Passive Solar Design Basics

Plan a comfortable, energy-efficient home that saves you money on heating and cooling with these passive solar design basics.


  • Solar Living Room
    The great room of the Myers home is designed to let in plenty of sun in the winter, while blocking it in the summer.
    PHOTO: DAVID WRIGHT
  • Passive Solar Basics
    The angle of the sun changes throughout the year, so a well-designed home can let in the sun in the winter while blocking it in the summer.
    NATE SKOW
  • Myers Family
    The Myers family lives in a house optimized for passive solar.
    DAVID WRIGHT
  • Floor Plan
    The floor plan of the Western Solar Farmhouse features a great room with good solar exposure and is designed to include ample porch space.
    DAVID WRIGHT
  • Western Solar Farmhouse
    The Western Solar Farmhouse is an example of classic passive solar home design.
    DAVID WRIGHT

  • Solar Living Room
  • Passive Solar Basics
  • Myers Family
  • Floor Plan
  • Western Solar Farmhouse

Passive solar design begins with the simple idea that you can build a house that uses natural heating, cooling, ventilation and daylighting. These homes require much less fossil fuel energy to heat and cool than conventional homes do, which is better for the environment and saves passive solar homeowners money. Passive solar homes are comfortable to live in because they are designed to radiate heat in winter, maintain a comfortable year-round temperature, ventilate naturally, and let in plenty of natural light.

I became interested in sustainable design, specifically passive solar design, as a young architect — first while working in the Peace Corps in Africa, and later while working professionally in New Mexico. The details of any particular passive solar home design depend on the climate and the specifics of the site. Over the course of my 35-year career, I’ve designed a variety of passive solar houses throughout the country using different configurations of south-facing windows, sunrooms and other passive solar design features. (For specifics on one of them, read “The Western Solar Farmhouse: A Passive Solar Design” near the end of the article) What follows are the principles used to design any passive solar home.

Passive Solar Design: House Orientation and Window Placement

The first consideration for optimizing passive solar energy is to select a house site with adequate solar exposure. For solar heating in winter, a good measure of solar exposure is to have at least four hours of direct solar gain on the winter solstice. The best orientation is to have the “solar” side of the house face within 15 degrees of true south. In climates where summer heat is a major concern, it’s a good idea to aim the solar windows a little east of south to get morning sun in winter and avoid the intense western sun in the warm season.

Typically, you would locate the day-use rooms, such as a living room or family room, on the south portion of the home’s floor plan to allow the greatest amount of solar energy to penetrate these rooms on winter days. This layout also allows you to take advantage of the sunlight and view of the outdoors.



The “shell” of the house is composed of exterior insulated walls and “glazing,” or windows. In a conventional home, the window area is equally distributed on all four sides of the home, or the majority of the window area may be focused on the direction with the best view. For a passive solar design, one would locate more of the window area on the south side, which has the best solar access. Some windows would be placed on the east and west sides of the house for daylighting and cross-ventilation with only a few windows to the north.

The glazing is important. Choose high-quality, tightly constructed windows to reduce air infiltration. At a minimum, use double-insulated glass. Some of my favorite high-quality windows are Loewen metal-clad wood windows, but all-vinyl windows are more economical and perform well. Double glazing is adequate for most climates, although in locations with severe winter conditions, triple glazing is advisable to reduce heat loss and condensation on the glass.

GreenGenie
5/3/2021 11:17:15 AM

The materials commonly used to provide thermal capacity do not perform well. They take up and release heat too slowly, do not store much heat and only function if they are interior surface (therefore not covered by carpet etc). Materials such as brick, concrete or stone are not thought of as 'ecological, sustainable or low embodied energy materials', and if they are cold - they draw away or 'rob' the radiant heat from your body. In a climate-warming-heatwave, such materials will saturate with energy and not be able to be cooled overnight and the dwelling will become too uncomfortable to live in. You will feel cooler in a lightweight un-insulated building that provides shade but cannot absorb and re-radiate heat. Water is free (as precipitation) and is a much better heat storage material. Natural convection currents allow water to evenly absorb energy, and hot water is quite easy to move to where it is needed. I think the future of passive solar design is a carefully ventilated but air-tight, highly insulated, low thermal capacity building made mainly of renewable materials - a timber structure and wood-fibre insulation (this is the most efficient way to make the most of human and incidental heat gains), plus a small amount of Phase-Change-Material - which can be fitted above ceilings. PCM materials are lightweight and able to absorb and store many times more heat energy than concrete, and quickly release it when required. PCM could be manufactured from natural plant oils, rather than fossil fuels...


GreenGenie
5/3/2021 10:37:54 AM

The materials commonly used to provide thermal capacity do not perform well. They take up and release heat too slowly, do not store much heat and only function if they are interior surface (therefore not covered by carpet etc). Materials such as brick, concrete or stone are not thought of as 'ecological, sustainable or low embodied energy materials', and if they are cold - they draw away or 'rob' the radiant heat from your body. In a climate-warming-heatwave, such materials will saturate with energy and not be able to be cooled overnight and the dwelling will become too uncomfortable to live in. You will feel cooler in a lightweight un-insulated building that provides shade but cannot absorb and re-radiate heat. Water is free (as precipitation) and is a much better heat storage material. Natural convection currents allow water to evenly absorb energy, and hot water is quite easy to move to where it is needed. I think the future of passive solar design is a carefully ventilated but air-tight, highly insulated, low thermal capacity building made mainly of renewable materials - a timber structure and wood-fibre insulation (this is the most efficient way to make the most of human and incidental heat gains), plus a small amount of Phase-Change-Material - which can be fitted above ceilings. PCM materials are lightweight and able to absorb and store many times more heat energy than concrete, and quickly release it when required. PCM could be manufactured from natural plant oils, rather than fossil fuels...


Alexes
1/12/2016 2:08:46 PM

How much would it cost to build this home?




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