What questions to ask windows installer

[agamemnon]

Hello, 

I have received two quotes for 8 windows and six panes of glasses changed. 

 

The first quote is for £5000, and the quote mentions 

To supply and fit WER ‘A’ rated REHAU 70mm replacement white p.v.c.u. 
windows to match styles as discussed.

 

 

the second quote is for £4470 and in the quote the only thing about the specifications mentioned is:

 

All our windows and doors meet current building
regulations (Low 'e' glass 28mm double glazed units - with
toughened glass where required)

 

 

Are there any particular questions I should ask?

[JohnMo]

U_w value. That is the whole window U value as opposed to U_G which is just the glass.

 

How are they installing them. You really want them foamed in with airtight expanding foam. This will give a good degree of airtightness and eliminate the thermal bridge around the frame. Many will install in the hole and then cover everything leaving a void and you get mould around the window.