I am hoping all you smart permie homesteading people can help me out.
I am in the process of building a greenhouse totally made for old patio and barn windows. My plan is to make it 12’ by 8’. Now this is what I need to know. Thankfully we are having a mild Jan here in WI and building it is working out. But what are some of your suggestions for heating it? I know some people use a couple 100wt light bulbs and some manure. But I am looking for a more cost efficient and simple way of doing it. The Rocket Mass Stove has really caught my eye, but I’m just not sure. Or do I just get an old fashion wood stove and start it up each night? Whatever I do has to be good enough to stand -15’ to -30’. We may be having a mild winter now but I know it won’t be like this forever. Idea’s and thoughts please!!
yes, knowing what you want to grow is a great question, that way you'll know roughly how much you need to heat the room. Do you get much sun there during the winter? If so, some thermal mass, ie jugs or drums of water, rock etc might be a good option too.
A wood stove will heat the air, and some heat will be absorbed by the soil or any thermal mass you plan into the space... but when the fire's out, the heating stops, though some heat will be re-radiated from objects that have taken up thermal energy. A Rocket Mass Heater heats up a large mass of stone/brick/etc..., and could be constructed so the smoke path runs under some deep growing beds with a mass of stone surrounding the metal stove pipe, so it would warm the soil. It could also be used to simply store a lot of heat from a small amount of fuel, which would be slowly radiated into the greenhouse.
When I think of using a greenhouse for season extension, early starts, or even maintaining greens through the winter, the rocket mass heater approach is what I would be after, though that may not match your goals, or the way you are planning to use the available space. I'm working on a greenhouse design, and your question prompts me to think about a heat source for mine, too.
This is an idea I have for a project, I haven't seen details anywhere else so it's just theory. But...
You could build one wall of the greenhouse with cob and run the stove pipe through it. The cob will absorb the heat from the stove and hold it for some time after your fire has gone out, but will also just radiate the heat better than the stove on its own. It will take more time to do the cob, but it may be worth it.
I second the SHCS
IF you are trying to go all out and have an awesome greenhouse, check out CRMPI's greenhouse, "Pheonix" they have that installed and grow tropicals in the mountains near Basalt, CO
otherwise a RMH in the beds MIGHT be what you're wanting
but also, consider raising the beds up and installing a cold trench under the pathway
1) move able insulation panels. A little insulation will make a huge difference and make whatever else you do more effective. Also make sure that the green house is air tight, at least when you want it to be - big difference between it being drafty and having controlled ventilation.
2) have a base load passive heating system collecting heat from the sun or from compost etc.
3) have a peek load system for fast response and those extra cold days - this could be electrical, gas or biogas ( from a DIY bio digestor)
A rocket mass heater will be much more effective than a wood stove for this application.
Also consider building the house level with the ground (assuming you have a good south facing slope), with a flat ceiling. That way it would be really easy to put insulation panels on sliders and have them cover the ceiling (think garage door style, maybe you could even get some old garage doors.....)
First, you have to keep it warm. You can stick polystyrene board back to your north wall. Cover hear curtain on your firm at night.
Then, while the temperature goes down, you could heat your greenhouse with hot-water warmming by solar energy , hot air blower, even bath heater.
Hi All; An 8" rocket mass heater as a raised bed is an unbeatable way to go! I just went thru my first winter with one and i love it !!! Past years I burnt 12-15 full cords to try and keep things alive, with hugely varying temps, my plants were NOT HAPPY and neither was I, with 3 am trips outdoors to feed the (Wood gobbler!) ! This year i burnt apx 5 full cords and the whole room was even temp! no cold or hot spots ! Best of all NO FIRE ALL NIGHT !!! During the coldest times (-10 at night and +5 during the day) we stopped feeding the dragon around 10 at night with greenhouse temp apx 60-70 degrees , next morning at 7 am average temp inside 41-45 !