I’m about to start building a rammed-earth solar-heated house. This climate has cold winters, most January nights at -20C (-4F) or lower. It’s perfect for passive
solar heat, being high, dry and sunny, and only 34N. I’ve lived in
solar heated houses at our school nearby for about 20 years without backup heat, but now that I’m designing a personal space, I want to eliminate those January nights in rooms below 60F / 15C.
The house will stay warm
enough almost all days, but might want a few extra degrees, perhaps just in the living room, for some nights of January. The house will be made of thermal mass heated by an attached greenhouse. I’ve heard that perhaps a mass heater is not ideal for a situation where you want extra heat for only a few hours at a time.
Three possible sources of backup
energy:
1)
Wood is common fuel in the area. I won’t have my own
trees for several years, but I could buy
firewood.
2) Electricity is unreliable and weak in winter. It’s from Ladakh’s first largish dam, which didn’t submerge any habitats so it’s fairly benign, but the Indus is so low in winter that the supply is limited. I’m thinking of putting electric heating tape in the floors because it’s so cheap to install, and if the power situation improves someday I can use it.
3) Bottled LPG gas, which I’ll buy for cooking anyway, and heaters are cheap. Minimal investment cost and instant flexible heat, but high running cost and it’s fossil fuel ....
So I’ve been pondering three wood-heat options. The room I’m thinking of heating is the ground floor living room, and any vertical chimney will have to go through the bedroom above, and then out the flat roof. The subfloor is dry packed earth up to plinth level, and it’s easy to put a foundation in if adding something heavy.
1) A woodstove.
People here use lightweight wood stoves and just set them up from October to April and then store them outside for the summer. I would only need it for January. It requires very little permanent installation except a hole through the inter-floor and roof.
2) A Rumsford fireplace. Nobody here uses open fireplaces with masonry chimneys, so it would be exotic and, I
think, charming. I find Erica Wisner’s discussions of them very compelling. Would this be a good choice for quick heat when needed, when the rest of the house has lots of mass that is semi-warm? But I’d have to add a two-story masonry chimney into the building plan. I have no idea about the availability of chimney tiles -- the
local materials are earth, rough stone masonry, and various metal materials. Also, there are no chimney sweeps here: people normally dismantle their lightweight modular chimney pipes to clean them. So I’d have to clean the 2-storey chimney myself: is that easy for a klutz like me?
3) A
rocket mass heater. Well, of
course that’s appealing because I’ve been hanging out here at Permies. Is it possible to install one in a ground floor room and then run a chimney pipe up two storeys to the roof? The rocket would be against an internal wall, the bench would run 12 feet along the south-facing wall that is shared with the greenhouse, and then it could go out the west wall at knee level or have a pipe going up two stories to the roof. I could have the vertical pipe either built into the wall, or just run a bare pipe up the corner of the rooms, with a hole in the interfloor and roof. If the pipe doesn’t have to be built into the wall, I can add it later and not worry about designing it into the building, except for keeping a knee-high hole in the west wall, which would be easy to do.
There is a chance of such good solar gain that I never want backup heat at all, but somehow I doubt I’ll be so lucky. But this chance means that maybe I shouldn’t go for a major investment but just tough it out the first winter and see how much backup heat is actually needed before choosing a system.
So the basic question I’m asking you is, for a house with plenty of thermal mass that will be just a little chillier than wanted for some evenings, would you recommend a woodstove, a fireplace, or a
rocket mass heater?
Thanks for your comments and advice!