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Heating a 7000 sf Greenhouse in AK


Joined: Aug 13, 2009
Posts: 10
So, there's a place for rent in Wasilla, AK that is 7000 sf fiberglass greenhouse with the plastic insulating liner, natural gas heat.

I'm trying to put together a business plan to get it up and producing food for a number of restaurants and families in the town I live in, but everyone is balking at the "unknown" utility costs of the operation.

The greenhouse was a foreclosure and the current owner has only vague numbers for the heating costs, approximately $1000 per month AVERAGE for the 2007 year, which suggests to me that they were obviously not using it year round. (I think the former owner focused on roses and shrubs and the like.)

What would you do to renovate such a building into a more sustainable model for alternative heating in a year-round food producing greenhouse?

I'm taking all considerations from solar options (good about 5 months of the years,) to heating with waste such as manure or wood pellets or what have you. I'm also working with someone that may be able to get us going with some grants to experiment in heating with methane.

The property includes six acres, and some small livestock production is a possibility, so waste from that could be produced and used all on site.

Still kind of a pipe dream, but thought I would see if any of you had any valuable input.
paul wheaton

Joined: Apr 01, 2005
Posts: 17427
Location: missoula, montana (zone 4)
I am starting to put together my pics and clips for a rocket mass heater in a greenhouse to push up to youtube. 

Have you seen the video for the oehler greenhouse?

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Ernie Wisner

Joined: Oct 16, 2009
Posts: 789
Location: Tonasket washington
Ahh you got to love FG houses. what kind of night covers did they use?

I am betting that a 7000 sq ft house had no covers. so IMO you got a couple ways to do it. heat the beds so there own thermal mass is what holds the heat through the night, divide the house so you only heat the section you can afford to heat. this makes it nice cause as you make more money and need more space you can just open a section up. it also lets you have gradents so you can have lettuce growing in a cool to cold section while you have mungbeans and tomatoes  in your hot section. hope this helped

Need more info?
Ernie and Erica
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Kathleen Sanderson

Joined: Feb 28, 2009
Posts: 985
Location: Near Klamath Falls, Oregon
Ernie's idea is a good one, to zone the greenhouse.  We had friends in Tok who had a small greenhouse (maybe thirty feet long or so) and they had a wood stove in the center section where they grew things like sweet potatoes, tomatoes, and peppers.  Then the two end sections were used for things that could take cooler temperatures.  I don't think they were growing year-round in it, but maybe you could in Wasilla. 

I would think you should look at a combination of ways to heat the greenhouse.  You wouldn't likely be able to heat it completely with just one thing, like solar or wood or methane or a compost pile.  But maybe with all of them together (especially use some rocket stoves and run the flues through the growing beds), plus some extra mass and night covers, it would be feasible.  I don't think you'd be able to grow warm weather stuff in the winter, but you should be able to keep it warm enough for cool-season greens.

You also should grow seedlings for people -- you could do custom grow-outs.  A lot of the greenhouses around here make most of their money that way.  Lettuce and salad greens are also big sellers and are high-value crops, and don't need a lot of heat.

Ken Peavey

Joined: Dec 21, 2009
Posts: 2523
Location: FL
Energy efficiency strikes me as being of great importance in an Alaskan greenhouse.  With the long cold nights, heat and lighting are the targets.

The north side of the greenhouse would offer little light gain for all the exposure.  Building and insulating a solid north wall.  An inexpensive option may  be to stack hay/straw bales to cover the north wall.

If zones for the greenhouse is your plan, the east and west walls could also be blocked with hay/straw bales.  These walls get more sun than the north side, but whether they lose more heat than they allow in would need to be looked at.

The roof, even with a dead air pocket will also be a leader in heat loss.  Consider adding a reflective curtain.  Roll it out at night.  Extend it to cover all walls at night.  This would help contain heat as well as light.

Lighting in an area with 4-6 hours of sun each day is going to run up the electric bill.  Planting short day crops can reduce your lighting demand to 12-14 hours/day, but this is sunlight demand.  Substituting florescent lighting for the sun, 6-10 hours/day will take some doing.  Shade tolerant crops can reduce your lighting need. From there, look for the most energy efficient lighting, but it still has to mimic natural sunlight.

Seed the Mind, Harvest Ideas.
Ernie Wisner

Joined: Oct 16, 2009
Posts: 789
Location: Tonasket washington
another way to reduce power use and increase natural light is mirrors. Mirrors on the N side would be able to reflect lots of light back into the space. this would result in You needing fewer light fixtures to provide the amount of light lost to the north. the intensity and duration of light on plants is the key so upping the intensity and keeping a light cycle that includes day time natural light, morning and evening blending will cut your costs down quite a bit.
Joel Hollingsworth

Joined: Jul 01, 2009
Posts: 2103
Location: Oakland, CA
It seems that wood waste and manure are the way to go, probably not all via burning.

If you haven't read this paper on compost-heated greenhouses, I highly recommend it:

You might have the space for two or three big windrows with the beds directly above them, or you could build several Jean Pain-style piles and just have ductwork leading to all of them, with electronic control of where the vent fans draw from and how quickly, and to which coils, the heat-exchange water circulates.

You might also find these two blog posts interesting, from Rob over at One Straw:

Lastly, if you're heating with methane (produced on-site, or natural gas), I wonder if it's worth looking into lighting the place with limelight or with cerium-thorium gas mantles. There might even be a mantle composition that gives a better frequency mix than sunlight (not much green, perhaps).

"the qualities of these bacteria, like the heat of the sun, electricity, or the qualities of metals, are part of the storehouse of knowledge of all men.  They are manifestations of the laws of nature, free to all men and reserved exclusively to none." SCOTUS, Funk Bros. Seed Co. v. Kale Inoculant Co.

Joined: Mar 01, 2010
Posts: 3
I saw these two links about solar bubble greenhouses on the Alaska Permaculture site (it's a Ning community). The first link is to a solar bubble greenhouse in Ontario, so if one works there it should be able to stand the weather in Wasilla.

Joined: Mar 01, 2010
Posts: 3
By the way, there are some good links to Alaska-based garden resources on the Sitka Local Foods Network site, You might search the site, where there's an article on the greenhouse up at Chena Hot Springs Resort near Fairbanks. The Chena Hot Springs Resort, including the greenhouse, is powered by geothermal energy. The greenhouse is huge (grows more than 200,000 heads of lettuce a year, in addition to a half-dozen or so types of tomatoes and other veggies).
Emerson White

Joined: May 02, 2010
Posts: 1206
Location: Alaska
I wouldn't go for it. If you want to grow veggies I would look for a large wooded lot with a south facing slope, build your green house on that slope so you have tiers of greenhouse and can use the warmth of the bottom tiers to raise the temp of the upper tiers. Lining the north wall with foil faced Isocyanurate wouldn't be a bad idea in winter. Getting a hold of wood chips and the like to burn would also be a very good step.  As for a wooded lot you can cut your own wood and keep going that way. I don't know about the black spruce in the tiaga but sitka spruce has half of its heat energy in the limbs because of all the resin, and people throw them away when they cut wood because they increase the risk of chimney fires, so if you build a rocket stove (which handles creosote very well) you can possibly take advantage of that additional resource. Most of the money in firewood is in the labor needed to fell cut chop move and stack it.
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