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Old 01-08-2017, 08:40 PM
GpsFrontier GpsFrontier is offline
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Join Date: Mar 2009
Location: Lake Havasu AZ.
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Hello shillamus,
Thank you for the link. It's similar in concept to other greenhouses I'm familiar with, however I haven't seen a greenhouse quite like that yet where the entire greenhouse except the roof is underground. At 13,000-14,000 feet it can get very cold especially at night. The ground is a great insulator. I agree there are many areas where ground water would be a major problem, including areas with permafrost. So it really depends on the location.

I live in Arizona and the summer heat is my biggest problem. The ground gives good cooling and I do have plans to build something similar. Just not so deep. It's fairly common for greenhouses to be partially underground. That helps it keep cool during summer, and insulate it during winter. But still allows light through the sidewalls. The double wall greenhouse glazing has a air pocket that circulated air between the layers to insulate while allowing light through. The same way double pain glass windows insulate your house from outside temps.

I attached some drawings of the greenhouse I plan to build. It will be dug in 2-3 feet deep. That will give good cooling while still letting in lots of light to he plants. It will also have double wall greenhouse glazing to insulate the top as much as possible. I also plan to build a subterranean cooling system to replace air conditioning.

With any greenhouse you need water drainage, and with a dug in greenhouse water drainage can be a problem. But there are a few ways to work it out. You don't ant to just have a dirt floor because you will be trammeling around in mud. Using a 4-6 inch layer of crushed rock will allow water to drain while keeping you above the mud. However if you need a more solid floor you could build a composite decking floor above the crushed rock. That will allow water to drain through the slats, but give you solid footing. Composite decking is more expensive than pressure treated wood, but it's more durable, wont absorb water, and is maintenance free. If it's a large greenhouse, building composite deck floor would be very expensive. So if you don't want to use crushed rock, a cement floor would be much cheaper than a deck floor. But cement wont allow water to pass through, in which case you could build a sump pump system like they use in basements.

Also in many cold areas people will build a dug in greenhouse that's attached to the house on the side facing the sun. The house provides insulation along that wall while the greenhouse absorbs the sun's heat through the greenhouse glazing. I attached a simple drawing of one of these too.
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