Stone house needs heat

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malden

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I have a 800 sq ft, three room, single level limestone house that is over 200 hrs young to heat. The house is drafty and poorly insulated except for the very thick walls. I may get a 16 ft draft but nit much more. My area is wet and windy in winter. I will burn olive wood. My local dealer in Italy now carries Jotul and I am thinking about the F 500 Oslo. What do you advise?

Michael
 
That is 200 years old house, not hours. I should add that in Europe Jotul gives their ratings for stoves heating capacity in square meters. My space is about 300 sq meters and the Oslo is rated for 350 sq meters here.

When i read about some of the spaces you are heating with Jotul stoves, it seems to be much greater than what is advertised here. But I suspect you are heating well insulated, wood homes.

Cheers
 
NATE379 said:
How come your profile says you are in Massivetwoshits?
LOL
 
"Italy" is "local" to Massachusetts? Geez!!

-Soupy1957
 
I live in Richmond, but my woodstove and cabin are in WV. Same idea, except without an ocean in between.
 
If there is no insulation other than the thick walls, I'd go with a larger stove. If you ever had to get the place warmed up from being cold it would take a long time to heat those walls up.

Matt
 
heating that stone is like heating from an unfinished basement. lots of "thermal mass" if the indoors is not insulated against the stone its gonna take a lot of energy to heat up that stone. however once it gets there its not as hard in most cases to hold it there. im with the gang on this , go bigger at least by an added 30-50% in rated heating capacity if uninsulated or not well insulated. the cool walls suck up heat until they are warm enough to start "refusing" heat at which point the house would start warming quite well, takes a little time to achaieve this but its definately doable
 
Dan, Matt and Mike,

Thanks for your replies.

The walls of the house are about a meter thick. The house stays cool in summer and if it gets warm will retain the heat nicely. We have a big problem with humidity here as well.

I am a bit concerned about the amount of draft I can get as I have read that Jotul stoves need plenty. Is 14 to 16 feet enough?

In Italy there are plenty of steel stoves on the market and therm stoves that also heat the water etc. But there are few good cast iron stoves. Jotul is starting to sell here and sell pretty well despite the high price of there products.

Do any of you have experience with burning olive wood? Will it be hard enough of wood to function in the Oslo?


Best

Michael
 
Michael,

first, determine if your house is solid stone three meters thick or stone built around a timber frame. Many old stoners or brick builts in this neck of the woods (upstate NY) are veneers and you may have space that can be insulated. As stated above, you really need to get the house up to temp and keep it there. Make the thermal mass work for you.

I would consider a masonry heater in your situation. In the past they were hugely expensive, but now can be had in kit form for owner built installation at reasonable prices. Two fires a day of 30-50 lbs. will keep these heaters ( and your house) up to temp.

Ehouse
 
as for the olive wood, i have no clue, hopefully the locals will be able to guide you with that.

the stove will help with the humidity issue probably quite a bit as with many woodburners who are not in a specifically humid environment find out and end up with a trivit and a pot of water on the stove to increase humidity.

important question is the flue , 14-16 ft may or may not generate enough draft in ideal conditions it can in others more may be needed. is this the amount of pipe you would require to achieve the "10-3-2" rule? http://www.englanderstoves.com/help/WoodStove/10-2.html

another thing that can matter is how well "sealed" the house is. if the house is "tight" the flue may not be able to evacuate enough air to generate sufficient draft. most cases this is overcome by using an OAK however your walls would make that an interesting challenge
 
Michael, for sure you want to go much larger than what Jotul claims for their stoves because of your unique home. For an 800 sq.ft. home like that I'd be looking for something that would heat 1200-1600 sq. ft. You can err on too small of a stove very easily but it is difficult to err on too large of a stove. If that much heat is not needed then you just fill the firebox half full. As for the draft, you may not know until you install the stove. Our stove wants 14' minimum but we are 3-4' shy of that and get along just fine.
 
From what you have posted I would think the Oslo would be a good choice as long as you can top vent it, straight up. It will want all 16ft. If not, there may be weak draft issues. Olive wood should be great for burning, though I would have some pine for starting fires and milder weather. It's a very dense, high btu wood with great flames and coaling.

Where are you located in Italy and what is the average winter temperature range you will be dealing with?
 
malden said:
That is 200 years old house, not hours. I should add that in Europe Jotul gives their ratings for stoves heating capacity in square meters. My space is about 300 sq meters and the Oslo is rated for 350 sq meters here.

When i read about some of the spaces you are heating with Jotul stoves, it seems to be much greater than what is advertised here. But I suspect you are heating well insulated, wood homes.

Cheers

You may want to check the math on your square meterage.
A stove rated to heat 350m2 in your 800ft2 home will dry out your stone walls pretty well indeed.

Doing it roughly in my head puts your house at about 80m2.
 
Good eye. 350 sq mtrs = 3,767 sq ft. The Oslo might heat that amount of space... in April...in Sicily. The Oslo is rated for heating up to 2000 sq ft or about 186 sq mtrs.
 
Backwoods Savage said:
Michael, for sure you want to go much larger than what Jotul claims for their stoves because of your unique home. For an 800 sq.ft. home like that I'd be looking for something that would heat 1200-1600 sq. ft. You can err on too small of a stove very easily but it is difficult to err on too large of a stove. If that much heat is not needed then you just fill the firebox half full. As for the draft, you may not know until you install the stove. Our stove wants 14' minimum but we are 3-4' shy of that and get along just fine.


I politely disagree with that. A 1,200-1,600 sq ft rated stove is usually a 2 cu ft stove or smaller. I would go with something the next size up. Something along the lines of a 2.5 cu ft stove. My 24 inch thick stone walls soak up a TON of heat. I really can not understate how much heat those walls absorb.
 
Thank you all for your counsel.

I meant to write cubic meters instead of square meters. My 80 sq meter house has walls of 3.5 m for a total of 280 cubic meters. The Oslo is rated here in Europe for 350 cubic meters of space.

The walls of the house are all stone. There is no insulation in the walls, only some in the roof. The house is actually meant to breathe to help reduce humidity in winter and heat in summer.

I am in the hill country of Sicily at 650m. The winters can be very cold and last yerar we had a week of snow for the first time in decades, but it can be freezing for a few weeks.

I will need to exit the stove a meter through a wall and then 5 meters straight up.

I like the looks of the Oslo in brown ceramic!

Do most people choose the Oslo with arches or without?

Michael
 
malden I want to personally inspect this installation. We went to Sicily last year and loved it, but we went around the coast. The hill country still beckons us to return.

I am a little concerned about the two 90° turns in the smoke path. They are going to effectively reduce the height of the chimney by about 6 ft. That could lead to poor draft and an unsatisfying experience with this stove, especially in a milder climate.

PS: Can you change your profile to reflect your actual location?
 
Begreen

The coast of the island is great but the most beautiful areas are in the hilly regions of Etna and Iblea (Catania and Ragusa.)

I can get 16 ft straight up if I change the location of the stove to my second choice, the kitchen. There is also an optional connecting pipe for outdoor installations. Would this help?

Cheers

Michael
 
stoveguy2esw said:
heating that stone is like heating from an unfinished basement. lots of "thermal mass" if the indoors is not insulated against the stone its gonna take a lot of energy to heat up that stone. however once it gets there its not as hard in most cases to hold it there. im with the gang on this , go bigger at least by an added 30-50% in rated heating capacity if uninsulated or not well insulated. the cool walls suck up heat until they are warm enough to start "refusing" heat at which point the house would start warming quite well, takes a little time to achaieve this but its definately doable

Why is that? According to the foundation specialists I've spoken to, most of the heat loss from a basement comes from the portion that is above grade. Yes, the OPs walls are entirely above grade, but they are also 40" thick.

The K-value of limestone is about 30 times higher than fiberglass insulation, but it acts as an insulator nonetheless. 40" of limestone is equivalent to about 1 1/3" of glass insulation. Once you have pumped as much heat into the walls as they will hold given the heat capacity of limestone (close to solid concrete) and the temperature differential between inside and outside temps, heat will continue to conduct through the walls like they had 1 1/3" of glass in place. But the the convective losses through the limestone walls will be basically zero compared to a conventionally built wall because they will be virtually airtight. Studies using sensors on the outside of above-grade walls have shown that an ICF wall of R-22 outperforms conventionally built walls of twice the R-value because convective losses through the walls are eliminated with the ICF.

Given all that, I agree with Backwoods that a stove that is rated for 1200-1600 sq.ft. should be adequate for this home. After several days, the OP should experience very stable temps because of the thermal inertia created by all that mass, but with a steady state heat loss equivalent to 1 1/3" of fiberglass. In his climate, that may be all that is needed.
 
Battenkiller said:
stoveguy2esw said:
heating that stone is like heating from an unfinished basement. lots of "thermal mass" if the indoors is not insulated against the stone its gonna take a lot of energy to heat up that stone. however once it gets there its not as hard in most cases to hold it there. im with the gang on this , go bigger at least by an added 30-50% in rated heating capacity if uninsulated or not well insulated. the cool walls suck up heat until they are warm enough to start "refusing" heat at which point the house would start warming quite well, takes a little time to achaieve this but its definately doable

Why is that? According to the foundation specialists I've spoken to, most of the heat loss from a basement comes from the portion that is above grade. Yes, the OPs walls are entirely above grade, but they are also 40" thick.

The K-value of limestone is about 30 times higher than fiberglass insulation, but it acts as an insulator nonetheless. 40" of limestone is equivalent to about 1 1/3" of glass insulation. Once you have pumped as much heat into the walls as they will hold given the heat capacity of limestone (close to solid concrete) and the temperature differential between inside and outside temps, heat will continue to conduct through the walls like they had 1 1/3" of glass in place. But the the convective losses through the limestone walls will be basically zero compared to a conventionally built wall because they will be virtually airtight. Studies using sensors on the outside of above-grade walls have shown that an ICF wall of R-22 outperforms conventionally built walls of twice the R-value because convective losses through the walls are eliminated with the ICF.

Given all that, I agree with Backwoods that a stove that is rated for 1200-1600 sq.ft. should be adequate for this home. After several days, the OP should experience very stable temps because of the thermal inertia created by all that mass, but with a steady state heat loss equivalent to 1 1/3" of fiberglass. In his climate, that may be all that is needed.

Based on my experience with stone walls (I'm surrounded by them) I would still go larger than a sub-2 cu ft stove, which is what a 1200-1600 sq ft rating is usually associated with. I would go with at least a 2.3 cu ft stove.
 
malden said:
Begreen

The coast of the island is great but the most beautiful areas are in the hilly regions of Etna and Iblea (Catania and Ragusa.)

I can get 16 ft straight up if I change the location of the stove to my second choice, the kitchen. There is also an optional connecting pipe for outdoor installations. Would this help?

Cheers

Michael

Stop tempting me. The next time I go there it will be for a longer time. We really liked what we saw (Syracuse, Cefalu and some Palermo). The food was to die for.

Straight up will help, especially if you can extend the flue another 2 ft. I'm curious if Jotul is the only option. Is there a Morso dealer locally? The model 3640 would be worth looking at also. It should draft a little easier with 16 ft of flue.
 
Begreen

Yes Sicily is a gastronomic paradise and we have some great red fluids from Etna to wash it down with. Next time go to Ragusa Ibla, Modica, Scicli, these are the Baroque towns. Then trip to Etna to Randazzo, Passopisciaro, Montalbano Elicona, Novara di Sicilia. Then head to the islands, the Eolians, near Milazzo, the Agadi near Trapani etc.Magic!

I do not think we have a Morso dealer. Jotul only started selling here recently, a year ago. The 3640 looks nice but the Oslo is loaded with charm and character that would work perfectly with my house.

My Jotul dealer said I could use a 45 degree tube out of the Oslo and then go straight up 5 meters. Sound right?

Best
 
5 meters would be excellent. Softening the angle with 45s would also help. Sounds like your dealer has a good plan. Take some pictures and post them please!
 
Here's an estimation of the conductive heat losses from your walls alone (assuming a square floor plan) at 22ºC (72ºF) room temp inside and a freezing outside temp of 0ºC (32ºF). This is likely the worst heat losses of the season you will experience in your area given your stated outside temps.



q = k A ∆T / s


A = heat transfer area (m^2) = 8.6m x 8.6m x 3.5m = 259 sq.meters

k = thermal conductivity of the limestone (W/mK) = 1.25 W/mK

∆T = temperature difference across the material (ºC) = 22ºC (72ºF) - 0ºC (32ºF) = 22ºC

s = material thickness (m) = 1 meter


(259 x 1.25 x 22)/1 = 7122.5 W/hr = 24319 BTU/hr


Of course, those 3.5 meter tall walls will be a lot warmer at the top, so not only will you feel cooler down at the floor level, the heat will transfer at a faster rate at the top due to the larger temperature differential. There will be additional heat loss - both conductive and convective - from the ceiling, windows, doors, and floors, but I think most of the heat will be leaving through the walls in your case. Hope this helps some, but it seems you have already decided on the Oslo, so all I can add is that it should be plenty of gun for your needs. :)
 
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