Draughty New Windows

[kcr123]

Cheers folks. This is all useful stuff, because I don't have the fitting knowledge, and I'm relying on my common sense and some YouTube installation videos to try and satisfy myself about whether the job is being done properly.

To answer some of the questions:
Thermal breaks? I don't know what has been installed around the window. I can see expanding foam has been used between the bottom of the plastic cill and the wall on the window in the other room of the extension, but that looks to me just like a space filling exercise, rather than to create a thermal break.
As I mentioned above, the internal sills feel cool to me, which makes me suspect that heat is being lost under the window.

Cill top and end seals? Again, I don't know what's been done. I assume cill top refers to adding a sealant bead on the cill before screwing it to the window unit?

150 cill on a stone cill: It is a 150mm plastic cill on top of a stone cill. I bought the windows, but the spec and dimensions were checked by the builder. Is there any specific problem with this arrangement, or just the fact we have a redundant extra cill? I never thought about that until you pointed it out. It gets better and better...

 

[crank39]

Windows that are fitted onto a stone cill can either be fitted without a cill and the frame being made as face drained OR fitted onto a 'stub' fill usually 85mm, they look better and are easier to seal underneath, just aesthetics really

 

[DHFrames]

Without sounding harsh, it's the same old familiar story where the customer thinks it will work out cheaper to buy the frames themselves then get someone in to fit. Never runs smoothly, especially when builders are involved.
Can we see more pics of the windows from further back, hopefully no doors have been installed!!

 

[kcr123]

No, it wasn't a money saving exercise, or just "getting someone in". As I mentioned previously, this is part of an extension build, and the same building company has been doing all the work. I just happened to order and pay for the windows direct, instead of the builder doing it and charging me. As far as I was aware, the builder was perfectly competent to do the installation, and to be fair he appears to have done a good job on the rest of the build.

Yes, there are doors. They seem to open and close OK (!) but may try and get some pictures tomorrow...

 

[Gazman16]

He may very well be a great builder (although by his lack of any research into windows I wouldn't put my money on it) He is however a very bad window fitter.
Did you read this thread //www.diynot.com/diy/threads/water-getting-in-around-window-fix.451537/ ?
This is what you will be dealing with soon. Its a common problem when windows are fitted by builders (no offense to the good ones) and people who dont know what they are doing. You must put a bead of silicone along the back edge of the cill and a deep bead at the 2 ends of the window.
8 times out of 10 all that can be done later on is remove the windows and refit it properly.
If the windows have been rendered and plastered in it can mean having to knock off the render and damage the plaster or cutting the windows out. It can end up costing nearly as much as just having new windows professionally fitted.

 

[DHFrames]

Good old LABC, the only remaining route of compliance for the non compliant