Please use twitter to ask a question   

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...

double glazing bad investment just to save energy
  Cost:  High
  ROI:  34.7 Years
  Skill:  Specialist
  Energy Saving:  Medium
  CO2e Saving:  Medium
 How much this measure costs to install: Low : Medium : High
 ROI is the time it takes to return the investment in fuel savings for an average gas heated 3 bed semi-detached house and assumes no government incentive schemes are used: Years
 How easy this is to do: DIY-Easy : DIY-Skilled : Specialist
 How much energy will be saved with this measure: Low : Medium : High
 How much Carbon Dioxide emission will be saved with this measure: Low : Medium : High

...assuming this is the only insulation measure installed in your house you should reduce your 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 £70 each year if you are gas heated and if it cost about £5000 to install the windows the investment will payback in about 70 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 deserve, however the best case scenario of 10% savings is presented in the tables together with the associated carbon dioxide emission reductions

This table shows the savings with an energy saving of 10% by installing double glazing and the reduction of carbon dioxide emissions for 4 different energy demands, Check your bills to see what you use. 10% is at the high end of what is possible.
Financial savings by installing double glazing - per year
CO2e emission reduction - kg per year
Below average energy use for heating per year
smaller house or warmer area
Average energy use for heating per year
the average in the UK
Above average energy use for heating per year
larger house or colder area
Source of energy for heating Savings with
original energy use
10000 kWh
Savings with
original energy use
15000 kWh
Savings with
original energy use
20000 kWh
Savings with
original energy use
25000 kWh
⚡ Electricity £0.271 per kWh
£271
(233kg)
£406.5
(349.5kg)
£542
(466kg)
£677.5
(582.5kg)
⚡ Gas £0.072 per kWh
£72
(210kg)
£108
(315kg)
£144
(420kg)
£180
(525kg)
⚡ Off Peak Electricity £0.094 per kWh
£94
(233kg)
£141
(349.5kg)
£188
(466kg)
£235
(582.5kg)
⚡ LPG £0.122 per kWh
£122
(240kg)
£183
(360kg)
£244
(480kg)
£305
(600kg)
⚡ Heating Oil £0.104 per kWh
£104
(300kg)
£156
(450kg)
£208
(600kg)
£260
(750kg)
This table shows the payback time for installing double glazing based on the costs of the fuels used and various cost options for installing the insulation, 10% savings are assumed.
Source of energy for heating Glazing install costs
select yours.
Payback time with
original energy use
10000 kWh
(years)
Payback time with
original energy use
15000 kWh
(years)
Payback time with
original energy use
20000 kWh
(years)
⚡ Electric £0.271 per kWh
£5000
£6000
£7000
£8000
£9000
18.5
22.1
25.8
29.5
33.2
12.3
14.8
17.2
19.7
22.1
9.2
11.1
12.9
14.8
16.6
⚡ Gas £0.072 per kWh
£5000
£6000
£7000
£8000
£9000
69.4
83.3
97.2
111.1
125
46.3
55.6
64.8
74.1
83.3
34.7
41.7
48.6
55.6
62.5
⚡ Economy Electric £0.094 per kWh
£5000
£6000
£7000
£8000
£9000
53.2
63.8
74.5
85.1
95.7
35.5
42.6
49.6
56.7
63.8
26.6
31.9
37.2
42.6
47.9
⚡ LPG £0.122 per kWh
£5000
£6000
£7000
£8000
£9000
41
49.2
57.4
65.6
73.8
27.3
32.8
38.3
43.7
49.2
20.5
24.6
28.7
32.8
36.9
⚡ Heating Oil £0.104 per kWh
£5000
£6000
£7000
£8000
£9000
48.1
57.7
67.3
76.9
86.5
32.1
38.5
44.9
51.3
57.7
24
28.8
33.7
38.5
43.3

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."

Comments and Questions

Comments are Closed
2022 energy price hike - Elizabeth Slee  2022-09-03 07:18:10
With energy prices increasing. Money saving expert are quoting the Typical bill rising in April 2023 to £6,616/yr for the "average" household. It would be interesting to re-calculated cost benefit analysis now.
Comments are Closed
2022 energy price hike - Elizabeth Slee  2022-09-03 07:10:41
With energy prices increasing. Money saving expert are quoting the Typical bill rising in April 2023 to £6,616/yr for the "average" household. It would be interesting to re-calculated cost benefit analysis now.
Comments are Closed
It is also a great in reducing noise from outside! - Nicholas Bastow  2016-06-10 12:51:45
It is also a great in reducing noise from outside!
reply - rdh  2016-06-10 14:47:09
well there is no arguing with that!
Comments are Closed
double glazing - pip gas and oil  2012-03-16 12:39:49
Good advice from Eastleigh Borough Council. This was 100% true before Low E glass and argon filling of the glazing. 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.
Double Glazing - Richard  2012-03-16 15:27:32
Do you have any data that quantifies this observation. I can believe they are improving, but a financial justification on energy grounds requires and understanding of how much better and I doubt it is more than a few percent. 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.
Comments are Closed
Double Glazing in Warrington - Warrington Double Glazing  2010-09-10 17:27:31
This is a great piece of information about energy saving double glazing. At Cheshire uPVC Double Glazing http://www.cheshire-upvc.co.uk we are always looking to use the most energy efficient glass, and currently have A rated glass available.
Comments are Closed
thin glass - CD  2010-08-20 18:13:57
And guess what? You can actually now get very thin glass (Pilkington) that has the same thermal properties as the standard double-glazing; so all you have to do is get the glass replaced in your windows, rather than ripping the windows out. Not many people know that.....well of course not, the dg companies want to flog you a complete window, don't they? It would be ideal for period properties, retain the wooden windows and maintain traditions.
Comments are Closed