55.6-Years
Replacing your windows with double glazing to just save money does not actually make a lot of sense, you will reduce heat flow through you windows by at least a half and again assuming this is the only insulation measure installed in your house you should reduce you overall energy bill by between 5% and 10%. For the smaller 3 bed house assuming you save the maximum 10% of your heating costs you should save £ 60 each year if you are gas heated and if it cost about £ 5000 to install the windows the investment will payback in about 80 years.
The payback for this investment is long! If however you are replacing old windows and generally upgrading your property it is very well worth doing, or if you are just sick of the constant drafts next to your old windows. Also a pure pay back figure for double glazing does not account for the increased value of your property, so the figures in the table do perhaps present a more negative picture than double glazing deserves.
| Approx % energy saving | Approx energy saving per year |
Gas |
Electric (Std) |
Economy 7 |
LPG |
Fuel Oil |
|
| 3 bed house | 10%* | 2000 kWh | £ 90 | £ 290 | £ 146 | £ 154 | £ 132 |
| Payback time with an installation cost of £ 5000 (3 bed house) | 55.6 years | 17.2 years | 34.2 years | 32.5 years | 37.9 years | ||
| 5 bed house | 10%* | 3000 kWh | £ 135 | £ 435 | £ 219 | £ 231 | £ 198 |
| Payback time with an installation cost of £ 7000 (5 bed house) | 51.9 years | 16.1 years | 32 years | 30.3 years | 35.4 years | ||
| *This is at the high end ofthe energysavingestimate for double glazing | |||||||
Below is a typical statement regarding double glazing, from a well known energy saving website and it is frankly complete nonsense, please be aware of comments like this.
“ It is estimated that in an average dwelling the capital cost of replacement windows will pay for itself in energy savings within six years”
If this were true then for natural gas users your heating bill would have to have been over £ 1000 per year and that by fitting double glazing you would suddenly no longer need to heat your house at all. We all know this is not true. However the below represents good and responsible advice from a UK council web site (Eastleigh).
"While windows themselves lose heat quickly through the glass, as the overall area of window is small compared to other surfaces of your house (such as the walls), they only account for 5-10% of the heat lost from your home.
Double glazing has become very popular in recent years. As it is relatively expensive and the amount of heat saved fairly small, you may not wish to consider it for energy saving reasons alone. Good draught proofing and thermally lined curtains can significantly cut heat loss and will cost much less.
Double glazing is popular for other reasons such as security, noise reduction and reduced maintenance. You need to weigh up all these factors before replacing your windows.
Under current building regulations, when replacing windows they must be fitted with low emissivity glass (sometimes called 'low-E' or 'K-glass'). You should look for a FENSA registered installer to make sure the windows are fitted to building regulation standards.
Further things to consider:
• uPVC (plastic) windows do not last forever. They represent a large waste disposal problem as they do not break down. The manufacture of uPVC also uses large amounts of energy.
• A number of manufacturers offer timber framed double glazed windows which are a more sustainable alternative."
However:
I have just had to replace my windows and have used "A" rated glazing all round including a conservatory. Modern windows are now so efficient that there is NEVER any condensation on the inside! Even in the 2010/11 winter.
Reflective glass also radiates heat back into the room, so raising the radiant environmental temperature. The result is that you are comfortable at a lower AIR temperature. Therefore your heating can be turned down a degree which is a hidden benefit of all insulation.
Always use a programmable room thermostat to make use of savings.
This is not the case:- "Therefore your heating can be turned down a degree which is a hidden benefit of all insulation"- although I understand what you mean. In most houses the thermostat will be set at the same temperature with any added insulation measure, but because the heat loss is lower the thermostat will trigger the boiler to switch on less regularly and will therefore save money and energy.
Draughtproofing of sash windows and casement windows and doors