PASSIVE SOLAR house design

Design for climate

Passive solar design creates buildings that have comfortable temperatures day and night, year round, without relying on artificial heating or cooling (defined as “active” temperature control systems). Mind you, passive solar requires active occupants – they need to adjust window & door openings, open & close curtains. Passive solar design also reduces electricity demand for lighting (by maximising daylighting) and refrigeration (with cool refrigeration bays and cool pantry design).

Passive solar houses need not cost much more or look terribly different to conventional ones. There are thousands of examples around the world built by countless people, from top architects to illiterate peasants. Here is one example that suits our climate (warm temperate/ cool subtropical NSW mid north coast). More examples can be found in “our work”.

ORIENTATION  

from 20 º East to 15 º West of true North.

PLANSHAPE

A long axis facing North, maximum width about 7.2m. The most used rooms e.g. living area should have cross ventilation, i.e. windows in two walls.

GLASS PLACEMENT

Most glass to the north, more to the south for cross ventilation, minimal glass to east and west avoids summer overheating.

ROOM PLACEMENT

The most heavily used daytime areas (kitchen, living) to the north, for best solar access.

CROSS VENTILATION

for summer cooling is probably more important in this area than winter heating. Air needs to be drawn into the room, pass over the body (to get the evaporative cooling effect of sweating) and escape. Cross ventilation is limited by the smallest windows, so south facing windows need to be reasonably large. Ideally, precool the incoming breeze by passing it under a breezeway, east facing roofed deck or pergola, or umbrella shaped shade trees.

EAVES

Carefully set to exclude summer sun and admit winter sun. The critical angle is about 55º.

INSULATION

is always lightweight – bubbles of trapped air in various forms. We use manufactured batts but traditional materials include thick, thatched roofs. Insulation retards heat flow, reducing summer heat inflow and winter heat losses out.

Glass (even double glazed performs far worse than a wall) has almost no insulation value. Windows need careful placement and good curtains with pelmets.

THERMAL MASS

Slowly absorbs and releases heat, evening out the daily extremes of temperature. Thermal mass is any heavy material, like brick, mud brick, stone, concrete. Thermal mass is confusing because it is good at storing energy but poorly insulated. A general rule is that heavy construction costs more than lightweight.

INSULATED THERMAL MASS

is the bees knees in passive solar for temperate climates because it gets the best of both worlds and has a good cost/ benefit ratio. Examples are: timber frame on concrete slab, reverse brick veneer (insulated timber framed walls on the outside, brick on the inside). A house we designed at Leeton has very well insulated, lightweight external walls and strategically placed heavy concrete block internal walls, rendered and filled with gravel.