Permaculture derived far north greenhouse

[John R]

 

I found this greenhouse on another site and thought people might find it interesting.  Even though I haven't got my first system up and running I'm already rolling expansion plans around my ever fevered mind.  One of the points brought up in this article is the difference between regions that need to harvest lots of diffuse light due to overcast conditions versus this design.  This winter it seems like I haven't had but one sunny day out of ten.  This design appeals to me as a good one for aquaponics but if the standard design is better for overcast conditions then maybe that's a better choice for me.  I'd like to know what people with greenhouses think about the choice of greenhouse type as it applies to local lighting conditions.

 

Link to the original article:

http://www.vergepermaculture.ca/blog/2011/01/09/how-we-designed-our...

 

[Kobus Jooste]

Being on a temperate lattitude, I am not that clued up about trying to harvest diffuse light.  Currently, my polycarb greenhouse hits an ambient temp of 124 degrees F with the vents open 24 hours a day and 40% shade netting installed inside. It does not even get full day sun.  Luckily it is set up for duckweed experiments and thus I can carry on through the peak of summer.  What is interesting to me is the low sloping roof.  When I built my system, the reps for the multiwall polycarb said that the product is very good at scattering light evenly throughout the structure.  Is it necessary to slope the one side down so far?  What would the difference be in terms of light penetration if it hit a vertical side wall versus that angled roof?

 

The reason I ask this is that with such a low side wall, you will have less efficient use of the greenhouse footprint from my perspective.

[John R]

 

Kobus - from what I've read, the angles are chosen to facilitate energy harvesting at low sun angles in the winter while giving it some shade in the summer.  In particular, the angle of the windows is chosen to be fully penetrated by the low winter sun and angled sharply enough to reflect a lot of light off when the sun is high.  The glazing of the glass was also chosen to facilitate this.

[Kobus Jooste]

Cool.  These considerations has never been an issue to me, thus it is always interesting to look at them and learn something.  I'm still trying to figure out what the best option is for me.  Summers are very hot, but only for 3 months, winter is quite cold, but again, only about 2 - 3 months.  The 6 months in between is awesome, and a system could be open with no heating or cooling needs.  I'm starting to lean towards open systems with moderate water heating needed in winter

[TCLynx]

Where are you building this that you are searching for "FAR NORTH" greenhouse designs?  I thought you were in Indiana?

 

However, this design might work well for winter and insulation, I don't know that you really need as much reflection of summer sun as long as you can open up the greenhouse pretty well to get air flow through in summer.

 

A benefit of this kind of design is that you could (if you will be around daily) have reflective insulation panels that you stand up against the tall windows for over night to help retain heat and then open and lay on the ground in front of the greenhouse in the morning to help reflect more light and heat into the greenhouse.

 

Keep in mind that you will probably have to do some work removing snow.  In a regular greenhouse the snow doesn't tend to stick to the vertical walls and heat escaping will tend to help melt it off the roof but that angled big window I expect will tend to build up snow along the lower half.

 

Other than those observations, I've never dealt with a greenhouse when I was living up in Michigan and here in Florida, there are only a couple months where I sometimes want a greenhouse.

[John R]

 

TCLynx - I originally found this posted to the energybulletin.net website and even though they're a full 10 degrees further north it certainly feels like the far north up here right now.  And I really like your idea about the insulating reflecting covers for the side.  That would probably be really useful for their greenhouse since they implied that it was quite dry.  Not so much for me since there's plenty of snow around here to reflect the light.

 

I'm envious of both you and Kobus with your houseless growbeds but I don't have that luxury here.  Two things that I really want to concentrate on for myself is winter vegetable production and minimizing energy consumption.  I like greenhouse designs like the one featured in that article since it minimizes the area of glass which is where the most heat is lost.  But I'm concerned that the amount of overcast here might make that type of greenhouse ineffective.  All the greenhouses I've seen in this area follow the 'european' design discussed in that article but my yard won't really accomadate that type and I've never really felt that they 'fit' well with aquaponics since the tanks seem to get in the way to a certain extent.  Perhaps supplemental LED lighting is something I should look into.

 

[Darrin Charbonneau]

John,

 

Thanks for posting this greenhouse design along with the original link. Very informative, and exactly the design I've been searching for. Most northern climate backyard greenhouses are neglected for the winter and primarily used extend the growing season. I have already sourced some free insulated garage door panels to use for the structure! (half the fun is improvising on a budget).

 

I'm planning on about 5 water barrels, and a 270 Tilapia tank for thermal mass heated an Evacuated tube system.Hopefully it will be the only heat source required. I'll know next winter...

http://en.wikipedia.org/wiki/Solar_thermal_collector#Evacuated_tube...

 

I agree that supplemental LED lighting will help during the short days of winter.

 

 

[TCLynx]

My concern with LED lighting is that it is much like florescent lighting still, as in for it to be really effective you need to have the fixtures rather close to the plants (like a couple inches from the leaves) which would mean you need lots of them and the lights themselves would block much of your limited sun light.

 

For supplemental greenhouse lighting, it might be far more effective to use a couple of the Metal Halide placed up at the peak or just inside the solid part of the greenhouse so they are not blocking sunlight when it's available and so a couple fixtures can provide supplemental light for the entire greenhouse as well as providing some heat to the greenhouse.

 

Now it seems as if the Big fixtures use more electricity but as it actually turns out for lumens per square footage of plant growing space, the big fixtures come out similar to florescent.  As in to get the same amount of light to the plants you might use one 600 watt MH fixtures place further from the plants or three 216 watt florescent fixtures right on top of the plants.  Obviously the MH fixtures are better suited to a wider variety of plants since they don't need to be placed so close.  (Really hard to grow both lettuce and a tomato plant under the same florescent fixture.)

 

Theoretically the LED fixtures will be able to be tuned to exact frequencies to deliver only what plants use but at this day in age, I doubt you can really just place a few LED fixtures at the peak and get improved plant growth from them.  Please post info about it if you know otherwise, I do realize LED fixtures are an ever changing field right now.

[Paul Letby]

Very cool that you posted this John.  I'm looking into greenhouse design for when I build mine and this one gave me fresh ideas.  I'm at 49 degrees north so this really applies!  -45 degrees C with the wind chill a few days ago tied with the coldest city on earth that day, so I really have to consider winter efficiency in whatever design I select.  Have you considered the soap bubble design?  I would imagine it could be applied to this design.  Soap bubbles are injected between two layers of plastic one foot apart to insulate to R30 at night, and on the coldest days you could still use it as it allows photoactive light to pass.  The soap solution is collected at the bottom of the glazing and sent to the sump for recirculation.

 

 

[John R]

 

I thought people here would like this, thanks for letting me know.  A friend showed me some material on the soap bubble design and it seems pretty cool but I just can't seem to get past the slimy soap factor.  But if I was that far north I'd probably find a way.  It just seems to me that over time one would have to deal with leaks, scum, etc.  But I don't think my issues are all that rational and it certainly sounds good on paper.

 

I'm certainly really concerned with heat lose too but I'm focusing more on the kind of static insulation that this type of design lends itself to plus cheap and easy 'blankets' to use over the windows.

 

Good luck with your greenhouse and please keep us informed as it progresses.  I'd like to hear more too about the bubble insulation if you decide to take it up.

Paul Letby said:

Very cool that you posted this John.  I'm looking into greenhouse design for when I build mine and this one gave me fresh ideas.  I'm at 49 degrees north so this really applies!  -45 degrees C with the wind chill a few days ago tied with the coldest city on earth that day, so I really have to consider winter efficiency in whatever design I select.  Have you considered the soap bubble design?  I would imagine it could be applied to this design.  Soap bubbles are injected between two layers of plastic one foot apart to insulate to R30 at night, and on the coldest days you could still use it as it allows photoactive light to pass.  The soap solution is collected at the bottom of the glazing and sent to the sump for recirculation.