Passive solar home design

With a southern orientation and well placed windows, passive solar homes can reduce heating requirements by an easy 25% without adding any cost.

Passive solar home design
Passive solar home design © Creative Commons

Passive solar is so aptly named because there are no wires, panels or batteries and nothing to break down. It's just about design, and it isn't a new concept. Humans around the globe have been incorporating passive solar design features into their homes for thousands of years.

Active solar refers to any system of solar panels whether it be photovoltaic power generation, or thermal solar where liquid passing through tubes collects heat to be redistributed through your house.

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According to NASA, every day the sun provides the earth with 10,000 times the total energy consumed by humans. A passive solar house is simply one that has been designed to take advantage of that.
Passive solar home
Passive solar home. © Ecohome

Passive solar is yet another green building feature that will save you money while improving your quality of life. Lighting in the artificial environments we create for ourselves affects natural human biorhythms and can lead to fatigue and reduce our ability to concentrate.

Whether we realize it or not, we are all directly affected by the amount and quality of light we are exposed to. To support that fact, 99.5 % of LEED certified commercial buildings that offer outside views and natural light report higher productivity and worker satisfaction.

If you still need convincing, simply watch the dynamics in any coffee shop on a sunny winter day as people circle like sharks to get a window seat.

How it works

There are two dates that form the cornerstone of passive solar design, December 21st and June 21st when the sun is at its highest and lowest points.

Window size and placement along with overhangs and shading are determined based on these two dates to ensure maximum exposure at midday December 21st, and maximum shading at midday June 21st.

Passive solar window design
Passive solar window design. © Ecohome

These two dates are important because while you want to absorb as much heat as possible in winter, insufficient shading in summer can mean any energy you saved in the winter will probably go into air conditioning.

In the design phase you can determine what parts of your floors and walls will be exposed to the sun, and place materials there that will absorb thermal radiation. Darker materials with heavy mass like concrete, stone or brick will absorb the most heat. For walls you can simply add a second layer of drywall (or more), if you want to keep a traditional look.

Window choice is important, and double or triple pane gas-filled windows with low-e coatings will ensure that the heat gained in the daytime outweighs the heat lost at night.

Thermal mass for heat collection
Thermal mass for heat collection.
© Ecohome

Heat absorbed in the day is released throughout the night, and a highly insulated passive solar home can actually absorb enough heat in the day to eliminate the need for any secondary heat source, even here in Canada. Granted this is extreme green building, but energy modelling proves that it can be done.

Using software developed for the German PassivHaus standard, a study by Ecohome engineer Denis Boyer has determined the wall, roof and window R-value requirements needed for a passive solar home in the Canadian climate that requires no heat source.

To attain a completely self-heating home requires substantial insulation of course, but added costs would be balanced first of all by not needing to install a conventional heat source, secondly by enjoying a lifetime of free heat.

Maison Orfie
Maison Orfie. © Ecohabitation

It's important to keep in mind that passive solar heating is not something that should intimidate you in the design phase, and it isn't an 'all or nothing' concept. It is an ancient and relatively easy concept that has been overlooked in home construction for generations.

It is imperative for the planet and the success of societies that solar heat collection not only be reintroduced into home design, but that it be the very first thing we consider.