Radiant Floor Heat Greenhouse

cre10March 29, 2013

I've been wanting to build a 30x60 greenhouse with radiant in floor heat. I want pex tubes in the plant beds so I'm not wasting heat. I've had a few different ideas

Pour concrete plant beds with pex in them to heat, but I'm worried about the cost and bulk/weight of the beds. These would be like the concrete feed bunkers for cattle.

Pour a insulated concrete floor with pex in it and put dirt on top of the concrete. My worries here are floor drains and expense of concrete?

Put pex directly in the dirt floor. This worries me because the pex is not protected, if I insulate the floor then I don't know how long it would last being directly in dirt. Without insulation then I would be heating a lot more soil mass than necessary.

The greenhouse would be poured like an earth contact home or walkout basement to help keep it warmer and then the top of the greenhouse roof would start about 1 foot above ground at the soffits.

Has anyone done something like this? Any tips or advice?

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I plan on using spray foam insulation for the sidewalls of the interior foundation. The hot water for the pex lines will come from a water to water geothermal heat pump. I'm just torn what to do with the floor and plant beds.

    Bookmark   March 29, 2013 at 12:45PM
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I think it would make the most sense to heat the concrete slab floor just like it were any other type of building. Then you can grow in raised beds or containers. Heating the slab will help it maintain a constant air temperature as nighttime temps drop, which is what you want.

    Bookmark   March 29, 2013 at 9:27PM
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You might want to put the insulation on the outside of the foundation walls. That way the concrete's thermal mass can work for you, and you wan't have to protect that foam.

    Bookmark   March 30, 2013 at 5:50PM
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What do you guys think of dirt on top of the slab and growing on it?

    Bookmark   April 1, 2013 at 12:18PM
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I think its bad idea, you need to clean time to times for reducing heat loss on heating the soil layer on your slab. Make sure you properly install PEX in slab.

Here is a link that might be useful: how to install pex tubing in slab

    Bookmark   January 7, 2015 at 4:06PM
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