The figures shown here are based on a house with 23cm solid brick walls. The ceilings are 2.4m high. 10cm of loft insualtions is included, as well as one external wall and average sized windows.
See our guide to heating an extension to your home
There are a number of factors that will vary this and we ghave provided rough calibration adjustments to required heat. These are:
- If you have cavity walls (uninsulated) i.e most homes built since 1920 - take off 10%
- If you have cavity wall insulation you can take off 20%
- If the room is upstairs you can take off 25%
- If you have doble glazing you can take off 5%
- If you have 2 outside walls to the space then you need to add 15%
- If you have three outside walls then you need to add 35% - 40%
- If the room has a northern aspect then you need to add 10%
- If you loft is not insulated add 15%
- If your ceilings are higher e.g. Victorian properties then add 20%
Room
Size in metres |
BTUs needed to heat room to | ||
| 18 degrees celcius | 20 degrees celcius | ||
2.44 |
2.44 |
3500 |
4100 |
3.05 |
2.44 |
4100 |
4800 |
3.66 |
3.05 |
5500 |
6400 |
4.27 |
3.66 |
6150 |
7200 |
4.88 |
3.66 |
7700 |
8900 |
5.49 |
3.05 |
7450 |
8600 |
5.49 |
3.66 |
8450 |
9800 |
5.49 |
4.27 |
9450 |
11000 |
6.10 |
3.66 |
9075 |
10550 |
6.10 |
4.27 |
10200 |
11860 |
6.10 |
5.49 |
12300 |
14200 |