I’ve been a builder since passive solar was the big idea. All of this is very familiar to me. I would only add one piece of advice. Insulation. The money spent on insulation is a better way to balance the Btu’s than to keep adding more heat production. When I was building the space was for living in. Now I’m aiming at living and growing in the same building. The internet has certainly expanded the reach of these ideas.
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@clarkinks I ended up going in a rabbit hole of info with regard to greenhouse heating haha.
I think the geothermal idea is great in concept but, seems like a big undertaking. Also I’ll be moving to an area that requires a permit for every greenhouse so that may be another issue.
I’ve read conflicting information with regard to how effective using radiative heating of water drums would be. I’d imagine It would have to be quite sunny the day before which may not be true in a northern winter day.
I also wonder if I could do a microclimate within a greenhouse. For example putting a citrus plant with Christmas lights under a frost blanket, inside a greenhouse. At the very least the greenhouse would protect the plant from convective heat loss on a cold and windy winter night. I could also just bring the plants inside on the coldest nights.
I probably would aim for owari and maybe brown’s select. Probably would nix Meyer lemon, while I love the blossom smell in the winter, lot of work for that. I think I’d rule out yuzu for the same reason. At least initially.
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Growing citrus in a greenhouse is a challenge in Kansas as well. Im using backups and fail safes for backups. It is challenging in many ways. It is not a problem we can throw money at to solve since money is not the real issue. it is the challenges the harsh environment presents to us that is the issue. There are also constraints we can’t overlook in a deep in ground greenhouse. I will post photos once I work it all out and share what I do.
These are changes I’m making at the moment on paper. Then I use the radiant heat on the walls and floor. Don’t get me wrong the system is $200 overpriced there and I know there is a cheaper way. That manifold is separate grids ensuring my entire grid never fails at once by pex pipe leaking underneath. Only a small grid might fail. The extra money i spend now could pay off long term. The hot water heater would circulate the water by itself. The pump is over kill it only needs to push 1 gpm when I did the calculation. The pump and manifold could easily be eliminated , though I feel they are worth it.
Hot water radiant heat in the floor
Beveled sides on the greenhouse sloping the walls out for earth stability. To Avoid collapse at the 8 or 9’ depth. By angling walls out i increase sunlight and stabilize walls without the cost of concrete. This is similar to what i will do
Here is my daily shopping list. The list should tell you guys I’m adding a modified radiant heat system for under $500. @fruitnut do you have any suggestions based on your experience?
The front of the greenhouse will be at 36 degrees facing slightly southeast. Similar to this
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I might have some input but don’t think I’ve seen the whole plan. If you’ve laid it all out, I’ll review that. It seems like you are running in several directions at one time. The little hot water heater sounds like a drop in the bucket and may not be worth the cost. Simple is better IMO. The insulation blanket idea trumps everything else but may not be commercially developed enough yet to procure.
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what ive thought about making one would just be layers of material on top of each other and that group layered(more like overlapping) horizontally the length of your roof. was thinking like mylar, moving blanket, then concrete blanket. trying not to get too thick. maybe the mylar between those so it doesnt get tore up. open to other ideas. just came across another, used billboard tarps from outdoor advertising companies as the outer layer.
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We are definitely using a combined approach to make sure temperatures stay where they should be
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Another thought, wonder if there is any practicality to having some sort of tarp cover connected to a temperature controlled motor to use to prevent radiative heat loss/temperature inversion on cold clear nights.
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It is a really good thought but I’m not sure it will be practical for me.
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We start digging soon. My heavy equipment guy was here last night. He understands the complexity of the project. We have the plans finalized and we move on to the implementation stage.
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To further build on the sand heater these principles can be incorporated. Solar is optional
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I think I saw a similar video.
So many videos on this topic are AI generated.
Anyway - for a greenhouse do you think it makes sense to keep the northern face as transparent? Since there is no direct exposure wouldn’t it make more sense to insulate the northern facade?
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I found this series helpful. On paper the whole thing just seems so less daunting. But when you start digging and pouring footings… the number of trips to a the lumber yard… its just an amazing amount of work.
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No I think for us the south , east, west should all be transparent , but I plan to have a hill of dirt to my north and plenty of whatever I can get to back that hill up. I will paint the north wall inside black. If i can keep the green house low behind the north hill of dirt I will.
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Yes that’s what I mean. All the greenhouses I’ve seen are sold with all 4 sides transparent (perhaps for convenience) but I think the northern side should either be dark or perhaps reflective material
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Wow, I can see that some of you have difficult conditions to cope with.
I can maybe offer some advice on some of what was presented here.
Do not use glass for windows, in any house glass windows account for the most heat loss - use perspex (acrylic) instead and if possible a double layer so you have a thermal barrier for better insulation. Same with a plastic hot house cover.
If you place a heater element inside sand, you want a fine sand on top of the heater element. Just sand will have less thermal contact, and you must vibrate the sand to optimize the physical contact with the sand. The heater element must ideally never become red hot, you want all the heat conducted away from the element. A poor contact between the element and the sand means the element heat up the air around it and then heat the sand.
I like Clarkinks thinking regarding solar panels. With enough panels in (series)/parallel you can run the heater in any condition. There is always some IR coming through during the day.
Currently the solar panels are only about 23% efficient. The solar water heater vacuum tubes are around 85% efficient, If you use these tubes with the copper conductors inside that they use for high pressure geysers, and have that dump it’s heat into sand, you will have a fairly efficient heater. A drawback with this is the solar tubes heat only to about 140oC, where as a heater element can heat to a much higher (several hundred oC) temperature, and the solar tubes need exposure to the sun, which could be difficult to achieve.
I would think if you have a few sand electric heated drums and a largish slow turning fan above each blowing down over them that the space could be kept at a fairly decent temperature.
The electric solar heated system requires very little maintenance, except keeping the solar panels uncovered. The temperature inside can be regulated some by adjusting the fan speed, if off, the heat will rise to the top and when turning it will distribute the heat around the space. The fans will require power during the night from a batterie(s) which will have to be charged during the day.
With regard to heater elements, they don’t care if you use AC or DC power. An element is a dumb thing, it reacts only to the amount of current passed through it. As long as you pass enough current through it, it will heat up, irrespective of the voltage applied.
Also, a 2000W element means that is the amount of energy disposed. A 1000W element will do the same, but will take twice as long. Keep in mind that a drum full of sand have heat losses, hence a too small heater element may not generate enough heat, a too large element may not heat either if you cannot apply enough current.
If you use DC, you cannot use AC components on it because the components will burn out very quickly, DC draw arcs when switched under load and require different types of switches which uses magnets and physical barriers to break the arc when switched.
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Excellently detailed summary! Im glad you ellaborated on this , and brought up some very valiluable points not discussed yet. You seem to fully understand the plan and the backup plans. There is nothing easy to understand about some of the things I’m getting ready to do. I think it will make more since as I do it. At the same time I’m installing gutters on a barn. A 1” rain will yield around 1000 gallons of water. Our annual rainfall is typically 34”. That is the new system. The old system can catch around 1000 gallons as well.
I’m not talking about possibly useful techniques like these
https://growingfruit.org/t/smart-ideas-practical-use/15121
Im talking about everything I’m doing is proven tech. Im only combining what’s already being done.
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We are past the planning phase. Now I’m starting to put it all together. The gutter goes on the barn soon for the rain catchment for the water.
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The dirt is like concrete, that means I chose the right location. Don’t try this with sandy soil or soft dirt. This is gravel rock, mixed with clay. It has a foot or two of worn out loam on top.
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