Do you dream about living in a home that’s off-the-grid and energy efficient? You aren’t alone! Many environmentally and financially-minded consumers today are prioritizing energy and cost efficiency in their home buying or building. When it comes to saving money and achieving energy independence, off-grid, passive solar homes have been getting a lot of buzz.

Passive solar design has been around for centuries (check out this article on the history of passive solar) since people first learned to build their homes to take advantage of the sun’s position to trap heat in the winter and stay cool in the summer. The basic principles that were discovered thousands of years ago remain the same, but modern technology has improved upon these elements to ensure that today’s passive solar homes are more efficient than ever before.

The Basics of Passive Solar Design

Whether you’re building a new home from the ground up or renovating an existing structure with passive solar principles in mind, you’ll want to consider the following:

South-Facing Windows

In order to use the sun’s rays to heat your home (passive solar heating), you’ll need apertures (windows) that are appropriately placed to let the light in. In the northern hemisphere, this means that the majority of windows should be south-facing so they receive sunlight during the winter months when additional heat is needed. For best results, experts recommend that south-facing windows are positioned to receive direct sunlight from 9:00 am to 3:00 pm, drawing in warmth from the sun at its peak strength.

In a “direct gain” passive solar system, these windows will utilize 60-75% of the energy from the sun. Passive solar home-builders or renovators are advised to maximize southern exposure by elongating homes along the east-west axis.

Thermal Mass

While windows are positioned to let in the maximum amount of sunlight during winter months, that energy must be stored somewhere in order to sustain heat throughout the evening and night. The second half of the equation is thermal mass materials which have the capacity to absorb, store, and distribute heat energy from the sun. Material with thermal mass have innate qualities that support both heating and cooling - popular examples include masonry walls, concrete floors, ceramic tiles, and water containers.

When the sun strikes these components during the winter months, they will absorb heat and radiate it to continue heating the home after the sun has set. In the summer, when kept out of the sun, the high density of these materials keeps them cold and provides a cooling effect.

Shading or Controls

The final components of an effective passive solar heating and/or cooling design are the controls that can be used to increase or decrease sun exposure. These can include landscaping features such as shade trees or berms around the north, east, and west of the home, as well as awnings, overhangs, or shutters that can be adjusted to block the sun during the summer heat. Because of generally higher sun angles during the summer, experts can recommend overhangs or angled roofs that admit the sun’s rays during winter but block them in the summer. This Sun Calculator can help you get an idea of the angle of the sun in your location.

Adding “Active Solar”!

The principles of passive solar design for heating and cooling aren’t new, but technological advances now allow homeowners to not only limit their dependence on outside energy providers but to erase it entirely. A passive solar home with active solar components can direct the sun’s energy to heat or cool a home and also provide for its additional energy needs such as lighting, appliances, and more.

Active solar design includes the use of photovoltaic solar panels to collect and store energy, either by heating liquid or air, or modern electronic systems connected to battery storage (check out our article on Solar + Storage). Adding solar panels to a passive solar home doesn’t impact the home’s ability to heat and cool itself, but replaces grid-dependent energy systems to provide a truly off-grid, energy independent lifestyle. That’s why many passive solar designs today include solar panels or other alternative energy sources.

The Financial Value of Passive Solar Design

Passive solar homeowners eliminate many expenses and utility costs associated with home ownership and greatly increase the rewards of their investment in their home. By cutting the cord from utility companies and producing and storing their own energy, homeowners can achieve true energy independence and save money at the same time.

My wife and I are in the process of building a passive home on our small farm in Platte County, MO. The home, which is currently under construction, will include a very affordable off-grid Solar PV system in addition to many of the passive solar design principles discussed in this and previous articles. Contact us for access to a Facebook page where you can view our construction approach and progress as well as a financial assessment detailing how we’ve made our project more affordable than others.

At Solar Design Studio, we understand the many options that are available to home or other property owners and guide them through the planning and decision-making process to ensure that they get the most out of their solar energy investment. If you have questions for our solar experts, contact us today to start your journey toward solar-powered living.

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