book collections email follower instructable user

Step 9: Final Thoughts

Picture of Final Thoughts

With a single 1500 watt, 120 volt heater I can maintain a 20 degree F differential to outside temperatures throughout the winter. It takes 14000 BTUs to reliably provide the 40 degree differential required by our coldest days most years, including losses due to safety venting. If I were to better insulate the bottom portions of the structure and the north wall, as originally planned, and switch all of my heating to electricity, as still planned (hydroelectric is cheaper than gas here, even for heating) I could certainly realize greater economies of heating.

The original plan was to run as much as a 65 degree differential, with 30000 BTUs of available heating, and I may work toward that when I replace the cover again this next year. I do maintain ponds, aquariums, and fresh water storage totaling about 1000 gallons in the greenhouse, which provides some thermal ballast. I have no idea how much, since they have been present since before I sealed the structure.

For a while I had installed low pressure misters on the second tier ring (~7' up) around half the greenhouse. These provided 15-20 degrees of cooling when run 5 minutes at 20 minute intervals during our 115 degree weather, keeping things below 100F. Unfortunately, they clogged easily and were difficult to fix without replacing all of the emitters, even when I placed multiple filters on the inline. A high pressure system would probably work better, with a booster pump

I've mostly kept a bare floor, with various types of rock or rubber mats in places. I know this is unusual, but it works for me. If you want a fancier floor, it should be similar to installing such in any greenhouse.


  • Basic Frame - $700
  • Glazing in and out - $300
  • Other parts added - $600

I would add 50% to these costs today, mostly to account for greatly increased transportation expenses (which gets bundled into the price of goods as well as direct shipping), but also inflation.

Frame costs are mostly dependent on the price of lumber.

Quality glazing always represents a significant cost, and I think the amount listed is lower than usual. Unfortunately, poly film is only rated for four years and has to be repurchased and installed. Although I've replaced the internal plastic twice in 12 years, I highly recommend the woven external material for its strength, ease of handling, durability, and scattering light transmission. I'll be replacing it this year for the first time.

Other parts' cost will be higher or lower depending on choice of door, vents, heating and cooling system, etc. This number probably has little relation to the type of greenhouse constructed, and is probably least informative for someone trying to construct a similar structure.

LarryF293 months ago
Probably a very nice project but after the first few paragraphs I deceit was too confusing to follow. Angles and descriptions confusing for me to follow.