Monday, February 18, 2013

32 outside/ 80 inside

I did a bit more to insulate over the weekend.  I now have 2 full layers of greenhouse film separated by 4".  One is stapled to outside of 2x4 frame and the other layer stapled to the inside.  All seams are fully taped on the outside, but I have yet to tape the seams on the inside layer.

I also finished the Reflectix bubble layer on the north side.  There are still some odds and ends to fix for air-tighness:  the door does not seal well as I need to plane down one side, the greenhouse fan needs to come out and that area needs glazing, and the bottom of the base wall will be sealed with the addition of flower beds.

Today was one of those days without a cloud in the sky.  The temperature never got above freezing, but at 1:30, after 5 hours of full sun, the greenhouse is 80 degrees.  I am quite pleased.

In order to provide better data on the temps, I will need some better equipment that I can make graphs from.  I would also like to start measuring the pond temperature to see how it fluctuates during the day.


  1. Nice. Now it's time to start blowing that hot air underground to warm up the grow zones.

  2. It's blowing every time the sun is out. I need to buy another 10-foot tube and bury what is currently exposed, but the sub system is working great.

  3. I am in the process of building a dome very similar to yours. I am in SC on the Georgia/NC border so I am in a mountainous area with pretty mild winters. But I am really curious about your heating system. I am building a 22 foot 3V 5/9 dome and the winter heat issue has been one I am most concerned with. I really don't want to waste space with a rocket mass heater and really think your idea is great. I am doing an aquaponics greenhouse.

    Ok so my question is this are the pipes drawing in the heated air to the underground the only source of heat you are using?

  4. The short answer is yes. The insulation boards in the ground around the perimeter, the sub air circulation and the pond itself are all working together, not to heat, but to maintain as much heat through the night or until the sun heats it up again. The pond hasn't seen any ice, even after 3 consecutive nights of single digit lows, but there's no way tilapia would be happy in that water.

    1. That is really cool. To be honest I haven't seen a single digit night here in about fifteen years. I plan on having bream since I know that tilapia need warmer water to live. I really thing that your system - which I have not seen anywhere - would keep my place warm enough for year round growing. Also, how did you overcome the uneven base on your dome? You did a 3v right?

  5. I think that with enough insulation and multi-wall glazing, you would be happy with the extra heat from the sub system. If you want to play it really safe, add more tubes below the center of the floor.
    As for the uneven base, I had to pull really hard and sacrifice some accuracy in the joints. I was unaware of the Kruschke Method for achieving a flat base. Look on for all the info on this. It seems that no matter how much research you do, you always miss something!

  6. Hi, I just stumbled over your blog while searching for information on geodesic dome greenhouses. Thank you for taking the time to share your experiences. It's very useful as I'm planning on building my own once I've retired from my current job.

  7. Glad you like it. Good luck, and remember to build it as BIG as you possibly can!