Velux windows and building regulations

20 Feb 2011
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United Kingdom
About to fit 2 new velux windows below 2 existing velux windows. Have details from Velux and about to order.

Just looked at instructions from site and they mention an underfelt collar, insulation collar and vapour barrier.

The upper windows dont appear to have these additional items.

Can anyone advise..

1. Will the windows meet B Regs for insulation etc without these additional parts.

2. Will there be any additional issues if i try to install with these extras below a window without them such as gap between rafters. I am ordering the 0007e flashing for the purpose

3 Do most people use these

Any help much appreciated


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To answer the questions
1) Yes, they will. They are optional extras. For example, I asked Velux what is the U-value of window with and without the insulation collar and the answer is the same.
2) The trimmers have to be put in same position with and withouyt the triimmers
3) I believe no

Let me briefly relay my experience. I had four Velux windows ordered (two twin openings). I also ordered insulation collar (which provides underfelt collar), vapour barrier and flashing kit.
Flashing kit is great - you need that.
Insulation & underfelt collar. First of all, my joiner was a bit upset with this. He knows how to fit a velux window and he fitted the windows in and then realised there is extra boxes and had to take the window frame off to install the insulation collar - this is all added cost to install (he was on a day rate but your roofer will probably charge you fixed extra cost). He also said that the underfelt collar is rubbish - he has to cut a line in felt to put it in so its taking something out to replace it with something else. Vapour barrier - I actually took this back as it wasn't suitable for twin windows - but having looked at it for 30quid you get a bit of strong plastic shaped like a window frame with Velux printed on it. Insulation collar - this is actually bits of plastic foam with sticky backing. Its no PUR foam and no way insulates as good.
You are far better off getting some PUR boards and some aluminium tape and using that around the window - insulation and vapour barrier all in one. I really wouldn't bother - should have spent my cash on something else.

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