Choosing a Wood Burning Stove - heat ouput
Posted by Kathy Glendinning on
Heat Output: How to Choose a Wood-burning Stove
The first thing you need to consider when purchasing a wood-burning (or multi-fuel) stove is heat output vs. the size and type of room you wish to heat.
Most manufacturers quote a range of heat outputs, i.e. a 5 kW appliance will be quoted "range 2 - 7kW ", this is due to the 'intermittent' nature of the stove's operation. To obtain a heat output of 7kW you will need to top up your stove regularly, but if you let the wood die down, the heat will reduce until it finally goes out.
If you purchase a stove which has a heat capacity too large for the room in question, you will essentially create a ridiculously space. Ideally your stove should heat the space to 21°C regardless of the weather outside to accomplish this, i.e 5kWs of heat are required on a cold winters day whereas a mild day will only require 2.5kW of heat.
There are two elements which drive heat output...
The volume of air in the room
The level of insulation and air flow in the room.
How to calculate the volume of air:
Measure the length, width and height of the room in metres multiply the three numbers to get the volume in cubic metres.
i.e. a room 5m long, 8 wide and 5 high would give you 400m3
Measure the level of insulation:
Rooms can be split into three broad categories.
Poorly Insulated - Old houses (pre-1950's) with a lot of draughts.
Moderately Insulated - Houses with double glazing, typically a 1990's house.
Well Insulated - Any home built after 2008 when compulsory heating standards were introduced.
Once you have determined which type of insulation your home has, you can mark it - 10 for poor insulation, 18 for moderate insulation and 25 for a well insulated home.
To calculate the heat output required divide the volume in m3 by the insulation factor. Simple.
Example stove heat outputs
|
ROOM VOLUME (M3) |
POOR INSULATION |
MODERATE INSULATION |
WELL INSULATED |
|
25 cubic metres |
2.5kW |
1.4kW |
1.0kW |
|
50 cubic metres |
5.0kW |
2.8kW |
2.0kW |
|
75 cubic metres |
7.5kW |
4.2kW |
3.0kW |
|
100 cubic metres |
10.0kW |
5.6kW |
4.0kW |
The above is only an indication of the 'kw' required, these figures can vary. However, it is clear from the above table that for small well insulated rooms, it is not wise to install a wood-burning stove. This is due to the low kW needed, i.e. on a freezing day only 1kW will be required vs. on a mild day less than 0.5kW which is hardly a fire at all?
A stove makes a fantastic addition to any home and is a cost-effective way of heating your home.
Call 01768 862455 or visit our store.