space to get anywhere near 0.18 look to be in the land of aerogels/VIPs. I'd suggest speaking to your/an architect to spec
-
-
Hi I tried to edit my last reply - but the changes didn't come through.
You have not mentioned any insulation below the rafters. This is where the gains are made if you must use PIR/PUR, etc. You'd be looking at >100mm below the rafters. There are a host of u value calculators on line to help you. As Robert says, you could also speak to your insulation manufacturer. Make sure you have any cold bridges sorted.
If you are restricted to 50mm, then as I say you should look at super-performance materials such as aerogels or VIPS to give you any chance of meeting 0.18.
-
Permalink Reply by Robert Pike on
-
I would recommend you give a specialist like Kingspan a call and ask to speak to someone in their technical department. http://www.kingspaninsulation.co.uk/applications/application/Roofs....
They are there to help and will be able to guide you better on suitable depths to meet U-Values. But if you are using an architect or builder they should be able to do this for you.
© 2024 Created by Hugh.
Powered by
