The Very Best Smaller Greenhouses Home Heater

This has a mode called ‘no freeze’. It barely emits heat that is comparable to a leaky sink with the exception that it’s always on ‘drip’. It is barely emitting heat and with your hand over the upward distribution (the heat only flows/dissipates) up; never to the sides;

It’s intended for everything including bathrooms and greenhouses. I bought a second one to add to my 16’ attached greenhouse. I’ll bet this thing is costing me about a dollar or less a day too… it’s the most interesting heater I’ve ever seen.

My greenhouse is on a 4" concrete pad and is attached to the south side of my house under a deck extending fully over it. With this thing/heater running like it is and in addition to being protected, the nighttime temp at sunset is 50 or 51 almost each day with outside Fahrenheit temperatures at sunset at mostly 35 to 39 and when in the mornings after lows of 26 or 28 and very-similar, temps… the morning temps range 2-degrees F more or 2-degrees F less. This is thee most economical heating unit I’ve, encountered.

My greenhouse is this and bought from Farmtek: GrowSpan Estate Elite Attached Greenhouse - 6'4"W x 8'3"H x 16'6"L - FarmTek

The only mistake is there’s no foam (insulative properties) under the pad. You see sunset occurring so that’s West. That’s what is hammered from west winds pushing up and down the shutters like piano keys being played on very windy days.

Caulk the living hell out of your greenhouse inside and outside regardless of the directions that come with them stating panels shouldn’t be caulked. That’s bs. And those roof vents are useless btw/caulk them shut. Site your greenhouse eastern or northern if you don’t have a way to keep it out of full sun if you’ll be using a truly-smaller-greenhouse like this or it’s going to reach 90 and 100 degrees on sunny days when it’s 20 F outside. A 50% heavy duty fabric shade cloth will drop temps about 5-degrees on something as large as mine: 16 x 6 x 5 foot front wall and 8 foot back wall. Opening the door to pull more outside air thru will lower about another 8 F. In a greenhouse smaller than this on sunny days expect 110 degrees F. Or a 6’ x 8’ to reach almost 130-degrees (F) at late Spring.

Painted barrels did nothing here; The best thing I know to either help with holding heat or cooling when you’re in " BIG TROUBLE " is reflective insulation “put up quickly” to reflect out sunlight or hold it in. Usually that method which by the way is your last option (reflective insulation) is used to cool it down. Theoretically it could be used to keep your greenhouse warmer at night but then you would have to remove it again during the day if plants are in a stage of growth; when grafting trees in (smaller greenhouses) for example, you gotta keep temps under 95 F or they cook. 100 is definite cook of your grafts. 95 is trouble too.

You’d be very surprised what happens inside greenhouses that aren’t really larger and good sized ones like 40 feet x 20 feet. That’s pretty well the minimum size to keep climate regulated is my guess. Of course since I know Oregon conifer grafters in the Willamette Valley, I know those guys can keep the door open all winter (they seal the poly covered hoophouses…) on really rainy times to keep mud from accumulating near entrances… but other than that, they really don’t have to shut the door but if it’s going to get really cold which rarely ever happens.

Be prepared if you live in a place with sunshine that you could need to open the door during the afternoon if you have no other chance of placing your greenhouse such as under an old deciduous tree (perfect for winter + Spring) or how mine is situated. I also have a window in mine to my basement I can pull air thru to help cool it off more. There’s a 4th option for cooling and is an emergency method to heat it too.

That’s all I know.



My thought is you’d do better with a well insulated room indoors equipped with LED lights. That would give you more light and the LEDs would keep it way warmer than what you have. No need for a heater and no overheating issues.

Yours is in no mans land. Not really a greenhouse because it gets very little light. And not energy efficient because that has an R of ~ 2 at best.

I can heat my GH for $2 to 5 a day mid winter and it’s 1725 sqft. Cooling is $1 to 2 a day even in mid summer. And I can hold inside equal or less than outside even at 100F. High light level because it’s out in full sun.


(Grafts) will cook otherwise. that’s the problem in a space open without some kind of partial shade or quite a lot. Grafts will still push on the north face of a house.

I yet have to race around sometimes yet to cool it off, and, it’s the basement window that finally makes it about 89 F on sunny days when night-time temps are too cold yet to empty the thing.

that’s the issue and I’m hoping to explain my experiences to others.

I appreciate ya always Steve-



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@fruitnut it was 39 in there at 6 or 7 in the morning when 13 F. It was also 46 or 48 at 23 twice. I kept a log for about 10-days but didn’t like how sloppy it was - so I began it over.


Were you able to lift your new Samsung flat screen, Steve? Check this model. It’s like a Samsung TV, Steve! :laughing:

:muscle: Steve-man.


It does look like a TV. I’m sure it’s a nice heater. Maybe I could pick it up on a good day. And I did get my TV in place. The new TV uses about 1/4 of the energy as the old one so not much help heating the house.

I like the look of the contents of your GH. Lots of good stuff going on.

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Sounds like they need a boot cleaner by the door!

I’m glad you picked up something that should work Dax. That looks like the one you initially showed me in pm.

Definitely not a bad idea to consider the advice on further insulation from @fruitnut, especially since it seems like you generally use this greenhouse to overwinter sensitive stuff.

Even something as simple as saving/shredding Styrofoam stuff and fabricating walls to keep it in would be a good start. I’m thinking about this myself on my potential build.

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milkhouse heaters keep well houses from freezing all over America. Same heat output, dependable and 30 dollars.


They have factories in Russia, China, and Italy. Any idea this unit comes from there?

Any greenhouse surface that isn’t a significant source of light should be highly insulated. Check out the greenhouse in the snow in Nebraska. Only the south side allows light in and thus heat out. The north side and ends are insulated panels. Even the south side of that design is limited in open area.

I just insulated the north end of my GH. I used what I had on hand, mostly 3/4 inch foam board. That should increase R value from 1+ to maybe 5 at best. Reducing my heating bill by maybe 10% at most.

Putting expensive polycarbonate coverings on a north wall is a waste of money. Better to put on expensive insulation. At least the latter saves heating cost.

I even covered up one exhaust fan because it’s just a backup. And a source of cold air leaks all winter long


Looks nice @fruitnut good stuff guys!

Mine is genuinely caulked heavily and what you don’t see on the inside there’s further insulation done on the inside.

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Some people heat their greenhouse with a compost heater or biomieler :smiley:

But the problem is the compost pile must be big enough or it could freeze completely


What if the electric goes out during winter?

If it goes out for 72 days theres this.


Actually older people used long-burning graveyard candles in the greenhouse in the spring when late frosts occurred

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fruitnut,is the top of your greenhouse,polyfilm?

If anyone needs to insulate a greenhouse or anything else it’s very easy to get reused polyiso foam board. It’s often cheap enough that you can double or triple it up.

There are a lot of outfits like this around the country


That heater does look interesting. I’m using the “Dr. Heater” brand, and my main complaint is the poor calibration of the temperature knob. On the lowest setting it’s supposed to only turn on in time to prevent freezing temperatures, but mine turns on way too soon, wasting energy when I’d be fine with my greenhouse falling into the upper 30s. Here’s last night since midnight as an example:


I need something that can bend,because mine has a curvature to it.Probably the best,for my north wall right now,is reflecting foil insulation.

you’re stayed in the 46’s to 50’s range. The outside temp dropped lower than 38.

This thing I walked outside to look at it after a few days about 1 or 2 in the morning and it wasn’t emitting any heat. After that I did the same thing and it was barely ‘dripping’ heat upward. It’s awesome in my opinion.

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