We've been cooking up a new little project for our urban plot at Hereabouts - a wee space for soaking up the sun and growing more food.
Out of some recent adversity an opportunity was born. Last fall, our neighbour cut down all the mature mayday trees that separated our yard from hers (they had developed a fatal fungus). I was stunned by our sudden exposure and bitterly mourned the loss of that leaf-dappled space, the honeyed perfume of the blossoms in spring, and the birds that frequented those branches. Meanwhile, my husband perceived that an opportunity had opened up. What was previously the shadiest section of our yard now had unimpeded southern exposure. Plus, the greenhouse we built almost twenty years ago with salvaged windows and lumber was near collapse. A fresh greenhouse in the newly sunny spot, perhaps?
So we've been working out a design - something small enough that we can avoid a building permit and short enough that it won't shade our well established food-bearing perennials behind it. In our climate, there's really only one greenhouse design that will be both effective and efficient and that's a passive solar one. Conventional greenhouses made entirely of translucent glass or plastic suffer from overheating on warm, sunny days and rapid heat loss the rest of the time. Passive solar design, similar to what we used for the tiny house, mitigates the need for energy-intensive heating and cooling through a careful combination of elements like insulation, thermal mass, and a south face finessed to take advantage of seasonal sun angles.
It can feel pretty technical when you first delve into the world of passive solar. But in truth, it's an elegant design system that just requires a basic understanding and a willingness to sketch out some possibilities on graph paper (or with modelling software, but that's way beyond me!). Two resources I've relied on extensively are The Year-Round Solar Greenhouse book and Verge Permaculture's passive solar greenhouse DIY e-book (no longer available, but they offer courses and have loads of free tips online).
Cochrane has a woefully short growing season with random late and early frosts, occasional hail, and an increasingly bold population of browsing deer - great arguments for a greenhouse! Because of its design, this new structure will be far better at extending our growing season than our current one. It should boost our yard's capacity to feed us (and our B&B guests), restore some privacy between us and our neighbour (who we actually really like!), and provide a delightfully sunny, plant-filled shoulder season haven.
I wouldn't have thought it at the time, but perhaps that drastic loss of trees allowed us to develop a more resilient urban allotment. The maydays are still sorely missed, but I do look forward to the November greens they made space for!