Greenhouse heating

I know one of you geniuses has come up with some clever way to passively heat your greenhouse. I'm looking for suggestions. Ours will be small....maybe 10x16. Thanks!

 

I think it first depends on where you live. I live in North Idaho where you are not going to get away with heating tricks like water barrels (plastic) painted black to catch the sun, waste of time...I woke up this morning to 2F, not counting the windchill.

I have seen video (you tube) of people (Russians) who use an old-style radiator like system laying metal pipe around and between the beds (on top of ground but I suppose could be underground also) running to an old water boiler heated by wood. To increase heat flow, they attached a small electric water pump in-line to circulate the water. Worked really well, cheap too. They had a small farm and huge greenhouses and market the vegetables. They problem with a system like this here would be forgetting to keep wood in the stove and the water freezing in the pipes and boiler...not good. LOL! Of course, it would depend on where you live, mild winters or harsh winters.

The other thought I have had is doing like some folks do in Siberia. They build the greenhouse bed below ground, leaving just the roof above ground for the sunlight. This takes some digging, of course, but if you think it through it makes a lot of sense, earth acting as insulation while you're still catching all the sunlight that's possible. The other benefit is protection from the elements as most is below ground. I can't decide what to use for roofing that would last the winters yet still allow plenty of sunlight through but not cost an arm and a leg? In harsh climates, I think this is the best answer...maybe even stick an old wood stove in it. Dunno...

The weather here can be brutal at times. A guy down the road has built a geometric dome which I think he is using as a greenhouse which might be a good replacement for Hoop houses in this area but still need a way to heat during winter to get full use out of them and doing electric, as Dunerunner pointed out, is simply not cost effective and sustainable.

 

I'm in 6b so it doesn't get terribly cold although we always get around 0 a few days a year. Even colder than that this year with that Arctic blast that came through.

I've thought about digging it into the ground but it would have to be into a slope to get any sun at all between mid November and March, just because of the sun path and the high ridges around us. Really cuts down my options. The only flat area with exposure is below our shallow well and the water table gets pretty close to the surface this time of year...a couple mountain streams come together right here...just the way the hydrology works.

The water barrels would probably help but that's a lot of lost square footage. In a small area.

I did see a guy on YouTube today that piled up their woodchip compost against the greenhouse and had a small DC fan to pull the heat from that into the greenhouse which was fairly ingenious. I guess I could fashion some sort of cleaner version of that with a large container....or multiple containers. We have endless leaves, hay waste and sawdust from our sawmill. Draw heat from that in the winter and then have ready made compost for the greenhouse in the spring.

I'll continue to research!

 

@Hillbilly549 "...and the water table gets pretty close to the surface this time of year."
Yeah, that can be a blessing or a curse. Our well water is almost 500 feet down, but we do get a lot of snowfall. I have slight slope I was thinking about cutting into using the neighbor's excavator, let the downwards slope keep the water away. I don't know it's just a thought and it wouldn't be very big, just enough to provide for the wife and myself. I still need to find something for the roof which will hold up to the extreme hot and cold weather but let light in for the plants. Yes, mine is also ian ongoing research project. LOL!

 

Double skin and inflated between helps a lot. Beyond that it depends on what you are going to grow. If you are going to grow tomatoes in February you are going to need to use a heat system to keep the overnight temps in the 65 degree range. I f you are only growing cool season crops you only need to keep it above the froze zone temps over nights and when the sun isn't warming it. I heated the 30x96s with pairs of 55 gallon steel barrel kit wood stoves when needed for the cool tolerant crops and the one for hot crops I ran 4 barrel kit stoves. A lot cheaper to grow greens and roots over winter than tomatoes and peppers.

 

I had an 8x10 when I lived in NC, built of clear fiberglass panels. The 10' wall faced south and in winter I hung black plastic inside on that wall. If we had any sun at all it would be really warm in there, and the raised beds seemed to hold the heat well overnight although the air temps would get as cold as outside. I did run a 1500 watt heater if they were calling for temps in the teens or we had several of those cold, gray, miserable NC days in a row. I only lost plants 1 year when it stayed in the teens and twenties for a week and I guess the dirt in the beds got too cold. If I ever do it again I would get a small wall mount propane heater, maybe even a "Little Buddy", so I could get heat and humidity and the humid air holds heat longer.

 

This guy and others like him go below ground and use low tech geothermal heating. You have to move a lot of dirt but then you can eliminate most of the power requirements.

Note: he also uses the buried corrugated plastic drain pipe to cool his greenhouses in the summer. I think that is potentially risky. There will be a lot of condensation in the pipes and it seems that the standing water could breed the bacteria for Legionnaires disease.

 

Whether being in troughs or just piled underneath, manure/compost under raised tables creates a fair amount of heat. Remember to turn it over.

As others have said, South facing with clear panels.

I had a greenhouse situated so that I could plumb the dryer vent into the greenhouse. We were busy during the day, so household chores got done at night... do the laundry and heat the greenhouse at the same time.

 

I will be trying in floor heat with PEX tubing from a water heater powered by wind and solar diversion. If you have enough juice a small water distiller puts out a lot of heat. I think a water coil using a wood stove would be good also. double plastic with a blower is a good idea for a greenhouse.

 

I've looked at some of the greenhouse plans and kits that are available, but I have to ask, "Why are all 4 walls and the roof made of clear plastic sheeting or panels?". The only side that needs to be transparent is the southside, to allow winter sunlight (and maybe a few months in the fall and spring). That is why I'm planning to design and build my own greenhouse, basically it will be a wood-frame shed with a transparent wall facing south. I'm planning to use 2x6 studs for additional insulation, with siding and shingle roof to match my house. The transparent panels can be covered in the summer, when the greenhouse is not in use and to protect them from the elements. A roll-up insulated blanket will conserve heat at night, automatic vents to prevent over-heating, and multiple heat sources. I also want it to be large enough for small trees.

 

Passively heating a greenhouse involves utilizing natural processes and materials to capture and store heat from the sun. Here are some clever suggestions to consider for heating your small greenhouse:

1. Orientation: Position your greenhouse to maximize sun exposure. South-facing orientation allows it to receive the most sunlight during the day.

2. Thermal Mass: Incorporate thermal mass materials, such as water containers or stone flooring, inside the greenhouse. These materials absorb heat during the day and release it slowly at night, helping regulate temperature.

3. Insulation: Insulate the north and east sides of the greenhouse to minimize heat loss during colder periods.

4. Bubble Wrap or Row Covers: Attach bubble wrap to the inside of the greenhouse to create an insulating layer. Row covers can also provide extra insulation during colder nights.

5. Heat Sink: Place dark-colored containers filled with water inside the greenhouse. They will absorb and store heat during the day, releasing it at night.

6. Trombe Wall: Build a solid wall (trombe wall) on the north side of the greenhouse. The wall absorbs sunlight during the day and releases heat at night.

7. Underground Heat Storage: If feasible, consider an underground heat storage system where pipes circulate air from the greenhouse through an underground tunnel or thermal mass before returning to the greenhouse.

8. Solar Collectors: Set up solar collectors (thermal panels) outside the greenhouse to capture heat and circulate it inside using fans or natural convection.

9. Ventilation: Proper ventilation is crucial to regulate temperature. Use automatic vents or louvers to prevent overheating during sunny days.

10. Mulching: Covering the ground with mulch helps insulate the soil, which can contribute to maintaining a stable temperature.

11. Reflective Surfaces: Use reflective materials inside the greenhouse to bounce sunlight around and maximize its penetration.

12. Compost Pile: Position a compost pile outside the greenhouse, as it generates heat as it decomposes, which can then be directed into the greenhouse.

13. Cold Frames: Set up cold frames on the south side of the greenhouse. They can capture heat and transfer it to the greenhouse during colder nights.

14. Deciduous Trees: Plant deciduous trees strategically to provide shade in the summer while allowing sunlight to reach the greenhouse in the winter.

Remember that the effectiveness of these methods can vary based on your climate, local conditions, and the specific design of your greenhouse. A combination of these techniques might be the most effective solution for your needs. Additionally, monitoring and adjusting your greenhouse's environment regularly will help optimize its heating efficiency.