# Insulated raised bed?



## wy_white_wolf (Oct 14, 2004)

When I build one of my raised beds I made it about 8" taller than I wanted the soil level. This allows me to cover it with clear plastic and use as a cold frame. While it works it does lose most of it's heat at night. The only reason my tomatoes didn't freeze last night was because we filled about 2 dozen 1 gallon jugs with hot water to hold them though the night. 

This got me thinking. How would one go about building an insulated raised bed?

Do you think if I build one using 2" foam board that was stucco'd over would it hold up? Would a layer of foam board on the inside of a wood frame last?

Any Ideas on what might work in building one?


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## fishhead (Jul 19, 2006)

Blue foam lasts a very long time if you keep it out of the sun and protected it from physical damage like shovels. It's used underground for basement insulation.

You can also coat it with facing cement to protect it.

Maybe the solution is to put a cover over it during the day to warm the soil up to the max as well as covering it on cold nights.


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## wy_white_wolf (Oct 14, 2004)

I try to keep it covered during the day. Today's high is suppose to be 65-70. Without venting it would easily reach 100.

I'm actually thinking about my next bed and how to make it better.


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## PulpFaction (Jul 23, 2009)

I remember reading an article about a small farming operation (CSA) in Barrow, Alaska that utilized insulated beds. They just built out the beds with styrofoam and foam board, even in the greenhouses. I think you would do fine with just the foam board, maybe line it with heavy landscaping fabric or heavy mil plastic to protect it a little and that way you can also more easily shovel out your soil and add to the foam board or remove some of it to adjust things from one season to the next as you go along.


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## kyweaver (Nov 30, 2009)

Doesn't someone on here use strawbales for raised beds? That would give you lots of insulation.


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## uncle Will in In. (May 11, 2002)

If the top is covered with plastic at night, most of the heat goes right out through it. If you could lay a sheet of insulation board over them at night it would make big difference in heat loss.


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## Pennsyltucky (Oct 8, 2009)

Here's what I envision. Two 2x6's as siding for the beds nailed to sunken posts for support. Secure 2" foam board to the inside of the framing and line with either OSB lined with plastic or stucco. If you go with the stucco, I think you may need a textured surface to make it stick. Maybe you could staple some chicken wire to the board and then stucco over that. Regardless of what you use, I really like the idea of insulated beds. My only concern is delayed heating in the spring. I imagine you could overcome this by doing as you said. Fill the beds to with 4-6" or so of the top and cover with clear plastic in the spring to create a greenhouse effect and accelerate soil heating. You may even accelerate heating by tightly covering the soil with black plastic in addition to covering the top with clear plastic.


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## mellowguy (Jul 8, 2009)

uncle Will in In. said:


> If the top is covered with plastic at night, most of the heat goes right out through it. If you could lay a sheet of insulation board over them at night it would make big difference in heat loss.


That's exactly right. You could insulate the sides with R100, the heat would still escape by the easiest route, which is the top, where you have no insulation over an area that is several times bigger than the sides.Even a blanket or a sheet of plywood over the plastic would make a difference, but a 1" or 2" sheet of insulation board would make a huge difference.


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