Work out how long it would take you to do the job. Multiply that by the hourly salary that you work for. Add on the materials. Then add on the VAT.
Four grand sounds the right order of magnitude.
Unless you window supplier is not Fensa registered. A self employed craftsperson making bespoke windows will probably not be registered as it's all too expensive and too much hassle.
Some firms will charge proportionally more for small units. Ask for their per square metre price and whether there is a minimum size charge.
Don't use putty. Use glazing tape and wooden bead. The unit manufacturer will probably sell rolls of tape - its a double sticky sided foam. For...
Pilkington K is just about visible in certain lighting conditions, as you describe, but Optitherm and other soft coats (which give a lower U-value) are pretty much invisible. There is an electronic detector that can identify whether a coating is present.
Er, not quite. The window has to conform to the Building Regulations but Fensa, a trade organization, is just one way of getting a certificate to demonste compliance. Getting a certificate from your Local Authority's Building Control is another way.
I'd expect to see some chipping at the point of impact if it had been broken by a stone. I've broken a unit by squeezing it into a not perfectly flat frame so it twists.
Get someone who knows about wood to look at it. It's hard to tell from a photo but Alex's pictures above look like oak. The 'figuring' produced by the meddulary rays are a sure sign of oak but you don't see these on all surfaces - it depends how the wood was cut.
Best not to varnish exterior oak - it will only fall off again after a few years. The wood will go grey and there's really nothing you can do except sit back and enjoy the natural weathering process. In a few hundred years it will look like medieval oak houses look now. Lovely. Put some...
Don't use tropical hardwood whatever you do.
Oak last longest with or without painting.
The really important thing is that the paint must be vapour permeable. Real linseed oil paint is much better than anything else. It will allow the wood to stay dry and largely explains why softwood...
More seriously, Philip, do you know why there was a move from 16mm gap to 20mm gap in igus? Did they think that more seemed better or was it that the slightly better sound insulation was worth the slightly worse thermal insulation?