The Sunspace
This pattern is shaped by
Problem
When solar heat enters a dwelling through south-facing glass, it brings light and warmth — but distributed evenly through the house, it creates problems: south rooms overheat while north rooms stay cold, summer afternoons become unbearable, and the heat arrives when the sun shines, not when the house needs it. Yet blocking the sun to prevent overheating means losing the free heat that makes northern winters bearable. The tension: you want the solar gain, but you need to control where it goes and when.
Evidence and Discussion
The solution, known for centuries and refined through decades of passive solar research, is the sunspace — a south-facing glass room that captures solar heat but remains separable from the main dwelling. Edward Mazria's *The Passive Solar Energy Book* (1979) documented the principle: a sunspace acts as a thermal buffer zone, collecting heat that can be admitted to the house when wanted and vented outdoors when not. The key is the closeable connection. When a sunspace is permanently open to the house, it becomes just another room with too much glass. When it can be isolated — by doors, operable windows, or thermal curtains — it becomes a solar collector you can switch on and off.
The physics favor northern latitudes. At Edmonton's 53°N, the winter sun stays low — 13° altitude at solar noon on December 21 — and strikes vertical south glazing almost perpendicularly. A square meter of vertical south glass in Edmonton receives roughly 3.5 kWh of solar radiation on a clear January day, compared to 2.1 kWh on a horizontal surface. In summer, when the sun reaches 60° altitude, that same vertical glass receives far less direct radiation, and a modest overhang provides complete shade. The geometry that causes problems with ordinary south-facing rooms — too much summer heat, too little winter heat in the living spaces — is solved when the sunspace mediates between sun and house.
The Saskatchewan Conservation House, built in Regina in 1977, demonstrated the principle at 50°N. Its attached sunspace provided 25% of the home's annual heating through a combination of direct gain when doors were open and warm air circulation through a simple fan system. Monitored data showed the sunspace reached 30°C on clear winter afternoons when outdoor temperatures were -20°C, allowing occupants to open the connecting doors and flood the house with warmth. When the sun set, they closed the doors, and the house retained its heat while the sunspace dropped to near-outdoor temperatures. The Rob Roy Kelly Residence in Edmonton (1982), designed by architect Peter Frey, used a two-story attached sunspace as the primary heating strategy, reducing natural gas consumption by 60% compared to conventional homes of the same size. More recent monitoring by Natural Resources Canada's R-2000 program has confirmed that properly designed sunspaces in the prairie provinces consistently deliver 15-30% of annual space heating, with the range depending on glazing quality, thermal mass, and the discipline of the occupants in operating the connecting elements.
Alexander's Pattern 161, *Sunny Place*, calls for every building to have an outdoor space that is "ichiban" — the sunniest and most sheltered spot. The sunspace extends this idea inward: it is the ichiban place you can occupy in January, in a T-shirt, watching the snow fall. But it works only if you can close it off. In summer, the sunspace vents to the outdoors and the connecting doors stay shut; the house stays cool. In winter, afternoon sun heats the sunspace to comfortable temperatures; you open the doors and let the warmth in. At night, you close the doors. The discipline is simple, the reward is large.
Therefore
on the south side of any dwelling north of 45° latitude, create a sunspace — a glass-enclosed room at least 2.5 meters deep, with vertical south-facing glazing (SHGC ≥ 0.5), a dark thermal mass floor of at least 100 mm concrete or equivalent, and operable doors or windows connecting it to the main living space. Size the glazing at one square meter per eight to ten square meters of floor area served. Provide operable vents at the top and bottom of the sunspace for summer exhaust. The test: on a clear January afternoon with outdoor temperatures below -15°C, the sunspace should reach 25°C with no auxiliary heat, and when the connecting doors are opened, the adjacent living space should warm noticeably within fifteen minutes.