Winter: maximize solar gain while minimizing loss of heat through window area.
Summer: minimize solar gain while minimizing loss of cool air.
All Seasons: Optimize thermal mass to dampen diurnal temperature swings.
Window area and placement guidelines for this site:
Optimal south-facing window area = 12-15% of total house floor area or ~30% of the south facing wall surface of the house
Maximum north, east, and west-facing window area = <5% of total floor area, but enough for daylighting
Maximize solar gain in winter and minimize it in summer:
click for more info.
We modelled the influence of different roof overhangs and roof angels to see the effect on shading and passive solar gain depending
on the season and the stand of the sun. See our models here.
Thermal mass vs. insulation:
With simple information about the size of the house, the window areas on each orientation, and the local climate, we conducted energy
simulations to examine whether our money was better spent on more insulation or more thermal mass.
These simulations clearly showed that building thicker walls thicker to add more insulation
only made a 1% difference in the thermal performance of the house. By contrast, adding a concrete
floor with radiant heating for thermal mass would significantly improve the thermal performance.
Thus, given our limited budget, we chose standard, easy to construct (i.e., inexpensive) 6” thick
walls (R21) and invested in 2.5” thick concrete floors with radiant heating. The other advantage of
radiant heating is that we could heat the fluid with solar water heating panels (link to below).
Title 24 Standards for insulation for climate zone 16:
Roof – R38
Wall – R21
Floor – R19 (with crawl space, R30 w/out)