I live on edge of zone 4/5 in WI. Thinking about building a greenhouse with only south side glazed. Similar to what Gary is doing except I was think vertical wall where he has pitch on ithttp://www.builditsolar.com/Projects/Sunspace/LowMassSunspace/Greenhouse1.htm . I have thinking of this for many years just never got around to do it. think this will let enough light in for summer growing? I plan on other walls/ceiling to be well insulated to keep winter heat in and summer heat out and maybe installing solarhot water heat for winter.
It is simple to determine how much light you can get at different times of year. just draw a scale drawing cross section of your planned building. Then set protractor on the drawing. You will need to know the angle of sun on your latitude on equinoxes and solitices. Use the protractor to determine how far light will penetrate the building at different times of the year. Then adjust the height of the glazing to allow enough sun. Play with different widths and heights to get the layout you want sunlit. Of course you must consider snow load and other structural factors.
the sunspace test featured recently on builditsolar is derived from a greenhouse design which I beleive was first developed by Laval University in the early seventies.
Find a copy of "The Passive SolarEnergy Book" by Edward Mazria at a used book store, lots of info on the design plus it has a set of clear plastic solar calculators in the back...
You can see one of these built with cold frame additions at Wellspring in Newburg WI. (near West Bend) here's their homepage:
I wish more of us in the "northern climes" would be aware of/embrace this design, makes tons of sense to me: - especially with the optional addition of cold frames to the south as additional growing space/heat collectors.
Hoops may be relatively cheap, but...I like the above design because it can be well insulated and can easily incorporate recycled materials...
again, it's all about the concept; understanding the fundamentals, and local conditions/climate/site/needs....
Andor aka mechartnik
we CAN build a better world
Location: Central Ohio, Zone 6A - High water table, heavy clay.
posted 6 years ago
The one I built is quite large (primarily because I got a steal on the poly panels), but they can be sized to your needs.
Where we are is very flat with lots of wind and a hoop house is a non-starter unless you like replacing plastic sheeting.
The county building inspectors were actually pretty cool with it once they saw how we built it, but I got a few puzzled looks during the plan approval process. I just kept telling them it was basically an overbuilt pole barn with a clear roof...
The question of roof pitch ultimately depends on what you want to grow. If you want to grow during the winter a steep roof pitch helps, if you want to ripen fruits and veggies in the summer you will want a more shallow roof pitch. If you want the best sun in the summer (when the sun is at it's best) then a 3:12 roof pitch should be about right for your latitude.
On the subject of the New Alchemy Institute, the Arch is a great place to go for ideas as well. They've built a number of bioshelters in the 70's and 80's.
It will take a second but here is their link for the Bio-Shelters Primer. They have lots of good publications available on their website.