SBMS Posted August 31 Share Posted August 31 Anyone got any recommendations for a cost effective flat, fixed roof light for our flat roof that achieves 1.0 u value or lower? We need two and they are each 2800mm x1300mm. Link to comment Share on other sites More sharing options...
JohnMo Posted August 31 Share Posted August 31 Roof maker, do a Passivhaus approved one, it's got a U value of 1.0. don't pay for there upstands they are naff. Sit them on Compafoam CF200 upstands to get thermal bridge free install. Link to comment Share on other sites More sharing options...
SBMS Posted August 31 Author Share Posted August 31 3 hours ago, JohnMo said: Roof maker, do a Passivhaus approved one, it's got a U value of 1.0. don't pay for there upstands they are naff. Sit them on Compafoam CF200 upstands to get thermal bridge free install. Ah damn, now you’ve got me thinking of insulated up stands - never even realised this was a thing… Link to comment Share on other sites More sharing options...
JohnMo Posted August 31 Share Posted August 31 17 minutes ago, SBMS said: insulated up stands I gulped at the cost of Compafoam, but took joiner all of about 15 min to do two roof lights upstands. So overall good value. Link to comment Share on other sites More sharing options...
SBMS Posted August 31 Author Share Posted August 31 58 minutes ago, JohnMo said: I gulped at the cost of Compafoam, but took joiner all of about 15 min to do two roof lights upstands. So overall good value. Is the whole of the upstand made out of it? Have you got any pictures or details? cheers Link to comment Share on other sites More sharing options...
JohnMo Posted August 31 Share Posted August 31 Yes the whole upstand is made from pieces of Compafoam, it looks like polystyrene, is light, but like a stone for hardness. I used 75mm x 100mm, screwed through directly in to the roof structural timber, with a mastic in-between to seal. The roof light is then screwed directly to the Compafoam with mastic to seal. Sorry never got any photos. Link to comment Share on other sites More sharing options...
SBMS Posted August 31 Author Share Posted August 31 (edited) 10 minutes ago, JohnMo said: Yes the whole upstand is made from pieces of Compafoam, it looks like polystyrene, is light, but like a stone for hardness. I used 75mm x 100mm, screwed through directly in to the roof structural timber, with a mastic in-between to seal. The roof light is then screwed directly to the Compafoam with mastic to seal. Sorry never got any photos. Thanks @JohnMo got a video of it online. This looks like a great idea for our upstand. One problem is that we are doing warm roof construction so putting 165mm insulation on top. Compafoam looks like it’s max height is 150mm and I think regs state the upstanding needs to be 150 above the finish roof level. Would you do 150mm compafoam then a 165mm timber frame on top or two layers of compafoam to build a 315mm upstand? Edited August 31 by SBMS Link to comment Share on other sites More sharing options...
JohnMo Posted September 1 Share Posted September 1 I would build a wooden frame from the roof structure and around the aperture, to a height just below the top of insulation, so the roof insulation has something to butt up to also, use this framing to secure the Compafoam too. Then build up in two layers of Compafoam to get the correct height you need. Glue and screw the layers together to form the upstand Link to comment Share on other sites More sharing options...
SBMS Posted September 1 Author Share Posted September 1 Do you mean build a frame that’s 100mm away from the aperture around the aperture. And then on the ‘outside’ of this frame the PIR butts up to it and the inside the compacfoam? struggling to visualise what you mean Link to comment Share on other sites More sharing options...
JohnMo Posted September 1 Share Posted September 1 24 minutes ago, SBMS said: Do you mean build a frame that’s 100mm away from the aperture around the aperture. And then on the ‘outside’ of this frame the PIR butts up to it and the inside the compacfoam? struggling to visualise what you mean Does this make more sense? Link to comment Share on other sites More sharing options...
SBMS Posted September 1 Author Share Posted September 1 Would there not be thermal bridging that we are trying to avoid where the timber frame connects to the roof deck? is the roof light aperture to the left in your section diagram? Link to comment Share on other sites More sharing options...
SBMS Posted September 1 Author Share Posted September 1 1 hour ago, JohnMo said: Does this make more sense? Also - is the compacfoam effectively infilling the frame around the top of the aperture? Link to comment Share on other sites More sharing options...
JohnMo Posted September 1 Share Posted September 1 2 hours ago, SBMS said: Would there not be thermal bridging that we are trying to avoid where the timber frame connects to the roof deck? Making the wooden frame and having it shorter in height than insulation gets rid of any possible bridges. So if you have 200mm of insulation above the roof make the timber upstand about 170mm, the Compafoam then is 150mm plus 30mm, plus any boards on to of the insulation and your roof finish, so about 200mm high Compafoam. 2 hours ago, SBMS said: is the roof light aperture to the left in your section diagram? Yes Link to comment Share on other sites More sharing options...
SBMS Posted September 1 Author Share Posted September 1 15 minutes ago, JohnMo said: Making the wooden frame and having it shorter in height than insulation gets rid of any possible bridges. So if you have 200mm of insulation above the roof make the timber upstand about 170mm, the Compafoam then is 150mm plus 30mm, plus any boards on to of the insulation and your roof finish, so about 200mm high Compafoam. Yes @JohnMo thanks for this - am still a bit confused with the makeup.. Is it like the below (tried to show it from a few angles). So build a tinber frame around the aperture, then fill between studs with compafoam with levels as you mentioned? Link to comment Share on other sites More sharing options...
JohnMo Posted September 1 Share Posted September 1 Have done hopefully a clearer sketch Link to comment Share on other sites More sharing options...
SBMS Posted September 1 Author Share Posted September 1 18 minutes ago, JohnMo said: Have done hopefully a clearer sketch Thanks - and in between the studs of the timber upstands goes compafoam (my section view 1) or could I infill with the PIR? Link to comment Share on other sites More sharing options...
JohnMo Posted September 1 Share Posted September 1 41 minutes ago, SBMS said: Thanks - and in between the studs of the timber upstands goes compafoam (my section view 1) or could I infill with the PIR? No Compafoam goes above the wooden frame would have similar dimensions to the Compafoam upstand. The opening shown on my last sketch is the aperture for your skylight. So is showing the left and right of the aperture. You would line the aperture with 25mm PIR then plasterboard or what ever you want. So nothing like your drawings. Link to comment Share on other sites More sharing options...
SBMS Posted September 1 Author Share Posted September 1 I get you. Could I make the upstand out of two layers of 150mm compafoam instead of a timber frame? Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now