How much does it cost to heat YOUR greenhouse?
I checked out a couple books from the library, read them (for the most part), and am in the planning stages of my greenhouse. The heating sections of the books weren't too in depth and what I got from it was that it would take a 30,000 BTU heater to maintain 60 degrees during the coldest temperatures in my area. Then I came to this site and read the "Calculate the cost of heating and cooling a greehouse" section which was much more helpful.
There are still some things that are unclear to me though. It is mostly with thermal mass and solar heating. The page I read assumed no heat radiating from the sun. I was wondering how much the sun helps to heat greenhouses in the winter. At least where I live, most of the time in the winter the sky is overcast and there are only a few days with "sunshine" where it feels warmer where the rays hit your skin. I am not knowlegeable enough in this area to really know how much of a difference that would make anyway. What I am really hoping for was someone in or close to zone 6 to have actual numbers for what they paid to heat their greenhouse to give me an idea what a normal cost would be.
A quick search on amazon for a 30,000 btu heater showed a propane one for close to $300. Reading the Q&A it said a 20 gallon propane tank lasts about 30 hours. And there went my hopes of using those. So also what I was curious of is since a bigger tank would be necessary if I were to use propane, and a company already comes to fill the tank up for the house, are there any fun extra fees if I were to ask to fill up some larger tank that I purchased elsewhere. Or would it be dangerous to fill a smaller one up with the big one from the house?
Next topic: heat sinks. From the little I read it seemed like it said the sun heats 'em up during the day then they release their magic when it gets cold at night. What I thought was it seemed like they would consume heat from the heater anyway and if I left the thermostat on the heater at a constant 60 degrees there would be no temperature differential for any thermal mass to release it's energy. Due to the amount of interest in this area I assume there is more to it that someone can fill me in on.
When I first got the idea of building a greenhouse, a year round one was really what I was hoping for. Something I could grow all neat different kinds of tropicals in. My house doesn't really have to many sunny windows not to mention items that the cat won't leave alone. (For an extended period of time I should mention, being that she could walk by a plant every day for months then one day just out of the blue decides she wants to chew some holes in it.) However, realizing the costs of a year round greenhouse, perhaps just a seasonal one would be better for me and I could just keep some of the warm-region hobby plants in the house. Then I could use the greenhouse for propogation/long season crops during the growing season. It would also help if someone who was/is in this boat could chime just to give a an idea as to maintenance costs.
Any relevant information about this subject in general just to help me be more knowledgeable would be appreciated as well. Thanks.