I am considering locations on my property for a small temporary greenhouse (for example, some variation of this greenhouse.

A great place for Sun exposure is my South-facing porch, which is wooden and sits a few feet off the ground. The primary use of this greenhouse will be starting tomatoes/peppers as early as possible.

Will the fact that the greenhouse is off the ground mean that it won't hold heat as well, and won't be as warm as a greenhouse on on the ground? If so, is there a simple way to insulate it?

1 Answer 1


Actually it'll be quite the opposite: with the cooling effect of the ground gone (it's strong enough to keep heat pumps working!) your greenhouse will get a lot hotter. In fact you'll probably need to find a way to prevent your plants from overheating/getting cooked in that greenhouse after a while. My recommendation would be to ensure that it can be as well-ventilated as possible.

  • Notice the primary use is early starting of plants - my understanding is that while the air temperature varies, the ground will gradually warm. Once the ground is thawed, the temperature in the greenhouse will generally remain above freezing. But if the bottom is open to the air (under the deck), won't the air in the greenhouse just follow the varying air temperature outside?
    – cduston
    Jan 9, 2021 at 1:43
  • 2
    Potentially very hot in the day but dropping to air temperature at night. One thing that is done is add large containers of water ; they heat during day and provide some heat at night -" thermal inertia ". Jan 9, 2021 at 1:44
  • @cduston Actually the air warms and cools much more rapidly than ground does (it's simple physics - the heat capacity of soil, particularly wet soil is several order of magnitudes larger than that of air). This means that without the thermal inertia of the ground the temperatures would get more extreme (a lot hotter during the day and a lot colder during the night) which you might have a harder time controlling. Yes, the air in the greenhouse will track the outside temperature, but only to an extent. And on a frosty night the greenhouse could get below freezing point quite fast too.
    – CoolKoon
    Jan 11, 2021 at 18:36
  • @CoolKoon, giving your tone some flexibility here, you've verified the concerns of my original comment. I'm worried about how cold the greenhouse gets at night. For sure heating during the day from the Sun might be an issue, but the ground is a thermal stabilizer in both situations. I'm concerned about removing it, which will make the greenhouse track the air temperature more closely. For sure, hot temperatures during the day might be an issue, but it's a little hard to imagine a 100 degree greenhouse on a 50 degree day (details matter of course).
    – cduston
    Jan 13, 2021 at 15:04
  • @blacksmith37: Yeah I've heard of using something like water with a high heat capacity - good idea.
    – cduston
    Jan 13, 2021 at 15:05

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