On Tue, 18 Dec 2007 10:52:13 -0800 (PST), aem
wrote:

On Dec 18, 8:34 am, Sheldon wrote:
[snip] .... I've been contemplating a greenhouse of sorts
myself, but I'm thinking more along the lines of a smallish (12' X
12') four season shed-like structure attached to my house, I need
something substantial if it's to hold up to the winters here... [snip]
The rear of my house faces
dead south so it's in full sun all year, but even so I wonder what it
would cost to heat! hehe What a stupid question, anyone installing a
greenhouse realizes it must cost something for maintaining temperature
in cold climes...[snip]

And I'm not sure you need to think in terms of heating the whole shed/
room. A friend in Oregon has a stand-alone greenhouse about 8' x 12'
which he heats only a few days per the typical winter when they get a
hard freeze. The rest of the time he uses some kind of warming
devices that just keep seedbeds and pots/trays warm. Task lights on a
timer targeted for specific plants when he wants to jumpstart
something. This approach, he says, minimizes the electric bill. -
aem


I saw an ingenious greenhouse that was heated with decaying compost
under the floor. Steam continues to pour off the top of our compost
piles year round. I'm sure the "cost" of doing this is maintaining
the compost pile, but it can work well with the proper care.