Your real problem is that unless you are planning to insulate the living H out of it, you are looking to heat what is in essence, just a very large tent. There are any number of options and it can be done, but beyond the cost of the heater itself, you should also consider the cost of the fuel or electrical power to operate it. If you want to operate a heated GH in winter, even in Z-6; to maintain a steady 50 deg. interior temp. 24/7, you might want to reconsider either the size and/or type of GH you plan to erect, or expect to spend a whole bunch of money to run the heater.

I have a central boiler with a maximum 500,000 BTUs. The firebox is 5'x4'x3' and the 400 gallons of water surround the firebox. I am only heating the ghs with this stove. I am in zone 3 and the coldest morning of the winter is often near -30 and only rarely -40, but I am quite sheltered from the wind and we usually have enough snow for some insulation around the bottom. Yes, I have poly on both the inside and outside of 4" walls. A 30'x30' pyramid is 900 square feet and the cubic feet is found by multiplying 1/3 of the 20 ft. height. So the volumn of air is much less than a building with vertical sides. The 51,000 BTU figure is something I can work with. I'll see what the 8' finned tubes are rated at or what a plentum in a furnace blower is. A was going to try the first one with manual ball valves with a bypass and the second one I was going to try to make it thermostatic and automaticly controlled with a pump or zone valve.

OFG, those links never contained answers. A couple of years ago, we generated a list of questions to be added to the FAQ. Answers from members of the forum were to be submitted to OrchidDude, the Keeper of the FAQ. There were only a couple of us who submitted any answers. I recused myself from those two, based on the fact that 1) I built my GH from a kit, and 2) I was quite vocal that winter in our annual vented/unvented heater debate and I didn't think I could be viewed as objective. Now would be a good time to ask for answers to those and any other GH FAQ questions that you might have. Submit Q&A to OD. SB

Suzuchan, I grow my trees inside a greenhouse, and no I don't light my trees 24/7. Citrus trees, in fact all trees, use sunlight, carbon dioxide from the air, and water from the roots to produce carbohydrates (sugars/starch) during the day light period. Then at night, the tree breaks down the carbohydrates that were manufactured from the previous days buildup, and metabolizes (uses) the sugars as their food source (energy). Therefore, citrus trees require dark periods to do this. Interestingly, no matter how long, or short the dark period is, the tree will always consume 95 percent of the sugars produced the preceding day. For example, when equal day and night periods exist (12 hours each), the tree will use up 95 percent of the carbonates made the previous day and leave 5 percent unused. The same will be true on a 8 hour day and 16 hour night, the tree will still only use up 95 percent of the previous days carbohydrates and leave 5 percent unused. With in reason, no matter what the daylight/dark ratio is this equation will remain the same, always 95 percent and 5 percent. I light my trees from dusk to 10:00PM every night during the winter months. Doing so produces more tree growth, thus more fruit. - Silica