Messages posted to thread:

Judi Longstreet11-Oct-02 12:30 PM EST 4b   
Susan11-Oct-02 06:24 PM EST 6a   
DAVE11-Oct-02 09:17 PM EST   
kath17-Oct-02 09:02 PM EST 2b   
Sylvia01-Dec-03 08:36 AM EST 3b   
Dave S02-Jan-04 09:56 AM EST 5a   

Subject: heating green houses
From: Judi Longstreet
Zone: 4b
Date: 11-Oct-02 12:30 PM EST

I'm intending to build a greenhouse attached to a freestanding garage sometime in the next few years. The exposure will be SSE and although our winters can go down to below -35 degrees celsius they haven't hit -30 for the last few years. I am mostly interested in heating the greenhouse during the late winter/early spring months (March/April/may)and would like to use solar panels to do so. Can anyone give me suggestions on how I can research this? Does anyone know of any good web sites I can go to? Can anyone tell me of their experiences doing this? I live south of Ottawa if anyone knows of a good retailer in eastern Ontario. Any suggestions will be welcome.



Subject: RE: heating green houses
From: Susan
Zone: 6a
Date: 11-Oct-02 06:24 PM EST

You might want to start by talking to Lexis Greenhouses in Ottawa. They have a web site at:

Their address and contact information is:

15 Grenfell Cres. Bay 6 Nepean, ON K2G 0G3

Ottawa Area: Tel: 1 (613) 226-7358 Fax: 1 (613) 226-9148

I don't see solar panels on their site but I think they have a good reputation so you might want to talk to them and see where that leads you.

You can also go to the Suppliers listing on this site at:

and search the listings for Ontario under the category Greenhouses (near the bottom of the list in the drop-down menu...)

Subject: RE: heating green houses
From: DAVE
Date: 11-Oct-02 09:17 PM EST

I've researched green houses a bit. I'd love to have one but the cost etc. is tough for me to justify at this time. What I've found out is that heating it year round is very expensive. Solar heat is probably not what you want as it is most effective during the day and normally this is when the greenhouse is going to be absorbing sun rays anyway. Most sunny days you'll probably be opening the windows to let the heat out. Solar energy would be beneficial if you built a heat collection unit(water tank) that would store the heat during the day then release it at night. Because glass provides poor insulation, there is a lot of heat loss at night and if you had no sun during the day you would need alternative heat. Natural gas is probably the best for year round heat. If you want to extend your growing season by a few weeks/month with the use of a greenhouse, I've seen where you can line the back wall with jugs of water. The solar heat is absorbed by the water during the day and then slowly released at night. It's a very cheap way to extend the growing season by a few weeks in the spring and the fall.

Subject: RE: heating green houses
From: kath
Zone: 2b
Date: 17-Oct-02 09:02 PM EST

We have a greenhouse now in it's 2nd year of operation. It faces south,and is built against one side of our house. It is a pit type of greenhouse, you step down 3 or 4 small stairs - and there is a trenched walkway between to parallel beds - both at waist level. I use it from mid/late April til now. My tomatoes are still growing and turning red . I have had the milk jugs filled with water lining the back wall, but in the extreme heat of summer - they would begin leaking water out of the jugs. Our greenhouse in the "shoulder" grow season, gets an electric heater turned on at night, just to get keep the plants from freezing. We too, get cold winters and can't imagine trying to keep it heated year round. We didn't build our greenhouse from a kit, my hubby did the design after reading numerous books - and it looks very nice. The one thing you need to do is have enough ventalation, ours needs a 2nd vent - it reaches up to 37C in the summer on a hot day inside, and that's too much stress for a lot of plants. Good luck

Subject: RE: heating green houses
From: Sylvia
Zone: 3b
Date: 01-Dec-03 08:36 AM EST

This is not a reply really, more of a question. Does anyone know of a Canadian source for the booklet titled "Building a solar heated pit greenhouse"? Berry Hill used to have it but apparently it is no longer available.

Thanks for any info.

Subject: RE: heating green houses
From: Dave S
Zone: 5a
Date: 02-Jan-04 09:56 AM EST

I have had 3 different green houses in the last 20 years in the Toronto area. It would be impossible to heat even a small glass or plastic greenhouse in Ottawa in January with Solar.There are days if not even weeks when you don`t even see the sun. The only way to heat it is with natural gas and a small gas furnace or a 220 volt electric construction heater. There are small natural gas furnaces that require no electricity(low voltage).They work quite well and can heat a greenhouse of about 10ft by 10ft. If you depend on electricity and the power goes out at minus 30, you will loose everything in a few hours.Most tropical plants or Orchids do not like to go below 60 degrees F.Greenhouses made of glass or even double layered poly plastic do not hold the heat very well. I love greenhouses. With a bit of research, one can grow almost any thing you want from exotic orchids, well you name it and it can be grown in a greenhouse. The bottom line is that heating must be reliable in the winter and venting or cooling in the summer is just as important.

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