I've been using kerosene for 16 years with no ill effects as long as you buy uncontaminated kerosene (usually meaning no water) and keep your wicks clean. I have a modified A-frame greenhouse (gh)with old and new sections. Old is 16'L x 9'W x 8'H at the ridge with a 2 foot concrete block knee wall. The new addition is 6'L x 9'W x 10'H with a 4 foot polycarbonate knee wall. Because there is a 2 foot higher section above the older section, heat accumulates in the top of the addition. I use a fan blowing downward and another fan to circulate from front to back. I'm in zone 7. One 10K btu kerosene heater will keep the temp around 50* on a 25* night. Two 10K btu heaters will keep it around 60 degrees on nights below 25*. When I started, kerosene was $1.10-$1.25 per gallon. I only used about $50 that first year so it was economical. Now K-1 is around $3.80 per gallon. I use about 3/4 - 1 gallon per night when I need heat. I haven't needed heat except one night in the past week. This next week I will probably need heat 5 or 6 nights and both heaters 1 or 2 of those night per the weather forecast. So we are talking $6-$7 per night for 2 nights. You are in zone 5 so you get a lot more very cold nights than I do. Orchidude uses unvented gas heaters and grows Orchids, this his name. You could possibly buy an inexpensive infrared or catalytic gas heater with a thermostat which might be better for you. Today I posted a link on this forum for an online pamphlet from the U. of Georgia. Dig down a couple of layers and there is a link with a formula which will help you calculate how much heat you need to heat your gh. Then check the btu/cubic feet rating for gas. This will help determine which heater will be cheaper for you. The next time I have to buy new heaters, I'm going to buy one gas infrared heater. I hope this was helpful. - Terry

Thank you for the information. I will not be heating in winter. I will start heating around March 1st and stop heating it after nights are above 60 degrees.

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Here is the link.

Here is a link that might be useful: UGA Hobby Greenhouse booklet

If you use kerosene just make sure it is legal in your state.

In Massachusetts kerosene heater have been banned for over 10 years now.

They are legal here in Indaina.

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