Oh and I guess I should mention that idk if its the humidity hurting the plants as much as the fact that my soils stay saturated and I haven't watered in weeks. Most of my plants are in pots using Al's mixes, whiched worked wonderfully this summer. I also have a few raised beds, which I got recipes for off the sq. ft. gardening mixed with used Al's 5-1-1 to improve drainage, and these seem to being doing the worst.

We have also been experiencing a wet and cold winter so far adding to my dilemma. I just don't think I can ventilate much more at this time because I don't have any automatic systems to do it when it can really utilize it. I also have a huge white pine that blocks afternoon sun form dec. til mid jan. which I thought would help keep it from overheating while I was at work, but I think thats hurting me now.

So many factors in play I think I may have to give up for a month or 2 til I can get more sun. Its that or buy a new thermostat controlled gas heater, get automatic venting system, and a covert tree topper to take care of the neighbors tree!lol

My thought is just grow what you can at much lower nighttime temperatures. Your heating bill at 34F will be a small fraction of 60F. Cooler nights won't completely cure the humidity problems but electric heat and cooler might help.

If you want to stay with propane you could go to a hot water heater, radiator and fan. Or use pipe (like floor heaters) below the plants giving off radiant heat supplied by the hot water. The hot water heater should either be outside the green house or enclosed with combustion air and all spent fuel gas coming or going to outside.

Thanks for the help. The main reason I had decided to keep the gh growing was b/c I got a dwarf musa cavendish this summer and I have to keep it from going dormant if I ever want bananas. I can't keep it in the house b/c I have no southern facing windows and sectioning the greenhouse didn't seem feasable to me. Of course after I got the banana I learned there is a cold hardy one, but I also thought it would be great to have vegies in the winter.

The water heater is a great idea but I don't wanna buy one. I'm not sure if I would have the same results with the water heater b/c it would seem to me that heating water would be less efficient than heating air. I've just been really pleased with the propane heater b/c it cost about the same as the elec did last year but keeps it above 50, whereas the elec only kept it 10-15 higher than outside which isn't enuf for much if it happens to drop to single digits as it does a couple nights a year. So actually my heating bill for 34 was about the same as it is now at 60. But it isn't as cold yet as it was last year.

Maybe there is a way to trap the moisture produced by my heater? Maybe a sloped pipe with cold air circulating thru for the water to condensate on and then run down the pipe. Idk something along those lines. I've been thinking alot about going to wood next year, I just don't like the idea of it being in such a small plastic tunnel and it can't be regulated as easily.

A dehumidifier would help but you may be costing yourself a lot more money. The water would condensate on the cold surface but at the same time remove heat from the air.

All energy put into dehumidifier stays in GH air. In fact I use my dehumidifier to heat my GH on mild days while I am dehumidifying (I turn off the heaters).

When the temp is in the 50's I open the door and blow in fresh air to get rid of humidity and oxygen rich air. I am getting more tomatoes this winter than I got during the summer. I have the 13'X7' GH totally insullated with a 16 mil bubble pool cover and can keep the min temp at 60F when exterior temp is in low teens using a 1500 watt electrical heater.