Thirsty_Dirt - Welcome to my world !!! Zone 3 - that is. Light bulbs (many) will work in the early spring when the plants are small - with a frost blanket over a protection cage so it doesn't touch the plants or the light bulbs - but that isn't practical this time of year! We have found the least expensive method is to run a couple of ceiling fans 24/7 to keep the warm air down in the GH and put a space heater or two on a timer. You will have to check the GH temp constant (a remote thermometer is great to track GH temps) to figure out when to run your space heater - we try to keep our GH above 40 degrees minimum. Our GH is sealed but we have to supplement a space heater when outside temps get below 32 degrees (depending how many hours the temp is below 32 degrees) - but have the heater come on at midnight - 3:00 am and go off at 7:00 or 8:00 am this time of year. We only supplement the GH until we get the produce from the plants we want - then shut the GH down for the winter (usually the end of October). We have not had to supplement heat yet - which is unusual for this time of year - we still haven't had our first fall frost!! We have not found an affordable method (although Cole_Robbie's wood burning stove appears to be a great option) to heat the GH from November-March. Please let us know if you come up with one!

One kilogram of water holds 1.16 watt-hours of heat energy per degree difference in Celsius. That tells you nothing about how fast that heat will be released though, just how much heat energy the water can store when it's at its warmest point. So for example, if the daytime and nighttime temperatures are 30 and 10 degrees Celsius, 1 kilogram of water should be able to hold 2.32 watt-hours of heat that it can release later. That assumes that the water is actually able to heat up to 30 degrees Celsius. If you have a lot of water in there, the temperature of the water may never be able to rise to the ambient temperature inside the greenhouse. The other issue is that as the inside of the greenhouse begins to cool, the water is already going to be releasing energy even when you don't need it. Suppose the temperature inside the greenhouse reaches 32 C and then is wanting to cool down to 25 C. The water is already going to be releasing heat during that time to prevent the inside of the greenhouse from going down to 26. Now suppose the temperature of the water has reached 25 and the temperature inside the greenhouse is reaching towards 17.5 C. The water is still going to be trying to keep the temperature inside the greenhouse from going down to 17.5. That is heat energy that's not going to be there much later in the night when it could be going down to 2 degrees. Depending on the rate of heat transfer, it might not flatten out daytime-nighttime temperatures as much as delay the temperature drop by two or three hours. That might mean if it has dropped down to 3 degrees C by 11pm, the warmest the water is going to be able to keep the greenhouse by 2am (the coldest part of the night) is 3 degrees.

At the rate and level you use a propane heater, it may not have the same effect on your plants... it may not be enough to affect anything... it may be that certain plants aren't as adversely affected by the exhaust, either. I'm not really sure. I just remember very clearly all the poor Poinsettias dropping wrinkled, yellowed leaves... some of the plants wilting and dying... it was quite a loss. I think if you're circulating a little fresh air into the mix, you will avoid any possibility of bad effects. Good air circulation is important for enclosed growing spaces, so it's something we do commonly, anyway. I'm so glad to hear you are getting some relief from cortisone shots! That's great news! :-) My husband went through the cortisone shots decades ago, when they first were trying to treat his damaged spine. They worked on a temporary basis, but the damage is too great, I think. He's been through every treatment there is, except actual surgery... which we refuse to go through. There are no guarantees he would come through any surgery without becoming completely paralyzed, and we're just not willing to take the chance, until he already is paralyzed. At that point, we have nothing to lose by trying. Of all the people we know who have gone under the knife for back problems... and that includes quite a few people... not one has gotten the results they expected, and a few are worse for having had surgery. We don't like the odds. And we can't afford the best surgeons or the best treatments, so we're kind of stuck. The last treatments he had were some steroid injections, which seem to have given him more range of motion in his neck, which is a good thing... but his back is about the same. It's trashed. I'm in better shape than he is... but we're both what we call "semi-crippled", or actually semi-disabled. Oh, well... what can you do? We just roll with the punches... life goes on! Josh, there may be some greenhouse pictures in my 2011 photo album. If you scroll through the pages, I think you'll come across a few pictures. It's nothing spectacular... just a small 10'x12' Harbor Freight special. We got it on sale, and had a carpenter friend put it up for us. It's not heated, so I only use it through 3 seasons, then I empty it out. I linked the album below, if you want to take a peek, though. African Violets are so pretty, but I haven't had much luck growing them. They always seem to die on me. I'm very lucky to get the few orchids I have to stay alive and limp along! In fact, I freaked myself out earlier... I went to mist the Phal I recently transplanted into a new pot... it was dying in the moss the grower had it in... and I noticed that the tiny little Dendrobium keiki that Chaz sent me several years ago is throwing up its very first buds!!! It's the first or second picture on the first page of my 2011 photo album. I'm so stoked!! I actually kept it alive, and it's decided to gift me with blooms! I couldn't be happier! See? This is one of those wonderful moments in life that I would have missed if I hadn't been taking my time, looking carefully at all my plants... it's just amazing! :-) I hope I didn't jinx it into dropping its buds! ;-) Oh, anyway... I'm thrilled you are getting a light setup and growing Gesneriads... that's so cool! :-) And you now have a nice spot to enjoy Hippi blooms, too! Whew! What a day it's been! I'm exhausted, but so happy! :-) Here is a link that might be useful: 2011 Photo Album

Christy, I use a greenhouse (180 square feet) for starting plants. It has a furnace that is turned on in early March. It is actually a "sunshed" so it has an insulated roof and north wall - frame construction. The south wall slopes. The angle was determined to best catch a very low, winter sun but I've never run the furnace to grow plants during the winter months. Besides the winter cold, I have to realize that the angle of the sun is very low here, there aren't many hours of daylight, and there's more cloud cover than somewhere like Colorado. Summer months the last few years, I have had basil in the greenhouse and I kept several tomato plants in there last year. Everything was opened up and it didn't get terribly hot. Basil likes it in there and the tomatoes did fine. The fruit especially, couldn't have been better-looking with no sun-damage or cracking. I think that any protection that you could give tomatoes, would benefit them. Of course, you can't cook them! However, you can get yourself into a lot of bother with a greenhouse. I have very little automation and during those cold, windy, late winter/early spring days with the big clouds and frequent sunbreaks -- I almost can't leave! The temperature goes up and drops with amazing rapidity! For the summer, the more open your greenhouse is during the daytime, the better. However, wind can be a serious problem. Of course, my tomatoes are in the open garden but the primary concern I have in selecting varieties is earliness of harvest. Even some varieties rated at 75 days have been very disappointing. Usually not but this days-to-maturity rating is sometimes really off! It should be good for comparison purposes but even that doesn't always work. Anyway, cherry tomatoes usually ripen quicker than the beefsteaks. Smaller plants, usually have ripe fruit earlier than large plants. None of this is always true but there are some very nice tomato varieties that may do well for you and be a pleasure to have on your table - be sure to give them a try. Steve