Heat Sink

Passive Solar Heating and Cooling - Ideas on How to Make Your Home More Comfortable

There is much talk about using solar energy to generate power, but at times we forget that we can harness the suns energy to heat and cool our homes by clever design.
There are relatively simple changes to basic home design that make our homes more comfortable, simply by understanding the orientation of your house and using well understood methods of blocking or allowing the energy of the sun into your home.

About Windows
The orientation of the windows is critical for solar heating. In the southern hemisphere, windows facing due north, while in the northern hemisphere, south facing windows allow passive solar heat to warm the house during the day. To maximise the heat gain, the house should have a "heat sink"  or trap that warms up and releases the stored warmth slowly. This is usually as simple as using the concrete slab a house is built on.  It can be more innovative, such as a wall of water filled containers or "bottles" built into a wall.  The most efficient windows for passive solar heating are high efficiency windows, usually multi-paned, gas-filled windows.  When used with wall, ceiling and floor insulation, they are highly efficient. Retrofitting an existing home with high efficiency windows and expanding the surface area of those windows on the sun facing side of the house will both increase the overall energy efficiency of the home and take advantage of passive solar heating.

Passive Heating
Passive solar heating usually relies on sunlight passing through windows or storing the heat in a "heat sink" that traps and releases its warmth over a long period of time.  Passive solar cooling however, relies on preventing sunlight entering and heating a structure, or by creating convection currents drawing air into the building as a cooling breeze.  None of these are new technologies, ancient cultures used these ideas hundreds of years ago.

Passive Cooling
Passive solar cooling is a technique of shading windows during the summer to prevent solar heat from entering the home. This can be as simple as having roof eaves of the proper depth to shade out the sun in summer but allow the lower angled winter sun to fall through the windows.  Alternatively a "solar pergola" with angled slats that allow sun to shine between the angled rafters at lower angles such as early morning or later in the day.  However, in the middle of the day, the slats block the sun and provide shade during the hottest time of day.  Deciduous trees can also shade windows in the summer but allow sunlight to enter windows in the winter. Trees also provide cooling by shielding from hot winds and cool the air from their transpiration. In winter, the trees break up any cold airflow over and around the house.

A well designed solar passive home is not only more comfortable, but also allows greater access to outdoor views. There are many ways to provide passive cooling and heating, even when retro fitting to an older existing home.

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