I wanted to see if anyone has any experience with in floor radiant heating systems in greenhouses, or knows of any farms/growers utilizing it. We’re thinking of adding a hydronic system to our greenhouse before we pour the slab, but I’ve only found a few blogs and resources discussing it. We have hydromic baseboard heat in our home and love it (the coziest warmth), but obviously a relatively uninsulated greenhouse is a different beast. It seems like it might function better in some aspects than a forced air system, but also has some limitations. There are a lot of considerations.
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About a month ago I received a dump truck full of arborist waste (wood chips, leaves, twigs). Considering the amount of heat it gives off while decomposing, you might want to consider installing a non-flammable, removable floor material. If you make space beneath the floor, you could fill that space with arborist waste in the fall and let the decomposition heat your greenhouse all winter. Just a thought.
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I am on the hunt for an adequate heating element as well 
just purchased 2 different room heaters from Costco lol. rip electric bill maybe…
The voltron heater isn’t great and barely does anything except to the area directly in front.
The lasko tower fan, the same but it does say in the box that it’s only for a 150 sq ft room.
I’m thinking of getting a 300 sq ft room heater next to see if it will do anything as well.
My greenhouse is 10x20
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A heat pump ( bi-directional air conditioner) should be much more efficient than a space heater and if it doesn’t work out you can still move it to air condition a room in your house. It also doubles as a fan.
That’s especially true if you want to use your greenhouse for more than pushing plants an extra zone or extending your growing season a bit. The electric bills will pile up pretty quickly without a heat pump if you want to increase the temperature by more than a few degrees all winter.
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I have hydronic inside my house but I think it could work in a greenhouse like this:
Radiant tubing in the floor, going up to some solar water heating roof panels from Craigslist free. So far it’s pretty cheap. Then you need a single zone circulating pump which is around $100 and a basic thermostat. I think a small solar panel could power the circ pump. $300 materials?
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What are you hoping to keep the temp above vs your minimum winter temps? I’m hoping to do 50°F, but we’ll see how that shakes out in reality.
We’re breaking ground next week, hoping to get everything up before it’s truly cold.
I’m considering a walipini greenhouse to regulate temperatures both in the winter and the summer. I recommend exploring that option and investing in a geothermal system over other options.
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heat pump like a mini split? or is it another thing? I run space heater on the coldest nights and would love to cut that electric bill
You are right. I meant a mini-split.
I just learned that it’s called a heat pump when you use air to transfer heat and it’s called a mini-split when you use refrigerant to transfer heat. I believe mini-splits are more efficient.
A mini-split should reduce your electricity expenses about three times compared to a regular space heater. You can use that formula to calculate how quickly it would pay for itself. On the box it says more than triple the efficiency, but that’s in ideal conditions.
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A mini split is a heat pump but not all heat pumps are mini splits. There are air source, geothermal (open loop, closed loop, horizontal, vertical) and probably other iterations and combinations of heat pumps.
They are capable of achieving such high efficiency because the energy used to run them simply moves the heat energy of the intended system where it is needed, rather than a ‘traditional’ heating element actually using their energy to expel heat.
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Check slickdeals.net or other bargain hunting sites to look for systems. Some on sale are pretty affordable, especially when comparing what an electricity bill would be for other systems.
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That’s what I thought at first, but decided to fact-check myself before posting to make sure I don’t give the wrong info. I can’t believe somebody would just use AI to post lies on the internet. I’m shocked!
Thanks for correcting me.
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It’s ok, we are here to learn and do the best we can with the information we have!
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An update to add that we’re hoping to put down the radiant tubing this week and get the slab poured ASAP before the weather really turns. Depending on how things go, I’m guessing we’ll have the full structure up before gas/electric are run. It will be nice to have even an unheated structure immediately.
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A winter update.
We did NOT get the structure up before it turned cold. The radiant flooring is in, the gas and water are run and partially connected, the slab is poured, and it’s covered in a thick tarp for now. We went from above freezing to wicked cold and snow pretty rapidly. The structure requires caulking and it’s just been too cold.
Hoping for warmer temps in mid February since I’d love to seed start out there, but I’ve got a feeling I’ll be setting up grow lights in our sunroom again.
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Update:
The weather was very, very wet this spring and early summer, which prevented us from working on the structure (factoring in wrangling help). I then injured my dominant arm at the end of May and really rendered myself useless to doing much of anything, or wanting to do anything, for over a month.
I’m 90% healed up now, and we got the frame squared up today and the million parts sorted and labeled and in order, and are assembling the windows and doors, as well as the gable ends. I expect the whole thing to be up by Saturday. We rented a lift for a week to make things a little easier.
I already committed with an order of more citrus trees to add to my collection, as well as some other plants I think may have a chance in this environment (more figs, of course, for example). I don’t want to go too crazy until I see how the system dials in with humidity and temperature control, but I also need enough plants to entertain myself over winter.
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That’s exciting!
I can’t wait to get started with my greenhouse project. It’s going to be significantly more effort and time than I probably want to put in, but will be worth the effort in the end.
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Can’t wait to see how it turns out! Do you have a spot picked out? I agonized over placement for awhile.
We have the entire structure up and caulked. Some hiccups included terrible instructions, a few parts that needed replaced, and the doorway in the stem wall needing a little shave to fit in the door threshold on the gable end. I’m glad we did the stem wall for the extra height even though it was a bit of a pain and expense.
We just need to assemble the doors and hang them. I’m looking at insulating the north wall, as well.
I’m very much looking forward to starting seeds in here and getting a head start next season.
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Based on my elevation change, driveway location, drainage considerations, and all the other things that go into the analysis, I’ll likely be installing it not too far south of the driveway entrance. I’ve been thinking more about the location than the materials list.
I’m hoping to put a few iterations of earth batteries in the design. I have more to research on that topic.
Putting the greenhouse higher in elevation, I’ll be excavating the sunken portion and re-purposing topsoil and clay for contour swales and road base, respectively. I have too many projects and most of them are intertwined.
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I looked into earth/climate batteries a lot and couldn’t justify the setup cost vs gas heat for the amount of degrees gained (looking at data from places like threefold farm). That being said, we also would have had to pay someone to do it, which drives the cost up a lot more than if you’re resourceful and skilled enough on your own. We ended up insulating the foundation to create extra thermal mass.
I’m really interested in seeing what you come up with. I’m not 100% satisfied with my location, but I knew cooling in summer would be the most difficult aspect so I compromised with a spot that gets shade in the middle of the day.
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