11997 Installing a wood burning stove

Hi Sue
there's a lot of info on here if you search under "stufa" or chimney or stove. Eg [url]http://www.italymag.co.uk/forums/building-renovation/11785-insulated-chimneys-2.html[/url]

[quote=suephilj;114533]We have an open fireplace in our kitchen and would like to install a woodburning stove. We have tried unsuccessfully to have an open fire, the room just fills with smoke. We think the chimney may need cleaning and so have bought brushes to do it ourselves. On closer examination of the chimney, looking up from the fireplace, there is some exposed wood in the construction of the chimney!! Obviously this makes it extremely hazardous to have a fire so where do we go from here? Could we insert some kind of liner into the chimney to make it safe, the chimney is very wide, and then insert a woodburner with a flue pipe.
Alternatively if the flue pipe went beyond this piece of wood would that make it safe?
We would be very grateful for any advice, thank you[/quote]

Your new wood stove will typically need a 6" or 7" liner that goes all the way to the top. An insulated one will draw better and be safer re. your 'bit of wood', assuming they will be reasonably far apart. A stove is about 5 times more efficient than an open fire so your wood bills will tumble and of course you don't have to lug so much around. The higher combustion temperatures tend to burn the tarry stuff so your new chimney should stay pretty clean with just a light brush every year when you strip and clean the stove. Incidentally I did some sums last night to compare the cost of wood energy with LPG ... I make it that gas is 7.44 times more expensive than 20% wet wood... yeeouch! Kinda makes it a no brainer to connect a huge stufa to the heating and then turn the gas off.

In fact there is research that an open fireplace can actually make your house colder; this is because 90% of the energy goes out the chimney and in extreme cases the draw of the chimney pulls the heated air out of the building as well.

Sagraiasolar is correct a stove would be more efficient - I wouldn't go so far as to say 90% more efficient but certainly more economical in the long term. The important thing to remember is to use only seasoned timber as the tendency for most is to shove a big lump of damp wood and reduce the draw this only exacerbates resin build up in the chimney - the cause of chimney fires.

As far as turning the gas off unfortunately that's not an option unless you like cold showers as 40% of our heating needs goes to hot water usage. Can be as low as 30% if there are no kids.

As regards costs 7.44 times cheaper than gas is a little excessive. Gpl is about 12 cents/kW, wood (seasoned) ~3 cents/kW and wood (unseasoned) 5/6 cents/kW. Rather depends on your negotiating skills.:smile:

Lotan thanks for your figures which imply a ratio of 4:1 Even that is pretty amazing. My calcs were based on the prices I pay for GPL and wood and calorific values of 30Mj/Kg for gas and 19Mj/Kg of wood. Of course big variances would come from whether the gas figure is net or gross (latent heat of the water product) and I'm not sure whether it was. Also the exact water content of the wood I used was a guess of 20%. Would it be fair, do you think, to agree that the ratio is 4:1 or better? 4:1 ties in with the real world because I run the gas boiler for 40 mins a day, winter and summer - costs Eur1,200 a year and I run a 12Kw stufa day and night for six months for the same cost.

Thanks so much to everyone who replied re us installing a wood burning stove.
I will definitely follow all the links and then when we return to our house in Abruzzo in May we will be armed with all the information.
Sue

[quote=sagraiasolar;114585]Lotan thanks for your figures which imply a ratio of 4:1 Even that is pretty amazing. My calcs were based on the prices I pay for GPL and wood and calorific values of 30Mj/Kg for gas and 19Mj/Kg of wood. Of course big variances would come from whether the gas figure is net or gross (latent heat of the water product) and I'm not sure whether it was. Also the exact water content of the wood I used was a guess of 20%. Would it be fair, do you think, to agree that the ratio is 4:1 or better? 4:1 ties in with the real world because I run the gas boiler for 40 mins a day, winter and summer - costs Eur1,200 a year and I run a 12Kw stufa day and night for six months for the same cost.[/quote]
That seems quite expensive for everything, 3 systems and still spending E2400. What size house and is it radiators or underfloor heating?

[quote=Geotherm;114675]That seems quite expensive for everything, 3 systems and still spending E2400. What size house and is it radiators or underfloor heating?[/quote]

The 2,400 is pre solar heating and will now be less, and of course this includes cooking too. The house is 300 m2 with underfloor heating below and rads above with towel rails left on all the time. We keep the house very warm as we can't stand being cold. We like hot showers with lots of flow for multiple users and we get this from a 160Kw heat exchanger.

Sorry Sagraisolar you obviously didn't insulate the house very well. Solar's not going to help you that much during the autumn/spring soltices. It'll just pre warm some of the water so expect high bills over the winter. Summer time you'll save a bundle.

We paid last year €900 for heating and hot water year round for our 300m2 house and we heat the pool to 28/29ºc for 6 months of the year. €700 for wood and €200 for gas including cooking. The house has a constant 18-24ºc year round temperature.

What's the 160kW exchanger for??? You should contemplate insulating the house - as I've said on innumerable threads - insulation is the single most efficient and cost effective method of reducing your energy running costs. You want a minimum of 12cms in the walls 30cms in the loft/roof space and 20cms in the floor slab. :smile:

[quote=sagraiasolar;114679]The 2,400 is pre solar heating and will now be less, and of course this includes cooking too. The house is 300 m2 with underfloor heating below and rads above with towel rails left on all the time. We keep the house very warm as we can't stand being cold. We like hot showers with lots of flow for multiple users and we get this from a 160Kw heat exchanger.[/quote]
I think as Lotan says, that your insulation level is about normal for an Italian house. With 300sq mtrs on normal insulation we would expect heating and hot water costs to be in the region of E1500 - 2000 per year. With high insulation, then circa E1000 -1500.Obviously costs could be better defined from a thermal analysis of the property.

[quote=lotan4850;114576]In fact there is research that an open fireplace can actually make your house colder; this is because 90% of the energy goes out the chimney and in extreme cases the draw of the chimney pulls the heated air out of the building as well.

[/quote]

This is not a trivial point - but consider it when you are needing cooling in the summer. Not only does a chimney/flue act as a draught in the winter, it can act as a heat extract in the summer: so, try out leaving your closed stove open on the hottest days....and refer to the Tuscan or Palladian ideal of the 'altana'!

[quote=Charles Phillips;114694]This is not a trivial point - but consider it when you are needing cooling in the summer. Not only does a chimney/flue act as a draught in the winter, it can act as a heat extract in the summer: so, try out leaving your closed stove open on the hottest days....and refer to the Tuscan or Palladian ideal of the 'altana'![/quote]

Charles I'm not sure that's such a good idea. If the outside temperature is 35ºc then you will be pulling in 35ºc air into the building which will heat the walls and act as an accumulator. The theory is right but should only be done with night time ventilation when the evenings and nights are cooler if that happens at all.

Naturally you will feel cooler in the draft as you will have the air changes but I think you'll find this is detrimental to night time sleep.
:smile:

Thanks Lotan and Geotherm for useful reference figures. Lotan, your figures are impressive as they include pool heating... I'd love to hear exactly how your system works. I expect to match your total costs now that the panels are running but alas I don't have a pool yet. You ask about the 160Kw heat exchanger - as my system has two unregulated heat sources - wood and solar - I store the energy in a heat store tank with direct connections to everything except the panel circuit which is via a coil. When the masses all need a shower the water is passed through the 160Kw heat exchanger so we get fresh and hot water at up to 45 litres a minute.
Not much more I can do about insulation. The house is a trad. stone job but at least the roof is double insulated and the floor has some indeterminate insulation under the heating tubes. Natch the windows are all double glazed and there are shutters both inside and outside. As you say Geotherm it's pretty standard for the type.
I agree about the poor winter performance of the panels... despite evacuated tubes, and a pre-feeder cold tank that makes the panels run for about 8 hours non stop every day they are not exactly awesome. I have a panel cooler going on test next month so hopefully I will be able to increase their size and power until they are able to make a more significant contribution to the plot.

Thought you may be interested in these figures, taken from the GSHP here. We do not have a pool, so I cannot comment on the heating cost involved with that installation.
These are taken from running hours, checked on a weekly basis, from 15/09/2008 to 16/03/2009.
Total 1495 hrs x 2.2Kw per hour = 3289Kw
Total 6 month operating costs calculated on 2008 and 2009 pricing, so it is possible to work out an average Electricity cost for the 6 month autumn/ winter/ spring period 2008 including IVA, @ 25cents per Kw and 2009 @ 30cents per Kw, due to the new pricing structure.
At 25cents Euro 822.25 and at 30cents Euro 986.70.
This is for 24 hour heating @ 19C and hot water @ 48C. In the summer months the pump only runs for about 1 hour per day solely to heat the domestic hot water in a 160 ltr tank, recharge time to regain temperature from heavy use, approx 30 mins.

Hot water production is approx 17% of pump output, as against 83% heating, averaged over the last 2 years.

Geothem - nearly as good as my figures in fact maybe better, I've got to cut, split and store the wood. then it's got to be carried in and fed into the boiler... dirty, dusty and hard work. I don't mind however as I quite enjoy it but let's see how I feel in ten years time...?

I might then even consider a pump myself...!?! :smile:

Sagraiasolar - I don't think your solar system will help at all during the winter as I said and the lack of insulation in the house will naturally not help. All heating systems have to work first against heat losses. I think you're going to have to look at the wood side to achieve higher efficiencies to do this you'll have to install if you haven't already ...

1. Draft regulator in the chimney
2. Reduce your water temperature to the taps to 45ºc.
3. Are you underfloor heated and what size is your accumulator?
4. Use regulatory equipment to stratify and zone the accumulator properly.
5. Use variable speed solar pump to achieve higher efficiences from the solar panels.
6. Sensors on the wood boiler to stop condense forming and any cooling effect.

We use the same system as you have with a 35Kw wood boiler, 2000 litre acc. tank, 40m2 solar panels, 22kw gpl condensing boiler all regulated with resol equipment with underfloor heating. However we have 14 cm insulation in the walls, 35 cm in the roof, 15 cm in the floor, no shutters inside or out, but the best k-value windows we could buy at the time of construction with a energy reflecting membrane on the inside pane.

All in an endeavour to reduce heat losses or at least keep them to a minimum.

Thanks for the numbers...I've always been fascinated by the concept of moving heat around rather than paying for it. Before I convert various units to the same thing for comparison could I ask whether the 2.2Kw is the consumed power of the pump or the delivered power... I assume it must be the latter judging from the recovery time on your 160 litre tank, and in that case the figures are truly impressive.

[quote=sagraiasolar;114739]Thanks for the numbers...I've always been fascinated by the concept of moving heat around rather than paying for it. Before I convert various units to the same thing for comparison could I ask whether the 2.2Kw is the consumed power of the pump or the delivered power... I assume it must be the latter judging from the recovery time on your 160 litre tank, and in that case the figures are truly impressive.[/quote]
It is the consumed power, pump delivered output is 10.7Kw at 35C (underfloor heating temps).

[quote=lotan4850;114730]Geothem - nearly as good as my figures in fact maybe better, I've got to cut, split and store the wood. then it's got to be carried in and fed into the boiler... dirty, dusty and hard work. I don't mind however as I quite enjoy it but let's see how I feel in ten years time...?

I might then even consider a pump myself...!?! :smile:

Sagraiasolar - I don't think your solar system will help at all during the winter as I said and the lack of insulation in the house will naturally not help. All heating systems have to work first against heat losses. I think you're going to have to look at the wood side to achieve higher efficiencies to do this you'll have to install if you haven't already ...

1. Draft regulator in the chimney
2. Reduce your water temperature to the taps to 45ºc.
3. Are you underfloor heated and what size is your accumulator?
4. Use regulatory equipment to stratify and zone the accumulator properly.
5. Use variable speed solar pump to achieve higher efficiences from the solar panels.
6. Sensors on the wood boiler to stop condense forming and any cooling effect.

We use the same system as you have with a 35Kw wood boiler, 2000 litre acc. tank, 40m2 solar panels, 22kw gpl condensing boiler all regulated with resol equipment with underfloor heating. However we have 14 cm insulation in the walls, 35 cm in the roof, 15 cm in the floor, no shutters inside or out, but the best k-value windows we could buy at the time of construction with a energy reflecting membrane on the inside pane.

All in an endeavour to reduce heat losses or at least keep them to a minimum.[/quote]

Phew Lotan - you're putting me through my paces.... here we go.
1/. The stufa has an air flow regulator.
2/. All water output is regulated down but I like it a little bit hotter than 45C
3/. Only underfloor on the ground. Rads upstairs for fast response times and cooler rooms to sleep in. The main heat store is 300 litres with and solar pre heat tank of 150 litres. This seems about right as a balance between storing energy and having rapid response times.
4/. The heatstore stratifies very well with cool floor outlets in the middle and hot a the top for rads etc.
5/. I have variable speed pump on the Resol controller but will be refining this soon, and doing some panel tweaks.
6/. The wood stove is run very hot with a hot gravity return from the store and rarely gets condensation. Yours is 3 times bigger than ours and as you spend a lot less on wood you are probably running it too cool if condensation has been an issue.

[quote=Geotherm;114741]It is the consumed power, pump delivered output is 10.7Kw at 35C (underfloor heating temps).[/quote]

Well I think I've got all the figures into the cost of energy in Euros\Mj
The numbers are taken from some slightly assumptive sums I had before, based I think on some bomb calorimeter results rather than real world equipment use, however the sentiments are probably right enough.
Wood squeezes the lead with .008 .... but you have to work for it
Heat Pump a close second with .017 .... and just the press of a button
Gas limps home a pathetic .06

That's quite enough heating chat - I need a drink.

Sagraiasolar - I don't believe you can with your current system set up make any further savings other than summertime with the addition of solar panels. Your costs will remain high at about €2.000/annum.

You have a typical Italian set up which I'm afraid is inefficient and very old school.

The only way to save is...

1. Increase current set up efficiencies which may mean rebuilding your system....

... this will help up to a point and the second ....

2. And most important is to reduce heat losses and keep thermal bridging to a minimum. This can only be done with insulation and careful solutions and application. Not to be found in Italy... although things are moving slowly in the right direction.

Why? Because your heat losses are so great and your interior ambient temperatures high exacerbating heat loss. You require an immense amount of energy to first win over heat loss during the winter months and maintain a min. recommended 20ºc indoors.

Which ever way you look you're going to need energy in one form or another wintertime which must come in the form of more wood/gas/electricity. To reduce your costs you either have to move fully over to a cheaper fuel (Wood) which means a part time job as a stoker.

... in my opinion... for what it's worth... :smile:

Lotan.
"Geothem - nearly as good as my figures in fact maybe better, I've got to cut, split and store the wood. then it's got to be carried in and fed into the boiler... dirty, dusty and hard work. I don't mind however as I quite enjoy it but let's see how I feel in ten years time...?

I might then even consider a pump myself...!?!"

If I remember rightly, your house only needed 7Kw of heating due to the excellent insulation that you had installed. On that basis, you could reduce my figures by about 25% for the same running hours.