Jan White wrote:That's about the size of our house. We've got a super basic metal box wood stove, about 15x20". I would hate to have that thing going long enough to even boil a bit of water in the summer. Even in winter, it's sometimes hard to run it hot enough for long enough to cook anything substantial without heating the house up unreasonably. I realize you'll have the mass absorbing heat, but still, it might be tough to make it work all year.
Another thing about cooking in such a small space is it produces a lot of humidity. And all your clothes smell like whatever you cooked for three days afterwards.
125 mm — 3.5 kg — 1.1 kW
140 mm — 4.9 kg — 1.5 kW
150 mm — 6.0 kg — 1.9 kW
175 mm — 9.5 kg — 2.9 kW
200 mm — 14.2 kg — 4.4 kW
230 mm — 21.6 kg — 6.7 kW
250 mm — 27.8 kg — 8.6 kW
D Nikolls wrote:
I think the first three numbers are just... wrong, by a fair bit.
8100BTUs sounds like a reasonable number to target for a propane or electric unit with a bit of extra capacity. I don't know that there is an exact conversion to wood, but I'd round up again..
My tinyhouse is 28ft long by 8.5 wide, no loft. 2x8 floor, 2x6 roof, 2x4 walls, all with roxul. Additional 1.5" roxul on the outside of the walls. So, very similar, a bit less insulation in the walls, which the broken thermal bridging in my build probably more or less balances out..?
Figure my site gets a little colder than yours, I'm in the comox valley, not too near the water.
I don't have my HRV installed yet, so there is a bit of loss to a cracked window in the winter, but otherwise it's pretty tight, and has relatively little window area at about 35 square feet.
My direct vent propane heater has a rated output of 8800 BTU.
So, that is about a 2.6KW rated output.
Judging by duty cycle, it's had a little capacity in reserve down to the lowest temps I have seen here, -10c nighttime lows; it has never failed to keep the house as warm as I want, which is usually pretty darn warm since I spend all winter struggling to dry out A) lots of wet work clothing, and B) the house itself due to all this humidity. Maybe it has 15% reserve on the coldest nights?
Obviously this is not a science, but I am at least confident that it has SOME headroom left, and that it does not have anywhere near 50% reserve capacity.
My feeling is that a 6000BTU output would be getting down to the minimum for those coldest nights. It's already a moderately slow process to warm the house from 5C in cold weather...
I am hoping to get a woodstove installed this summer, to cut propane out barring backup and extended absences. I am thinking a 5KW stove.
A 2.6kw rated woodstove would put a LOT less heat into the space in 24h vs the 2.6KW propane unit; there is some time wasted as the fire gets going, then somewhat variable heat output as the fire hums along, fades, is fed, hums along, fades... Most days, I'll be outside, and the fire will probably be embers or dead when I get back at lunch and dinner... All extra pronounced with such a small stove needing relatively frequent feeding.
And then you go to bed and the heat fades out in... 3 hours, maybe? So, I am rounding up, to try and get a similar total daily BTU output...
OTOH, you can warm yourself directly in front of a woodstove much more effectively; the heat from the propane unit goes up, no real radiative heating to speak of...
(Unrelated: If you are not striving to be under highway max height, why not a thicker ceiling? A good place to pick up some efficiency.. I am intending to redo mine with much more insulation now that I don't intend the house to travel highways again.)