in 9a, i only need greenhouses for the winter, and mainly just at night. (1) i was wondering if anyone has tried using clay pots heated with candles to heat a small plastic greenhouse (i have a 6x4x6 and a 6x8x6 tent greenhouses)? see pic, the clay pots got very hot, too hot to touch. (2) has anyone used a small portable propane heater like the Mr Heater Little Buddy? i haven’t used it yet but it says it runs for only 5 hours, but i would need longer than that if we go below freezing for longer. (3) i thought about using multiple hot water bottles to passively heat a small greenhouse, they’d only be good for a few hours though. (4) do you think those instant hot packs used for shipping small animals and plants can be used to heat a greenhouse? please let me know if you have had success with any of these methods and what your inside versus outside temps were.
6 Likes
Barrels of water painted black retain heat at night.
Solar water heaters (similar to solar panels for electricity) could be beneficial too.
Compost piles placed inside a structure generate heat
Animals (chickens etc) placed in a structure provide heat
7 Likes
That’s a pretty cool ideal with the candles and pots. I’ve seen people use propane heaters when they knew temps would hit below they wanted and pretty happy with the results.
2 Likes
Hi @jamie -
what low temp might you see and for how long? what is the daytime high either side of that low? You dont say where you are located- that would matter a lot. My hunch is that thermal mass alone would be a good solution for you since it could give you a couple of degrees of protection and also help with high daytime temps. You might look into a buried air inlet and exhaust- sometimes called “earth tubes”. Theyll warm the air to near the ground temp at the depth theyre buried provided theres the right balance of surface area and airflow. Ditto with interior thermal mass like water. The key is to balance the amount of mass with the surface area to be able to exchange the heat effectively. Its easier said than done, but doesn’t have to be rocket science either. Small cubes like those restaurants buy vegetable oil in might be a good compromise in terms of surface to volume for water. I think they’re 4 gallons and theyre stackable. You could also experiment with masonry. Pay attention to the color/albido as it will affect how much solar radiation the masonry can absorb, which would again depend on your climate, exposure, etc. Good luck
4 Likes
Any non-ventilated combustion has the potential to produce carbon monoxide, so at the very least make sure you open it up and ventilate it well before you go in there to hang out with your plants the next morning after a night of burning anything.
That being said, your candle/flower-pot idea reminds me of these kinds of alcohol heaters, which use a small terracotta pot as the heat diffuser as well:
I bet something like that would work fine for a small greenhouse. I still wouldn’t use it in a small space that I’m sleeping in, like they suggest, though, at least not without a CO detector nearby.
4 Likes
zone 9a, coastal Florida panhandle. Dec, Jan, Feb is winter, Jan is the coldest, and we average in the 60s during the day and 40s at night, at least once every winter we go into the 20s. My greenhouses are too far from my house to have any pipes or electrical.
1 Like
also depending what you’re growing in there, you might consider using some remay ie floating row cover. Ive measured something like 6 degrees difference between under row cover and in open air in my high tunnel, depending. It gives protection from frost and equally important, desiccation. I was shocked when I saw the difference between crops we covered and those we left uncovered for a week or so… I don’t have any power in my high tunnel either. Wish I had sorted that out but it was a big enough push without
1 Like
of course, looking more closely at your weather, youre going to need some heat.
a little low output propane jobby would be a good idea
this was my set up the past weekend when it got cold (mid/upper 20s for the lows), cardboard all around and frost cloth bags layered on top of staked plants (tropical trees). checked when it was 30 F outside and 42 F inside. but for low 20s i need more.
2 Likes
I think the more appropriate title to this thread would be ‘Off Grid’ rather than Non-electric!
The more airtight as you can make things, the better off you’ll be! Adding additional air layers, like a greenhouse inside of a greenhouse would be a route to attempt too.
Depending on how dedicated you are, an investment in some batteries + a small space heater might be warranted and just lug them up to charge in the morning…
Obviously the next step to avoid lugging would be a small off grid solar system which could be repurposed with fans for ventilation in the summer.
The thermacube would limit time on for the space heater to an extent as well.
2 Likes
Some people on YouTube have made big compost bins inside of their greenhouses and the temperatures reach above 100F inside the pile, so stays well above freezing throughout. I’ve also seen people place the bins outside of the greenhouse and run a vent with a fan blowing the air inside.
When the weather is warm, you can use the compost in your garden.
3 Likes
one greenhouse is 6ft x 8ft x 6ft and the other 6ft x 4ft x 6ft. i don’t have a compost pile, nor is there room in the small greenhouses, they are filled with plants and i can hardly fit in there. i also don’t have animals or room for them inside my greenhouses. that is why i suggested the methods above, but it seems i can also try to better insulate the inside of the greenhouse with layers of cardboard along the walls, hanging large moving blankets from the ceiling or frame, and throwing frost cloths over all the plants inside.
1 Like