Roof lights + build control = flustrating problem

[bookworm2006]

I've recently had an extension built and am in the process of trying to get a completion certificate. During the final inspection by building control I was told that I would need to provide documentary evidence showing that all the glazing installed has a thermal transmittance U value of 1.8 or better. I was a bit surprised by this as the french doors, windows and roof lights used all come from reputable sources like Builders Depot.
I have managed to track down the manufacturer of the french doors and windows and they have been nice enough to fax me the relavent techincal approval documents from the BBA. I have contacted the manufacturer of the 2 roof lights I've had installed and they don't seem to be as well organised. They have given me the mobile number of their sales man but all I keep on getting is his voicemail. The roof lights are cox dome trade models 1050 mm sq. I've looked up the company who make cox domes on the internet and they seem legit.
I am a bit surprised that building control have asked me to jump through these hoops as I find it hard to imagine that everyone who is gettting extensions built is having to call up the glazing maufacturers to get 18 page technical reports faxed to them. Is this this normal or is my building control department going over the top?

 

[freddiemercurystwin]

Its perfectly normal these days for an inspector to insist on you proving that your windows comply with the regs. Whilst Coxdome trade windows achieve a Uvalue of 2.2 its questionable whether they achieve 1.8 which is now required when installing a window in a new extension under the latest regs. Ring them and speak to their technical department. Unfortunately the responsibility was on you to make sure the windows complied before buying them. If it turns out they don't achieve 1.8 and the inspector is a real stickler you'll have to try and persuade the inspector to let it pass somehow, maybe by offering to add extra insulation elsewhere or similar to compensate. Were drawings produced/who proposed Coxdomes?

 

[bookworm2006]

The units are the triple skinned version of the trade model and were purchased my builder, he told me that the units were marked Part L 2006 compliant and so he thought they'd be OK. Do you happen to know if the Part L 2006 compliance means they have the required U value?
The roof lights did appear in the plans submitted to building control but their technical details did not.

 

[freddiemercurystwin]

Hmm, you're into a bit of a grey area here, if memory serves me right, in the new 2006 regs new extensions require glazing to achieve 1.8 whereas replacement windows still only require the old 2.2 (which I believe coxdomes do achieve). So technically whilst they may comply with parts of the 2006 regs to say they comply fully with 2006 regs may not be true (depending what they actually achieve). Oh FFS, it takes less time to ring them than type a load of blurb, they've just told me double skins don't achieve 2.2 and triple skins achieve 1.9 - so there you go! You'll need to get that in writing off them and get negotiating with the inspector. Your only hope is that there were building regs notes submitted with the application that stated they would only achieve 2.2 and these were approved before you commenced work otherwise you'll have to get persuading.

 

[bookworm2006]

I sent the the surveyor the specs from the cox dome website, it didn't have the U value but it did state it was part L 2006 compliant. He said this was OK and has issued the completion certificate.

Thanks for advice regarding all this stuff.

 

[freddiemercurystwin]

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