Choosing Windows

How Many

To meet RT2012 we need 1/6 of the floor space of the house to be windows. Our current plan is about 120m2 so that means about 20m2 of windows.


The two important U values for windows are:

  • Ug for the glass
  • Uw for the entire window

What Material

I really like the look of wood and aluminium, but since the plan is to build a mortgage-free home within our budget, they are out of our reach financially. As is triple glazing. So we’re looking for double-glazed uPVC.

Luckily the U values for uPVC seem to be better than for wood (pine, anyway. Oak is way out of our reach.) Given our remit is to build the warmest most insulated house we can on our 100K budget, uPVC it is!

There’s some good info about that on this website.

What Size?

We want the biggest windows we can afford! It looks like there are some standard sizes (based on price) so it may be that we have to base our decision around that. 

Window Suppliers

Much research to do on this front as the prices and u-values vary widely.

Also want to see what price a 3-pane window with a central opening pane (the two outer ones fixed) compares to a 2-pane one.