After much research and observation, I have started my dream of building a passive
solar greenhouse. I’ve decided to use Permies as the medium to share my
project. I love this site.
I drew inspiration from many sources but the core design came from uMinn’s
Deep Winter Greenhouse project. The exact
plans are self-designed and so far construction has been just me, but definitely influenced by what I’ve learned from other threads on Permies. I welcome questions and comments.
Some quick points:
• I’m in New Brunswick, Canada. Zone 4.
• Growing goal is to extend my season from March and to November (outdoors the growing season is only June to September)
• Dimensions: 32’W x 16’Dx 14.5’H (I tried to hit 2-1-1 ratios). Oriented so the long side faces South.
• 2x6
wood construction, steel roof/siding, insulation TBD (narrowed down to mineral wool or fiberglass)
• It will have a Climate Battery/GAHT (Ground to Air Heat Transfer).
• Glazed with SolaWrap
Climate Battery:
The GAHT was a huge factor in the overall design and cost, but I felt it very much inline with my goals. I could have built several hoophouses for the cost of just this system but I want to grow in March, not 4x the size in May when I’m already busy outside. I also don’t want to rely on supplemental heating. I’m going with the full rock bed style like uMinn instead of layers of drainage pipe surrounded by
native soil. I live very close to a quarry that has suitable rock and eliminating hundreds of feet of pipe seems very appealing from a construction standpoint.
Foundation:
The foundation is on
concrete piers, as inspired by some of the Ceres
Greenhouse photos I saw
online. I did not want any wood touching soil, but also didn’t want a full concrete “basement”. This option seemed the perfect hybrid. The pit was excavated down 4’, I went with 6ft tall 8” piers on 19” footings. I’ll be landscaping the perimeter so the new grade is a foot higher the originally, sloping away. Doing the math that leaves a foot of clearance above the ground before any wood construction. The entire perimeter of the foundation is going to be wrapped in R10 styrofoam insulation. The foot that is above ground will be covered with flashing.
Glazing:
For the glazing wall, originally I was going to go with a straight wall at 60 degrees, glazed with inflated poly. Much like the Bradford Research Center
greenhouse. I ultimately opted for a gambrel style roof instead. Partly because a straight wall calculated to 13’ and I figured if I’m going to splice, why not use as much of both 8’ pieces as I can and can some head space by putting them at an angle. Partly because I feared the plastic would “bounce” a lot on a flat surface whereas having a change in angle would keep things tighter. Partly because I really like the look of Penn and Cord’s greenhouses (though structurally very different). Although I haven’t purchased the glazing yet, my current plan is go with with SolaWrap. My quotes have it at double the price of poly over a 12 year timeframe, but that doesn’t account for the labour savings of replacing poly every 4 years or the blower to inflate it. Polycarbonate is a dream; it’s way outside my initial budget. R-values seem comparable on all 3.
This build
greenhouse is more of a starting point for personal growth than just a one time project to grow more food. I have many future projects in mind for the interior, often things that I can’t do in the house because it would void my home insurance. For starters, a
rocket mass heater. Secondly, interior rolldown bubblewrap as an insulated curtain. Even with an insulated glazing surface, that wall is a relative gaping hole when compared to the rest of the structure.
I’m late in getting this
thread started, as the build has already begun! So here are a couple pictures to get things going. One of the profile of the
greenhouse (not to perfectly to scale), and another showing the inaugural ground breaking.
Plenty more to come of course. Since it’s not entirely built yet, still chances to change as opportunities are discovered.