So I need some help. I have a large 20x12ft greenhouse here that I'm trying to keep heated during the winter nights. During the day is usually fine as with the doors closed it easily heats to 80+ in there, but during the night I have only this little heater going to keep things warm. I siliconed all of the panels so keep some heat in that's about it. I only have one 20 amp circuit there so I can do much more in terms of adding another heater. Any suggestions? Also the hose i have in the picture is a heated one as temporary for the winter so i can water it still. I have another one under ground I use during the summer. Most of the other plugs are fans, and lights.
by abruzzo88
18 Comments
I’ve suggested thermal mass for similar – black containers, under tables w/ most sun exposure. Stack a wall of them – sand or similar in them would hold heat and release slowly overnight. May give you those few extra degrees.
*I just posted this comment in a post about my 4 seasons greenhouse in the Oregon Coast Range Mountains -*
For most of the winter, we get by with the heat from four 4-foot long 400 watt heavy duty thermostatically controlled propagation mats, which we use to keep our salad greens and sensitive plants happy. There are two horizontal airflow fans that help to distribute the heat around the greenhouse, ensuring that even when the outside temps drop below freezing, it’s still mid 50’s in the greenhouse.
For really cold bouts, I pull a reflective thermal curtain across the grow light support struts that are about 8 feet above the floor. This helps to keep the heat from radiating up into the 12 foot high ceiling area.
I had a 20×10, heating it was a huge pain!! I ran a 35A 220V breaker with a 7500W heater, my electric bill doubled and it was still too cold.
This year I “downgraded” to a 12×14, then bought a cheap 6×6 to go inside of it. I’m still using the 7500W to keep the main house at 50F, but put a tiny desk heater inside of the 6×6 to keep my tropicals at 60F. So far it’s been a lot cheaper, and my plants are doing great 😊
Insulate, insulate, insulate. Any heater is only as good as the insulation to help keep that heat in.
Foam board on the walls, especially northern and under/behind the tables, etc.
Had to add an extra layer of 12 mill poly tarp that is translucent , after all it kinda feels like wrapping a big gift each Nov 1st. Company i ordered from is out west in manitoba . Need to keep my 300 orchids happy all winter long
https://preview.redd.it/xusb108clxyf1.jpeg?width=2248&format=pjpg&auto=webp&s=be3376b7527a6169cb62e558a15941015a7dc1a2
[northern greenhouse](https://www.northerngreenhouse.com/catalog/)
You could scrap and level the floor a bit lay down 2” pink ridge foam sub adhesive schluter heated mat floor system. Cover w 1” of sand. Lay pavers over the sand for a thermal mass. Schluter system will come w a nice thermostat easy to use
A false ceiling can really help. Just some clear 6mil plastic that runs the length and is tight to the edges. Reduces the heated space and creates a secondary space between it and the ceiling that acts as additional insulation.
I’ve used 2 x 1500w space heaters on low (2400w combined on low setting) on separate thermostats. And a ventless propane heater on super cold nights. This keeps my 10×20 greenhouse above 40°F all winter. We had a few super cold nights, down to -11°F where it struggled a bit and I also ran a diesel heater.
Never actually used one but I’ve seen Chinese Diesel Heaters recommended before – looks promising.
Look at a small diesel heater the only power it needs is a 12v transformer. I use one as primary heat on a 10×40 with ng backup. I think I paid $100 on Amazon for it and I use 5-10 gallons of fuel a week PS find somewhere that sells non tax red diesel
I just installed SolaWrap UV-stabilized bubble insulation in mine. Usually it’s supposed to be a standalone greenhouse film but adding it to my existing covering adds a 1.72 R-value plus whatever I get from the airgap in between materials. Was previously just using a single sheet of poly film, so I am expecting a 66-68% reduction in heat loss. SolaWrap is expensive, but insulative/reflective foam panels from the hip down plus something light-transmissive like bubble wrap from the hip to the top should get you significant gains.
I use a diesel heater in my 6×6 greenhouse. It keeps it low 70’s even when below freezing. I am the ordering the reflective insulation and will wrap use that too. I read somewhere to use the Large plastic bubble wrap … I am considering it as an extra layer of insulation
I am not a mechanical engineer. I got 2 ideas for you that i never tested or researched. Start active compost in the greenhouse? it’s another whole job but it will add heat to the system. Solar pool heaters? water can hold significantly more heat energy than just the air in the greenhouse. you’d need like a reservoir in the greenhouse that exchanges heat into the air or maybe you can use it for irrigation if you refill it.
I have that same exact heater and posted about it last winter. Not sure if you are one of the people who asked me about it or not. This year to prep for winter since it’s already been getting pretty cold, and I have a BUNCH of tropical plants and seedlings in there currently (zone 8A/B) I’m actually having the electric company come this Thursday and trench 18in deep and add a dedicated line and fuse to put in the greenhouse so I can run 2 heaters. Putting one in the front and one in the back. I’ve also silicone sealed all cracks and built up a leaf boarder around the outside about 4-5 inches high. Let’s hope all that works. Mine during the day is still getting up to about 100F
Do you have a boiler heating the house?
Agribon row covers suspended inside with wires
Hopefully your long walls are facing north and south. Then, if you insulate your north wall and north roof, and most of your east and west walls you can cut your heat loss in half without significantly reducing your heating season sunlight. Seal up as many air leaks as you can. If you are handy, you might DIY a small 120V heat pump, which will use only about a third as much electricity as resistance heaters.
Buy a diesel heater! 120 bucks Amazon. A fraction of the cost of electricity
This isn’t advice but I have a question about your elevated beds. I have a similar setup since I live in a tidal flooding zone and was curious how they look underneath. I think I’ve had drainage issues because I didn’t space the wood out enough. Do you have 2x4s spaces out underneath?