Wood stove sizing

[davidj]

I've searched through the archives and can't find any good examples of stove sizing.

We're building a 20x30, 9ft walls, cathedral ceiling and open loft.  We'll have R38 in the roof, R19 in the walls and effectively R19 in the floor.  It's for weekend/vacation use at 5000ft in the Northern Sierras - in Winter it gets down to 20F at night and up to maybe 40F in the day.  Around now it's maybe about freezing at night and high 50s in the day.

The young guy from the local stove shop suggested a max 40K BTU stove (maybe 1.7 cu ft), e.g. Quadrafire Yosemite.  He emphasized not getting anything too big as the reburning doesn't work well at low output.  His dad then came up and saw the place and suggested a 65K BTU stove like a Quadrafire Cumberland Gap (about 2.3 cu ft), saying we'd need something big to heat it up on a Saturday after a week without heat.  Normally I'd trust the old guy, but then our neighbors have a similar but slightly larger cabin with a 40K BTU stove and are happy with it, although theirs is plate steel and ours will be cast iron (which I guess heats up slower).

Does anyone have any experience with modern wood stoves in a 20x30?  Anyone end up with a stove that was too big and regretted it?  Or too small?

[ScottA]

40k btu sounds about right. I have a 28k btu in my 16 x 26 cabin and it's the perfect size. I have 9' walls and cathedral cieling as well. It does take some time to get the place warmed up (2-3 hrs) but once it's warm I can cut the air way back. I have not run it in really cold weather yet though only down to 30 degrees so far this year.

[MountainDon]

I struggled with the stove selection for our 15.75x30 cabin, too.

The older guy was right in that it would be nice to have a larger stove when you first get to the closed up and cold cabin. The younger guy was right in that the modern re-burners do not reburn as efficiently with the draft turned way down.  

Last winter it took up to 5 - 6 hours to get the cabin comfortable after arriving in the dead or winter (zero F). However, that was with the ceiling insulation at only R13, now it's at R-40+. It will warm up quicker this winter I'm certain. Already I see the difference in how the cabin stays warmer and needs less fire than last fall. Also this year we have the ceiling fan working and I've already noticed an improvement in warming the back area.


My next project is to install the 18K direct vent propane wall heater. It's a Housewarmer model from Northern Tool. It's made by Empire and is the same as an Empire under the skin with 2 exceptions. It does not have remote thermostat capability, just the one on the unit. The concentric ducts have to be cut to length instead of being the simpler to install telescoping ducts.

The direct vent heater will give us a cold weather heat up boost. That could work for anybody with a propane supply.  As well it will enable us to knock off a light chill without having to build a fire. I frequently overshoot when I do that.  


For most heating the VC Aspen we bought is a good size. We have no loft, just an 8 foor single story ceiling. Last winter even with the temperature outside at zero we were warm. It was chilly by morning, but as mentioned above, now we have a proper insulated ceiling.

[John Raabe]

Don's suggestion of a combination propane unit for boost is a good one. I think you are better getting a smaller stove and running it hotter. You will have less problems with the chimney and get more out of your wood.

25 years ago when building my house the mason talked me into a big 12x12 flue for the chimney. This is what you would have for a fireplace but I've never had anything but a wood stove with a 6" pipe connected to it. When I had my small old Jotul box stove the chimney got some creosote but nothing the chimney cleaner couldn't handle every two years or so.

Now I have a bigger, handsomer Lopi stove that can really be throttled down for a long burn. What this is doing however is depositing 3d degree glazed creosote on the upper third of that big chimney. This entails a $400 cleaning job with special chains to beat the stuff off the inside of the chimney. Who knows long-term what it is doing to the chimney liner. My chimney guy wants me to spend $2,100 on an insulated 6" stainless steel liner to keep the gases warmer and reduce condensation where the chimney is out in the cold air.

My lessons from this:
• Don't oversize the stove or the flue.
• Insulate the flue if possible to keep gases warm
• A "best-in-class" insulated stainless steel chimney in a chimney box is probably better for a wood stove installation than the more expensive masonry option.