Windows have more than one purpose

10% of the heat in houses escape through poor quality windows and frames.


As anywhere else, you get what you pay for with windows and considering the area of glass in modern homes, can you afford to go cheap?

Areas to investigate when purchasing windows include:

1. Do they have soft ”E” coated glass? Soft “E” coating lets the heat in but not out.
2. Do they have Diamante glass for the external pane? This is very clear glass allowing even more sun through, thereby allowing the house to further benefit from solar gain. Solar gain is the natural warming of the house by heating up the thermally massive areas like concrete floors, which then give off the heat when the house starts to cool down.
3. Are they argon or krypton gas filled? These gases further aid their insulation.
4. Do they have the, now required, airtight membrane pre-fitted?
5. How many chambers are in the frames? Chambers act as air pockets improving the insulation.
6. Are the frames steel reinforced to prevent buckling? This is especially important in larger openings.

The u-value of the window will tell you a lot, but please note that some companies are quoting the u-value of the glass only and not the glass and the frame together. Get confirmation of this. A-rated windows have an energy rating certificate.

Good window installation is vital as gaps cause draughts which makes all the above pointless.
Ecodev provides an energy audit service that will identify the areas in your home that can be improved for higher energy efficiency. The result is a plan of action that can be worked on as and when finances allow, but at least it is all in the right direction and no costly mistakes will be made.

There are companies offering to replace poor quality glass with A-rated glass. This is all good and well and will improve the existing situation somewhat, however, existing PVC frames would probably be of poor insulation quality with few air chambers, buckles and gaps and this is now where the heat will escape through. As with any other insulation, it is only as good as the weakest link. Heat will always find the easiest route to escape through. In addition, the frames would probably not be sealed to the wall properly creating another weak link. Existing timber frames (in good condition) will result in a better final u-value when using the glass replacement method.
My point is, improvements are improvements and will benefit you. My question is how much? Look at the existing windows objectively, look at the condition of the frames and make an informed descision.
You will never benefit from the A-rating of a window unless the WHOLE window is A-rated.

Do you want to improve window insulation without replacing?

1. Seal up all gaps (both externally and internally) between the window and the wall.
2. Check draught stripping and replace as needed.
3. Have your curtains lined and close these at night and then open during the day to let the sun in.

Draughts are the cause of 15% of the heat in our home escaping. Draught stripping in new windows and doors is a given these days, but what about vents in the frames and are these permanently open or trickle vents (closable). Vents are important if your house currently has no/poor natural ventilation. We need fresh air in our houses. Not only is this important for breathing, but fresh air reduced mould build-up. Being able to control the rate of ventilation into and out of our homes is the key to healthy and energy efficient living.