Green House Floor Insulation?

I am planning on a greenhouse purchase and live at 6000' in Montana and want to insulate the floor. This would be a hobby greenhouse. Does anyone have an idea of a good way to insulate the floor?

Hello Marcia,

I've got some past experience with greenhouses at the commercial level.

First, I would say that you really DON'T want to insulate the floor of a greenhouse!!!
Think of the floor as a potential heat sink (heat storage) that will collect heat during the day and release it at night.

But I understand your question. Though I don't have experience at that elevation (6000ft), I realize your issue as you have cold nights and probably very cold winters and you want to capture and retain as much thermal energy the sun will provide.

There are some interesting ideas that could be utilized on larger greenhouses (those with a better ratio of floor square footage to the interior volume within the greenhouse). But I don't think those ideas or methods make sense (cost is high & affect is minimal) for a hobby greenhouse.

But never the less, there are some things you can do!!! For the floor treatment I would recommend first a layer 3-4" of crushed rock as the floor (for drainage). Then cover that with black ground cloth/plastic (to help absorb the the heat). Not sure if you will be growing on the floor or will be utilizing benches, but the black covering on the floor will help with trapping heat into the floor.

Aside from the floor, if you plan to have some sort of bench system in the GH, you also can utilize 55gal drums (also painted black) filled with water. Realize that the drums of water take up precious space in a GH, but could work well if you build your benches over the top of them! The drums of water will retain heat as well.

Another suggestion I can offer to you is dependent on how your GH will be constructed. The suggestion is to vertically line the perimeter of the GH with 2" thick Styrofoam. 2" thick and 2ft deep from the floor level down. Another similar method would be to provide a concrete foundation (2ft deep) for the GH to sit upon. Either will help your floor to retain more of the heat it absorbs. Some heat will escape the floor heat sink along the perimeter of the GH otherwise.

Other insulating ideas:
1) Dbl layer poly covering (inflated).
2) Styrofoam or other insulating materials used around the perimeter above the ground on the sidewalls and endwalls.
3) Or better still, a GH that is oriented east & west (the length of the GH) and then totally insulate the north wall. A GH that is oriented this way captures more light and heat than any other configuration.

Hope that helps!!!

---Dave

Marci

I live south of you in the Gallatin Valley. My greenhouse is not double walled and leaks like a sieve so I have not tryed to keep plants growing in it all winter. Other people do though. I have not heard them speak of insulating the floors, they plant in the floor. What these greenhouses have is a double film that has a fan that keeps the walls inflated, thus insulating a lot. Black barrels filled with water with boards across make great dual function plant benches. Planting in the floor for the winter are covered also with a thin floating row cover.



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