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PASSIVE SOLAR


Heat naturally moves from warmer materials to cooler ones. Passive solar practices take this natural law into account, using the power of sunlight to reduce energy usage.

In passive solar, designers and builders leverage knowledge of solar geometry, window technology and local climate to make decisions about building design. With simple elements like south-facing windows, overhangs and natural ventilation, they can reduce or even eliminate the need for mechanical cooling and heating and daytime artificial lighting.

Passive solar can cut heating bills by 50%, yet it costs very little (if anything) to incorporate it into building design. Buildings designed for passive solar also boast the added comforts of natural light and airflow.

To learn more about passive solar, consult the FAQ below.

Passive Solar FAQ

  1. Is passive solar a good fit for me?
  2. What are the three passive solar design techniques?
  3. What are the requirements for passive solar window design?
  4. How much does a passive solar system cost?
  5. How much money and energy will I save?
  6. What should I keep in mind if I’m hiring a contractor?
  7. What rebates and incentives are available for passive solar?
  8. Are there any laws or regulations I need to be aware of?

1. Is passive solar a good fit for me?

Passive solar design is best incorporated before a building is built. If you are thinking about building a new home or building, you should consider adding passive solar elements. Passive solar can add energy savings and value to your project at little to no cost.

There are also some simple ways to apply passive solar principles to your existing home or building:

  • Open shades on south-facing windows during the day to allow more of the sun’s heat in
  • Install ENERGY STAR® qualified windows
  • Seal all gaps around windows and doors to minimize air leaks
  • Install roof overhangs to provide shade for your home in summer and increase solar heat gain in winter
  • Plant trees near south, east and west-facing windows to provide shade in the summer and solar heat in the winter

Passive solar works best in homes that are well sealed and insulated. Check out the energy efficiency information on this website to learn more.

For more information:

Visit Energy Savers' passive solar home design page.

Download the U.S. Department of Energy’s passive solar design technology fact sheet.

2. What are the three passive solar design techniques?

There are three main passive solar design techniques:

Direct Gain
Designers employ large, south-facing windows to take advantage of the best direct sunlight and incorporate materials that absorb and store the sun's heat into the sunlit floors and walls. With this approach, floors and walls heat up during the day and slowly release heat at night, when the heat is needed most.

Indirect Gain
This technique relies on very thick, dark-colored, south-facing walls, called trombe walls, to absorb heat during daylight hours. A pane of glass or plastic glazing, installed a few inches in front of the wall, helps hold in the heat. The wall heats up slowly during the day. Later, as it cools, it releases its heat through the night.

Isolated Gain
In isolated gain applications, a space is created to collect heat. Ventilation then moves collected heat into the rest of the house. Greenhouse-like sunspaces are the most common form of isolated gain.

3. What are the requirements for passive solar window design?

Proper window type and placement are essential to passive solar design.

In heating-dominated climates such as Colorado, windows should generally face south so that they can collect solar heat during winter months when the sun is low in the sky. In the summer, overhangs, awnings and blinds should shade the same windows to preserve cooler indoor temperatures.

Window requirements:

  • A solar heat gain coefficient (SHGC) of greater than 0.6 to maximize solar heat gain during the winter
  • A U-factor of 0.35 or less to reduce conductive heat transfer
  • A high visible transmittance (VT) for good visible light transfer
  • Low-emissivity window glazing can help control solar heat gain and loss in heating climates.

On the east, west and north sides of the building, windows should be minimized as much as possible without sacrificing natural light. These windows should have a low SHGC and/or be shaded.

4. How much does passive solar cost?

Passive solar is not inherently expensive; it is simply a design strategy that can become an integral part of any building plan. If you work with a designer and builder familiar with passive solar technology and techniques, a passive solar home may cost no more than a conventional one.

In existing homes, passive solar techniques can easily be incorporated into how you manage your home’s energy use and can be low to no cost.

  • Open shades on south-facing windows during the day to allow more of the sun’s heat in
  • Install ENERGY STAR® qualified windows
  • Seal all gaps around windows and doors to minimize air leaks
  • Install roof overhangs to provide shade for your home in summer and increase solar heat gain in winter
  • Plant trees near south, east and west facing windows to provide shade in the summer and solar heat in the winter

5. How much money and energy will I save?

Well-insulated and air-sealed homes will get the most benefit from passive solar. The amount of money and energy you can save with passive solar depends on which techniques you implement, the size of your home and your local climate; it is not uncommon to achieve savings of as much as 50%.

6. What should I keep in mind if I’m hiring a contractor?

For general tips, including what to ask a potential contractor, how to compare bids and how to monitor quality, please visit the How to Hire a Contractor page.

In addition to the general tips in our How to Hire a Contractor page, you may need to consider some specific issues when hiring a contractor for this particular kind of work. Here are some additional things to keep in mind:

When choosing your building designer and builder, try to find contractors who have experience with passive solar building design.

For New Construction

Here are some important questions to ask your homebuilder when designing your new home:

  • Where should we place the windows? How big? How many?
  • Should I consider roof overhangs?
  • How can I maximize sun exposure to my windows?
  • Can I install special flooring that absorbs the heat from the sun?
  • What types of shades/blinds work best to maximize the sun’s heat?
  • Can I install energy-efficient windows?

For more information:

To search a list of contractors in your area provided by the Better Business Bureau, visit the Energy Action Planner, right on this site.

7. What rebates and incentives are available for passive solar?

See the Energy Action Planner for additional information on financial incentives in your area.

8. Are there any laws or regulations I need to be aware of?

Be sure to check local regulations regarding building codes and passive solar design requirements when considering a new building project.