Planning a greenhouse what kind of heater?

[Rothrock42]

I planning to build a greenhouse. I'm trying to decide what kind of heating to use.

I was really liking the Southern Burner A-1 vented style. I like that it is on the floor and can operate without electricity. A member of our society has one and really likes it. Unfortunately they went out of business earlier this year

I've also heard that people recommend Williams direct vent. But I'm concerned that those weren't designed for operating in the moist environment of a greenhouse.

Are there other floor/wall mounted types that can function without electricity? If it is possible to find someone with unsold stock would it be good to buy a Southern burner? Is there some other type that I should be looking at?


Here are the details which might affect the answer:

• Portland, Oregon
• About 200 square feet to 10 or 12 feet tall a the peek.
• Great southern exposure
• Twin or triple wall polycarbonate sheeting
• Pressure treated wood frame
• Want to keep above 65F all winter
• Will have natural

I'm thinking about 25000 BTU should do that according to the various calculators I've used.

[Roberta]

I have a Williams Direct Vent heater in my greenhouse, and it seems to be holding up OK so far (has been in place for 5 years). Having had the previous heater rust out in about 8 years, I went to some effort to protect this one from the "rain" that happens when I water. I have found that corrugated galvanized panels (of the sort that are used as roofing) work well - thin enough to cut to size with a tin snips (but be careful of sharp edges) I created sort of an "umbrella" - since it is metal, it transmits heat. You definitely need to protect that top vent which isn't the ideal design for a greenhouse. The dampness doesn't seem to be much of a problem (have a bit of rust on the case at the bottom but the rest is fine) - with the pilot light, it stays warm all the time so tends to evaporate moisture.

[Ray]

I started with a standard Modine greenhouse heater. It failed on a 7°F night and cost me a 20-year collection.

I replaced it with a Reznor UDAS separated combustion heater, and it was the most efficient heater I've seen. The electronic control (which did need electricity to operate) failed many years later, was too expensive, so I decided to go with a Williams as a replacement. Like Roberta, I found it to be quite reliable.

DO NOT look for unsold stock of the Southern Burner: For one, you'll not likely find it, as existing owners have bought them up for parts, and 2) what would you do if you needed a part? Southern Burner stopped production because THEY couldn't get parts!

[Roberta]

While I have found my heater to be totally reliable, nothing in life is absolutely certain... a suggestion would be to also get a portable backup. I have a Mr. Heater Buddy, which can run on a 20 lb. propane tank, I think it maxes out at 9000 BTU but in a pinch could stave off disaster... and also can be used in the house if the tank is outside, can be safely used indoors with a 1 lb. cylinder.

[Rothrock42]

Thanks for the ideas and tips Roberta and Ray.

[Ray]

I have gone so far as to roll my gas grill into the greenhouse when desperate. Not the greatest from an air quality standpoint, but better than freezing them.