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Woodburner output rating question


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We are looking at suitable woodburners to install in a new home.

The 2 storey house is double glazed and appears to have good wall insulation.

The room has underfloor electic heating and the other rooms in the house have electric radiators.

The actual room it will be installed in is around 55 sq metres and I believe the ceiling height is around 2.4 metres.

The total house area is 125 sq metres.

The Godin woodburner we are considering is rated at 11.5Kw.

I've seen calculations that suggest "With a head room of 2.4 meters you will need 60 to 70 watt per sqm."

Does that mean that the 11.5Kw would be a massive overkill or should I be considering the total area of the house, not just the room it will be installed in?

We want this fire (or similar) for both heat and ambiance and the look of it as well.

Thanks for any advice.

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Assuming the figure 70 watts a square metre and 125 square metres you would need 8,750 watts = 8.750 kilowatts. The fire is probably rated using well seasoned oak and will in practise produce less heat. so I would say you were about right for fire size. If the house were insulated and tripple glazed to Scandianvien standards the fire might be too big but it sounds about right to me.
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Thanks a lot Anton. Yes, that how I'd worked it but I wasn't sure whether I should be taking into account the total house area or just that of the room it will be installed in.  I agree that the stated output is going to be under optimal conditions.

Thanks again.

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hi, we were advised to use the following calculation: length in metres x width in metres x height in metres divided by either 25 (good level of insulation), 15 (average insulation) or 10(poor insulation).

eg.  l= 5m, w=4m, h=2.4m  = 48m2,

divided by 15 (room with average level of insulation) = 3.2kw.

so by this method your stove should certainly cope [:)]

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You need for a room that size 9.5kw min.

Rule of thumb when calculating woodburners size for room is 1kw per 14m3 with outside temp of zero.

Remember its better to have a bigger stove running on tickover to give the required heat than a smaller stove running flatout to achieve desired temp.


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[quote user="Mikey"]

Remember its better to have a bigger stove running on tickover to give the required heat than a smaller stove running flatout to achieve desired temp.




It may be a good idea to look at the conditions under which the stove's kW rating is measured.

Ours is a Deville insert rated at 11 kW.

I bought it for a much larger room in another house, but never installed it there.

This is stated as being obtained  as follows :-

* Under a draw of 10 Pa (I think maybe this should be 10 kPa, which equals 1.45 psi), averaged over 3 hours, with a charge of 9kg of dry non-split logs (hornbeam, oak,....) of approx. 12 cm diameter, being 3 logs.

* To obtain this output, reload onto a bed of embers of approx 500kg, being 4cm deep.

* The stated output is that obtained during this trial of 3 hours.


I tried this; the heat produced was far in excess of any fire we would normally use. We couldn't stand near it!

The problem now is that the thermostat keeps the air inlet closed most of the time, and the chimney and door glass soot up heavily.

If I turn the thermostat higher to burn cleaner, the room is too hot.

I think a smaller fire, burning harder, would be better.



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Thanks for all your answers. I guess there are some conflicting views on this and I'll need do some more research.

The cubic capacity of the actual room with the fire is going to be in the region of 55 x 2.4 = 132 cubic metres.

So it appears that the woodburner I'm looking at should be sufficient and not underpowered. Whether it is overpowered is now perhaps the question?

Just little more information... the house is in the Lot a bit south of  Labastide Murat and at an altitude of around 370 metres.

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We are in Blars about 10 miles s/east of Labastide, and at a similar altitude to you.

A couple of winters ago, the temperature up on the causse was 16 degrees below zero.

In our courtyard 13 below.

Big is Bootiful.(and warm)



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if you had a smaller fire burning harder you would then become a slave to the stove as it would need filling more often.

as with all stoves there are many differant circumstances to concider, insulation of the house, draw up the chimney, draught into the room.

if you have a bigger stove a fill up will last longer, also its better to have a higher output stove and not need the extra power than to have a smaller stove and need the extra power.


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We have a 10kW rated stove in a room of about 55m3. There is a door off to another room of the same dimensions on one side which is always open and another to a smaller room on the other side which is open or closed. The stove is perfect whether burning oak/charme or coke (to suit the situation of the moment) as it has a manual and very basic air control. It is so easy to regulate down to a minimum output or to a high output at will it's almost, but not quite like having a gass fire.

We are very pleased to have had the extra heat capacity when it's -12 oC outside as well as being able to leave the stove to idle on a couple of logs for an entire day. Have also heard of other people having a problem with thermostats not allowing a medium burn situation on some stoves and also of people converting thermostat control to manual too.

Hope this helps



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