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Foundation insulation on greenhouse with external planting beds

16 years ago

I have never had a greenhouse before so I look forward to your suggestions. I did read the FAQs and search the threads before writing this. I received a GH kit for Christmas from my DH. Since we have no level locations available for the GH, we are currently planning on building a foundation wall from 8x8x16 cinder (cement) blocks. At the north east end of the GH the top of the foundation will be 2 blocks above ground level, at the southwest end it will be 3 blocks above ground level with at least 4 inches underground as a footing. The floor inside will be more level but not cement.

Since we live in a moderately high desert valley, the summer days are hot (>105 F) and the winter nights get cold (9 - 15 F) but with days normally above freezing, I am planning on also using the cinder blocks to build 2 foot wide raised beds along the south and north sides of the GH that will each share a wall with the GH foundation. The result, from an outside view, will be a rectangle the length of the GH with a width over 5 feet wider than the GH. In addition to hardware cloth under this rectangle to keep out the pesky gophers, the rectangle will be surrounded by a two-foot wide border of cement pavers.

I am planning on planting heat-loving vines on a trellis in the south side planter of the GH in the summer and shade-tolerant plants on the north side. In the winter, the north bed will probably be covered by insulation panels and the south bed will have a hoop row cover.

I am hoping that it will be possible to use the ground under both the planters and the GH as a heat sink. (Something like a "raised pit GH" ;-) ) Not counting the insulation added to the GH itself, there will be insulation for the ground and foundation.

Does the idea of expanding the ground heatsink out under the planters make sense?

Since our ground does not freeze very far down, would putting insulation horizontally under the outside paving be sufficient or will there need to be a vertical insulation barrier as well? If so, should this vertical insulation barrier be at the outside edge of the paving or at the outside edge of the planters and greenhouse?

I am planning on filling the cement blocks on the outside of the planters with perlite with some gravel or crushed rock at the top to keep it from blowing away. The foundation wall of the GH itself will have the blocks filled with cement mixed with perlite. For the end walls of the GH, I will add insulation to the inside. Will this be enough insulation for the foundation and planter walls or do you think I will need to add additional insulation panels to the planter walls? If you think that additional panels will be needed, should the panels be on the outside or inside of the planters? If it is on the outside, then I can add or remove it as necessary. If it is on the inside, then it will need to be permanent since I am hoping to not have to empty the planters twice a year.

I would like to get the foundation right the first time since the foundation walls under the GH itself will be permanent due to both cement and rebar. Any answers, suggestions, corrections, etc. will be most welcome.



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