Fire Size Calculator

Size of Fire needed
As a general rule of thumb you will need 1 kW of heat for every 15 cubic meter of space to be heated.

To calculate what size of fire or stove you will need, measure the width, length, and height of the room or space and multiply the three figures together to obtain the cubic area of the space to be heated. For example, if the width of the room is 4m, the length 8m and the room is 2.8m in height the cubic area or total volume of the room is:
Volume m3 = Width x Length x Height = 4m x 8m x 2.8m = 89.6 cubic meters.

Once   the cubic area of the space to be heated is known you then need to determine the level of insulation within the house and room.  If the house is a new build, built to modern building regulations, with good insulation and only prone to minimum heat loss and is fitted with double glazing, insulated cavity walls, a minimum of 100mm of roofing insulation, good draught proofing, and floor insulation then divide the volume of the space by 25. If the house and room has average insulation, some double glazing and some insulated cavity walls etc then divide the volume by 15. If the home is poorly insulated with little or no double glazing then the volume of the space to be heated needs to be divided by 10.

Using the Calculator
Alternatively, use the fire size calculator provided.

Enter your room or the space you want to heats dimensions in metres in the length, width and height white cells. Click on the table or press enter and the size of fire required in Kw will be displayed in white text for the varying levels of insulation.

Additional considerations
You may also need to take into consideration whether there is a radiator or alternative heat source within the room, such as a radiator in which case you can deduct the radiator kW output from the total heat requirement for the room from the heat output of the fire or stove.  For example if the room requires a heat output of 7 kW and the radiator heat output is 2 kW you will only need a fire with a heat output of 5 kW.   If you are in installing a gas, or electric, fire it is usually possible to regulate the heat output so your focus should be on ensuring the fire you choose has a sufficient heat output to heat the room or space required.  We would also recommend unless you just want the fire or stove for aesthetic reasons to choose a fire or stove that can heat the room or space adequately without the additional heat source as this is bound to save money rather than using two heat sources to heat a single space. However if you are opting for a solid fuel appliance such as a log burner or multi fuel stove you first have to unravel the various heat output specifications provided by the stove manufactures.




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