Anyone have a mini greenhouse/heater combo they operate all winter in a subzero environment that they would recommend?
Winter Greenhouse
- Thread starter Jason Helmowski
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I have a 6' by 8' plastic greenhouse that all my tender plants go in over winter. In it I have a large terracotta flower pot that I used to put a candle under, it would warm the pot and be just enough to keep frost off. However it was expensive and caused a lot of condensation in the green house. I now have a jam jar filled with paraffin (Kerosene?) with a hole punched in the lid with a large nail, I made a metal tube from a piece of old can and fitted it through the hole and then threaded a cotton wool wick through it. There is a length of 22mm copper pipe runs from the hole in the bottom of the inverted flowerpot to the roof as a chimney to stop condensation. I have to stand the light to one side or water drips back down the pipe and puts it out. A largish jam jar holds enough for two days and nights. It is not a lot of heat, just enough to keep the frost off (So far, I might put in a second one this winter just in case).
Thanks that sounds like a good idea.
We re-covered our polytunnel with a plastic that had improved thermal qualities. Last year we 'double glazed' with bubble wrap and moved in our hot composting bin. It wasn't a particularly cold winter last year, but I don't think it ever went below freezing in there. We had to keep the compost bin fed - which was a struggle at times.
Ok good to know.
My challenge is keeping our polytunnel warm from around late March to last frost at end of May to lengthen my growing season. The setup above helped but I would love to be able to get just a little more warmth in there.
Whilst I haven't tried/costed this yet, I had started to get the impression that what really mattered was soil temperature - not air temperature. So it would make sense to me to get heating cables under the soil. I haven't got as far as working out whether the running costs are feasible - especially in light of increased energy costs.
My thinking is that if you could get the soil temperature up you wouldn't need to run the heating wires constantly as the soil acts like a heat sink? I wonder if it would be possible to do something with solar - so as well as the sun heating the air in the polytunnel when it shines - could you also transfer some of that sun energy into heat deep in the soil of your beds (or containers)? So no need for a battery for continuous use, but just use your actual beds as a store for heat energy from the sun?
You can get 12m of heating wire and that uses 150watts. So if you ran it off the mains for 10 hours a day that's 1.5kw a day. Shorter cables use less energy. In my case it *might* work well enough off solar as we have a lot of sun (albeit cold) in April. But you also have cost of solar panel and a transformer or similar (not sure of the technical details).
If you're interested in a bit of hard work I remember seeing someone that built (cheaply) a ground heat source system in a polytunnel at 58 degrees North (so northern Scotland). It kept the frost off in a large polytunnel during a spell of very cold weather. I'll find it if you're interested, but it was on youtube channel '58 degrees North'.
Whilst I haven't tried/costed this yet, I had started to get the impression that what really mattered was soil temperature - not air temperature. So it would make sense to me to get heating cables under the soil. I haven't got as far as working out whether the running costs are feasible - especially in light of increased energy costs.
My thinking is that if you could get the soil temperature up you wouldn't need to run the heating wires constantly as the soil acts like a heat sink? I wonder if it would be possible to do something with solar - so as well as the sun heating the air in the polytunnel when it shines - could you also transfer some of that sun energy into heat deep in the soil of your beds (or containers)? So no need for a battery for continuous use, but just use your actual beds as a store for heat energy from the sun?
You can get 12m of heating wire and that uses 150watts. So if you ran it off the mains for 10 hours a day that's 1.5kw a day. Shorter cables use less energy. In my case it *might* work well enough off solar as we have a lot of sun (albeit cold) in April. But you also have cost of solar panel and a transformer or similar (not sure of the technical details).
If you're interested in a bit of hard work I remember seeing someone that built (cheaply) a ground heat source system in a polytunnel at 58 degrees North (so northern Scotland). It kept the frost off in a large polytunnel during a spell of very cold weather. I'll find it if you're interested, but it was on youtube channel '58 degrees North'.
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Wind looks a lot cheaper possibility than solar, there are generators available under £200, but I have no idea how good they are.
We've just finished installing solar generators for our whole house. It is a bit expensive, but finally the technology is there for batteries with a long life. Older technology meant your generator would only last a couple of years, but the ones we purchased have a good 10 years in them. We have 7kw of battery storage, and 2kw of solar panels (mounted on wood stores for our wood burner which I think is nice). As savings in the bank will be eroded by inflation it makes sense to buy things that benefit you for years to come.
Early days, but it all seems to be working nicely. We could run power to the polytunnel from our home solar system.
May is the month with the most sunlight hours, so we'll be capturing way more solar than we can possibly use in the house (from memory I think average of 10kw a day). So I'm thinking we could have our big raised bed in the polytunnel fitted with a few meters of heating cable, and on the other side of the green house make a heat bed (so heating wires buried in sand). We can then stand our tubs of beans, squash etc keeping them toasty warm from may to late june when it should be heating up outside.
We should be able to get tomatoes out in late April I'd have thought. Peppers, beans, squash by mid may or earlier? Fleece over the plants at night should keep it all toasty warm even in frost.
Hi Jason. We are planning to build a greenhouse hopefully yet this fall. I can't speak from experience but I can share a link to a mini split heat pump that our builder recommends.
Let me know how it works if you get it installed thanks.Hi Jason. We are planning to build a greenhouse hopefully yet this fall. I can't speak from experience but I can share a link to a mini split heat pump that our builder recommends.
I was also looking at solar options