Greenhouse Heating Questions.

21 years ago

Hi all!

I don't have a greenhouse yet, but I'm thinking of buying an "EasyGrow" greenhouse. www.easygrow.com It's a 10x10 greenhouse with 5' sidewalls and a 7' peak. I used their little calculator to figure the BTUs I would need to heat it and it came up with almost 30,000 BTUs!!! I'm willing to spend a little on heating costs, but that seems insane!! So here are my questions:

1. The greenhouse would be in full sun, and I was thinking of using (as I read on this forum) a combination of large and small containers filled with water and painted black. Also, I will be using dark colored "pavers" with pebbles or chipped granite in between as the flooring. Do you think this would help much for lowering heating costs?

2. According to the US hardiness zone map, our lowest temps should be around 0 to 5 degrees, which is what I used for the calculation. But on my local weather it says our average low is 30... Which would mean I only need 14,000 BTUs or so.

What do you all think? I really want a greenhouse, but it hardly seems worth it if the heating costs are going to cause me to take out a second mortgage. Hahaha. j/k

Thanks!!

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Comments (4)

cactusfreak
21 years ago
That's probally right since you would be trying to heat a clear cardboard box. (But they calculated wrong)
You can get a better greenhouse for $2000.00.
It makes me mad when I see companies selling disposable greenhouses. Use once and throw away. IMO I wouldn't give them a dollar for it.
Sorry to come down on your greenhouse but I know there are better ones.
Check out the site below and re-do the calculations.
You do not measure the lenght twice. I have never seen it that way before.
Spring seed starting is about over so you have all summer to find a better one.

Here is a link that might be useful: calculators
myrmecodia
21 years ago
You need heating capacity for the minimum temperature, not the average low. Being able to keep the greenhouse warm on an average night of 30 F won't do you any good if everything freezes solid on the one night temperatures drop to 5 F.

IMO, it would be better to pay more up front for a better insulated greenhouse, rather than paying all the time to heat a less expensive house.

Hope this helps.
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cottagefarmer
21 years ago
You might want to recheck your calculation. I tried their calculator with a 10x10, assuming 0 deg. F. outside temp and 50 deg. F. inside temp and got 11,800 btu. This is probably somewhat low since I don't think they are talking into account heat loss from air exchanges per hour. For a greenhouse of this size and assuming one air exchange per hour, increase the heat loss by about 33% or about 15,700 btu per hour. This is easily do-able with a 18,000 btu natural gas or propane unvented heater.
ladyisz
Original Author
21 years ago
Eee!! Thanks for the input everyone. :) And cactusfreak, no need for apologies. I'm always open to the opinions of people that know more than I do (and in this case, that's pretty much everyone! Haha) I had actually looked into a couple other types of greenhouses, but figured on this one because of ease of setup and the built in floor. But I'm actually rethinking it now after what everyone had to say.

Would any of you happen to know of another "brand" that has a good reputation? I'd like to keep it a reasonable price, with somewhat easy setup and something I can use (or at least leave up) year round. Any suggestions?