Replacing wooden windows
Filed under Window Insulation.
October 3rd, 2010
Hi, I am contemplating replacing all my old wooden windows (over 50 years old and leaking) with aluminium double glazed windows.
We have an efficient wood burner for heating.
The walls are insulated and the floor has paper insulation.
We can’t insulate the roof because it is a chapel ceiling.
we have a lot of windows and were wondering about the energy effiecncy of the aluminium
windows
thanks
Liz
editor, October 11th, 2010 on 2:34 am
Hi Liz,
If your old wooden windows are leaking (and probably draughty too) that could be a good reason to replace them. However, aluminium frames do not provide as much insulation as wooden frames. Ideally you would get aluminium frames that are “thermally broken” (that is, have a rubber flange in between the inside and outside parts of the aluminium frame, to stop heat loss through the frame itself. You can see from the table of R values below how the various options for double glazing both wooden and aluminium windows compare.
Thermal Performance Approximate R Value
R value for Single glazing/ Standard double glazing/ Double glazing(low E glass)
- Timber or PVC frame- 0.19 / 0.36 / 0.48
- Standard Aluminium Frame- 0.15 / 0.26 / 0.31
- Aluminium, thermal break- 0.17 / 0.31 / 0.40
Thermal backed and lined curtains- add between R 0.3 to R 0.6 depending on thickness of material and amount of gathering.
Repalcing all your windows is likely to be expensive however and it may be that you can get by with replacing some of them, and just repairing others (and maybe getting lined curtains for them).
The most significant source of heat loss is still through your ceiling and it may be that you can get some insulation into that, either by lifting, insulating and then repositioning the roofing material or by creating a false ceiling which you can insulate.
if you would like to discuss the specifics of your situation further, please feel free to call one of our trained advisors. (There is no charge for this service) .
Best wishes,
Sarah Free ( senior energy advisor, Wellington region)