Choosing a wood stove to supplement electric heating

[kalahaine]

Hello everybody

we recently bought a recent house (5 years) of 110m2 in Normandy whose insulation on the ground floor leaves something to be desired.
We take care of the floor and will get it right.
We currently only have electric underfloor heating which we want to supplement with a wood stove (we have eliminated the pellet for its price and the fact that in the event of a power failure we want a “back-up” solution).

I learned a bit about wood stoves but I do not know how to choose, especially because of the existing underfloor heating. We want to be able to heat the floor using the stove without overheating the ground floor.
What is more, the location of the poujoulat is not ideal since it is located against a gable wall.

How to choose the right power based on these elements?
Is it credible to think of heating the floor without overheating the appointment?
Finally, what budget do you think should be considered?
And possibly, if you have references of stoves that might be suitable.

Thank you in advance for your suggestions

[Philippe Schutt]

Considering the surface, a small stove will do the trick. 5-6 kw nominal, not +, or then with accumulation.
yes, the heat rises to the floor, often more than desired.
Do not take a device with just 70% efficiency, it feels like the boost to pass the standard. targets 75 to 80%
I like stoves with a welded sheet enclosure, it is waterproof for life. Deville, Supra for example have some in the range.

[arnaud.saussereau]

Hello,
I find myself a bit in the same situation as you.
A relatively recent house (3 - 4 years) of 85m² with attic space which could be converted in the future.
The insulation seems to be basic but not sloppy either.
Heating by electric radiator in each room + a sheet wood stove which does not suit me at all.
Indeed it is made of sheet metal (so no inertia, cold in 20 minutes !!), not at all waterproof or practical (practically obliged to lie down on the ground to see on what position is the draw hatch).
I therefore plan to change the stove and hesitate a lot between taking back a wood stove and taking a pellet stove.
Like you, I would like to be able to heat the tops later (with the advantage that the stove is practically in the middle of the house).
Being away from the house from 7:00 a.m. to 19:00 p.m., the pellet stove catches my eye because it can operate during the day while regulating the preset temperature according to a chosen time range, and saves money on electricity consumption. . By cons indeed in case of cut ..... more heating !! But I tell myself that cuts are still more and more rare and short when this happens, and that at worst I will be able to connect the stove to a generator.
What makes me the most hesitant is the real economy possible.
Indeed on a traditional wood stove, you have to count the purchase of a new stove + the wood for a heating season + a sweeping.
For the pellet stove, you must purchase the stove plus the pellets for a heating season + annual maintenance + sweeping.
Being a new owner (4 months), I have no idea of ​​the consumption of heating (whether wood or electric) for one year, and therefore can not get an idea of ​​the savings achievable and the time d amortization of these two solutions.
If someone has a track, I'm interested .... :-)
Thank you and good research to you kalahaine

[ATE.Conseil]

Hello,

Here are some answers to light your candle:
- What power: the stove power to install depends on the losses of your houses; in fact, the more your house (and even more the room in which the stove is located), the more the stove must have the capacity to provide more and faster.
The choice of sizing is therefore linked to these losses as well as to the capabilities of the device (Efficiency, location, inertia ...)
For example, when you put a log of dry wood, it will allow to obtain about 3Watts ... in a certain time (500mn for pine, 30h1 for oak ...) on these 30W, it is necessary remove the efficiency of the stove (at least 3500% to be green flame (there are 65W left) of which about 2% will quickly be found outside (draft efficiency) ... so we have 300W left to heat the interior
Then, you should know that the Temperature gradient around a stove will be of the order of 1.5 to 4.5 ° C / m depending on the leaks in your house and the inertia of the surrounding materials ...
All that to tell you that the choice of a stove like any other means of heating is to think on the basis of concrete and measurable elements ... I urge you to have a complete thermal study carried out which will certainly teach you a lot about the functioning of your home as well as on the many achievable improvements
A wood stove, pellet stove ... will cost you between 2 and 000 € (see more than 7 € if you take the accumulation) without solving the problems of discomfort ... while can to be, an infitrometry test and the correction of leaks (~ 000 €) will bring you comfort and well-being

- What energy: it is true that the log (~ 70 € / Stere) is less expensive than the pellet (~ 260 € / Tons) it is also true that the log stove does not need electricity ... but the pellets are regulated in temperature and heating time, at a better efficiency (> 90%) can be channeled (there are stoves where we can distribute the heat in the room, in two other rooms or both)
As for the boiler, it is only of interest if you connect the stove to an additional central heating ... which you do not have.

- Finally, I allow myself a remark on your comments related to the poor insulation of your house ... if your house is about 5 years old and has electric heating .... it most certainly has the label d 'Electric house' efficiency ... and therefore has reinforced insulation compared to other houses of the same age ... the problem lies elsewhere ... is that the RT 2005 gives an average house of around 250kWhEP /m².an where the BBC (and RT2012) give consumption 3 to 5 times less ...

In summary, thermal study and improvement of energy efficiency must be your food for thought BEFORE any purchase!

Philippe DESON
ATE Consulting

[arnaud.saussereau]

Thank you Philippe for all these details.

But here, the house Kalahaine as well as the mine are like new (given their age of 3 to 5 years), and in what concerns me I do not wish to undo everything to redo, even if I grant it to you, it is certainly the most efficient.
Regarding the exact loss calculation, it is not easy ... and given the low budget I have, I do not want to invest in a thermal study.
For an estimate of the necessary power I left on a need of 20 to 25W / m3.
Does anyone have any idea what 1 tonne of pellet represents in cubic meters of wood?

[ATE.Conseil]

One cubic meter of log wood provides around 1400KWh while a Tonne of pellets provides 5400kWh

A+

Philippe DESON
ATE Consulting

[arnaud.saussereau]

Thank you Philippe, thanks to this info I can put my hypotheses!

Here, as far as I am concerned, I have a power requirement ratio of 25W per m3. My house is around 300m3.

Or 25 x 300 = 7,5 Kw
I add an increase of 10% for security which makes me 8,250 Kw.

1T of pellets = 3.85 steres (5400/1400)
I was told (but I don't know how to check it) that to heat my house you would need between 7 and 9 cubic meters of wood.

Starting from the stoves that I looked at, I saw that a pellet stove with an efficiency of around 90% and a wood stove with 80% is a difference of 10% in efficiency.

So I withdraw 10% on the assumed consumption of wood, either between 6.3 and 8.1 cubic meters which I transform into pellet equivalent or between 1.64 and 2.1 Tons of pellets.

So if I summarize, my consumption would be 7 to 9 cubic meters of wood or 1.64 to 2.1 T of pellets.

I found near the stere of wood (in log of 33cm) at 60 € undelivered and 66 € delivered.
For the pellet, 280 € pallet of 67 bags of 15 kg or 1,005 T not delivered, 280 € delivered and even 304.50 € delivered if by 2T.

If I assume that I will fetch the fuel myself and that I will use the largest estimated consumption, this gives me:

For wood: 9 x 60 = 540 €
For the pellets: 588 €

A difference of € 44 for a heating season.
It remains to determine the difference in price with the purchase of the stove as well as the maintenance (around 150 € HT sweeping included)

Voila, but hey, all that starting from hypotheses, many hypotheses even .... so I don't know if I am close to reality or not ....

[arnaud.saussereau]

I correct my previous message:

I found near the stere of wood (in a 33cm log) at 60 € undelivered and 66 € delivered.
For the pellet, € 280 per pallet of 67 bags of 15 kg or 1,005 T not delivered, 345 € delivered and even 304.50 € delivered if by 2T.

Sorry.

By cons the more I read my calculations, the more I tell myself that it is necessary ... but I can not say why .... !!!