Passive Solar Design: Heating and Cooling Using Natural Sunlight

Heat and light from the sun is free, renewable and easily accessible. Why not use it to light, heat, and cool your building? Passive solar design uses simple design elements such as building orientation, windows, shading, insulation, and thermal mass to strategically harness the sun’s energy to heat and cool a building. Passive solar design is practiced throughout the world and has been shown to produce buildings with low energy costs, reduced maintenance, and superior comfort.

Depending on your location and your building’s unique design elements, passive solar design can cut a building’s energy use by 30 to 40 percent at no extra cost. In other words, if your monthly utility bill is $300, you could save up to $100 per month, or more than $1,200 per year, simply by incorporating design elements that work with the sun to harness its energy.

In addition to monetary savings, passive solar design has several other added benefits. The New Mexico Solar Energy Association organized the advantages into the following acronym:

• High energy performance: lower energy bills all year round.
• Investment: independent from future rises in fuel costs, continues to save money long after initial cost recovery.
• Value: high owner satisfaction, high resale value.
• Attractive living environment: large windows and views, sunny interiors, open floor plans.
• Low Maintenance: durable, reduced operation and repair.
• Unwavering comfort: quiet (no operating noise), warmer in winter, cooler in summer (even during a power failure).
• Environmentally friendly: clean, renewable energy doesn't contribute to global warming, acid rain or air pollution.

Core Design Elements

Passive solar design takes a whole-building approach and involves careful planning in the design phase, before construction begins. Passive systems are simple, have few moving parts, and require minimal maintenance or mechanical controls.  During the design phase, architects pair knowledge about how sun will reach the building with design elements that optimize the collection of the sun’s thermal energy. Operable windows are strategically placed to take advantage of local breezes, roof overhangs are incorporated to provide proper shading, and landscaping is planned to provide shading and windbreaks.

Passive solar building design centers upon the following five core principles, as defined by the Solar for Energy:

Orientation: Window and building surfaces are positioned to maximize solar heat gain in the winter and optimize shading in the summer.

Windows: Operable windows collect heat and light and can also be opened to provide ventilation when cooling is needed.

Building Shade: External overhangs provide shade for cooling during summer months. Overhangs are strategically sized to block the high summer sun while still allowing the winter sun, which shines from a lower angle, to enter. Other shading techniques include awnings, shutters, light shelves, vine trellises, and landscaping with trees that shade the building.

Insulation: Good insulation forms a barrier between the outside climate and the building’s interior to maintain the indoor temperature. Insulation reduces the energy needed to keep the building cool in hot weather and warm in cool weather.

Thermal mass: Materials such as concrete, stone, and brick absorb and store heat until it is needed. Thermal mass is important for providing back-up heat when sun is not available.

Passive Solar Design in Alexandria

Passive solar design is a simple, elegant, and cost-effective technique for harnessing free, renewable solar energy to heat and cool a building. T.C. Williams High School incorporates passive solar design elements such as windows, light shelves, and orientation.

(Source: Department of Energy) 

Additional Resources

Passive Solar Home Design | Department of Energy
Top 4 FAQs Every Solar Home Builder Should Know | Solar for Energy
Passive Solar Image Gallery |Green Passive Solar Magazine