Windows - should I be worried about freezing?

kieraowl

I'm about to have an extension done in my house. We're currently have your bog standard, average rear windows, probably put in 20 years ago, on a north-east aspect. The architects' plans replace these with very large sliding doors AND window lights above. The intended supplier is Smart Systems windows (I am trying to get further details out of my builder, who is less than forthcoming over the detail). However, I'm struggling to get any information on energy efficiency ratings on their website: I do have a likely U-value of 1.5 to 1.7 though.

I am really concerned that I'm going to be cold, however. (I'm a nesh southerner, living in Sheffield). The room doesn't get much solar gain except very partially first thing. Ceilings are also going to be quite a lot higher. New heating system of wet underfloor heating under tile is intended to compensate - but will this be enough?

Windows experts, please help!

MX5huggy

Your right to be concerned. You need to calculate the heat losses and make sure there is enough capacity it the underfloor heating to cope with -5 outside. A plumber is probably not up to this.

southcoastrgi

The UFH should have been worked out from the drawings showing all the relevant information, this will give the installer a drawing of the pipework