Thermal I - Passive Solar & Comfort

Course competency

On completing this course you can calculate the sun's position at your site for any date, establish true south in the field, size a south-facing overhang so it shades fully in summer and admits fully in winter, choose between direct, indirect and isolated gain systems, size glazing against available thermal mass, specify glazing and shading, and explain to a client why the building will be comfortable without a furnace.

Why this course exists

Course 3 and Course 4 built walls. This course decides where the building faces and what the sun does to it - and that decision outranks every material choice that follows.

A superbly built tire wall in a badly oriented building performs worse than an ordinary wall in a well-oriented one. Orientation, glazing area and overhang depth cost nothing at design stage and cannot be changed afterwards. They are the highest-leverage, most irreversible decisions on the project.

Doug Balcomb's line, which every passive solar designer eventually repeats: "Orientation is 80 percent of passive solar design."

What "passive" means, precisely

A passive solar building uses the building itself - its orientation, massing, glazing and materials - as an integrated solar energy system.

No pumps. No controls. No moving parts. No external energy input. Everything responds to an input of energy through the physics of the building.

This is not a poorer version of a mechanical system. It is a different category of thing, and it has a property no mechanical system has: it cannot break down, because there is nothing in it to break.

That is the resilience argument, and it is the one that lands hardest with clients. In an extended winter power failure, the interior of a passive solar building will be dramatically warmer than a conventional building - not because a backup ran, but because the building is doing what it always does. For off-grid work, for disaster relief, and for affordable housing where a utility shutoff is a real risk, that property is the whole point.

The numbers that justify the discipline

Buildings account for roughly 30% of global final energy consumption and more than 55% of global electricity consumption. Operationally they produce about 28% of energy-related CO₂ emissions; including the emissions embodied in construction, the figure is just under 40%.

A correction worth carrying forward. Some older Pangea material states that "buildings use about 48% of all electrical energy generated by humanity, of which 40% is for operating and 10% for construction." That is a garbled version of a US-specific figure and it is not correct as stated. Use the IEA figures above. They are more conservative, more defensible, and still make the case overwhelmingly - buildings are the largest single lever available.

And buildings do not have to use fossil fuels at all. Zero-energy buildings can be built today, and the small residual energy demand can be met from photovoltaic, wind or other renewable sources (Course 10).

Course structure