greenhouse wood heat

[deng43]

i am sure this has been answered, but i cannot find it- sorry. have just put up a 16x20' bc greenhouse

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and i would like to link it into the wood furnace that is in tandem with an oil boiler in the basement. the house is pex from a manifold to two heating zones, hydronics, but i would like to heat the g.h. with pex only. is this possible? i am not a whiz at this and tho i know how my hot water heating system works it still mystifies me at times. i can visualize the hydronics in the greenhouse and see how it would heat fine, but i would really like just one pex loop that was not so subject to freezing and bursting. the pex could just be in a big loop de loop on the g.h. floor gravel and i could put duck boards over it for walking.

freezing and burst copper has happened in the house twice and is fairly awful. how much pex would i need, say 1" coiled, to heat this greenhouse to about 45 f? we are in maine and it gets down to 0 f, or a bit less, now and then, but we spend a lot of time in the teens and twenties. basically i just don't want to get a freeze in the greenshouse. we are looking to have winter veggies. i really don't know how well the two-wall polycarb does r value-wise. thought i would insulate the bottom two feet and north wall with 1" silver back foam. i don't mind if the system runs a lot of the time; my wood boiler tends to overheat and put itself out if i don't keep the fire restricted. my thought was that i could just put a circulating pump on the output of the wood boiler and run it to the g.h. in a trench. the trench will be about 40'. there is already such a set up on the wood boiler output that kicks in to divert hot water to one of my house zones when the furnace gets raging.

i realize this question is rather broad, but a good estimate from someone who may have done this in a similar climate would be appreciated. oh, i will be growing in 2' deep cedar boxes set up off the gravel on 4x4's. at some point there will also be a 2 person japanese soaking hot tub in the greenhouse; this will add a bit of heat also. i am thinking of building a tub from cedar and hooking pex to it and keeping it at about 102 f. thanks for listening. don e.
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[Willman]

Hi, I don't know where you are in Maine.If you are near Paris you can check out the greenhouse that is set up at the extension office there. It isn't a year round house. Barbara is the lead person on the project. (cut flowers) Others are in Bangor area. They have a solar heat set up with a large storage tank infloor with tubing circulating HW under the beds. Planting starts in early April and goes into late Oct. using solar only.
The extension service has a lot of info as well as experts to work with you in your endeavor.Give them a call.

I was impressed with the in gound beds versus bench planting. Plants like warm feet too. Short plantings could be tented to conserve heat in dead of winter. Remember to insulate the heck out of the ground below your beds.
Will

 

[Willman]

i really don’t know how well the two-wall polycarb does r value-wise.

The house in Paris is double skin that is kept inflated, much better performance as well as stronger.
Will

 

[deng43]

will, thanks. called them- i am in auburn, and will go over today. had to laugh as i did a google on 'paris maine greenhouse extension' and your reply to me was on the first page of results. damn, those people are fast. don e.

 

[deng43]

tlked to barbara at the extension g.h. she straightened out some of my thinking:

there isn't enough sunlight to grow all year round here

the most important thing is to heat the root zone; the air only need be above freezing.

the most important resource is eliot coleman's '4-season harvest'.

don e.

 

[Willman]

Ayuh.
I have a insulated cold frame which I grew greens all winter without supplemental heat. Started plants in Oct. and went till a hot and then cold snap in feb while I was at work froze everything. Shoveled off the snow every storm. Used foam board and a sleeping bag at night for insulation on glass. Will do some other ones this fall.
Will