If you’re in the process of designing your next home, or you’re looking to redesign your current dwelling, now is the perfect time to consider harnessing the power of the sun. By now, most homeowners are aware of at least a few reasons as to why it’s a good idea. Solar reduces both your energy usage and environmental impact.
It’s also a solid home investment. According to a study by the Lawrence Berkeley National Laboratory, buyers are willing to pay an average of $15,000 more for a home that’s equipped with solar power. What’s more is that in a growing number of states, you can leverage Solar Renewable Energy Certificates to sell your unused power back at a premium.
But your investment in solar doesn’t have to end with the installation of a few basic panels on your roof. You can further benefit from this renewable energy source by incorporating passive solar design in your home. This takes advantage of your property’s location, materials and the local climate to significantly reduce energy usage.
How Passive Solar Design Works
A passive solar home uses energy-efficient strategies to reduce heating and cooling loads. The reduced loads are then met in part or even entirely by solar energy. This starts with the collection of heat through south-facing windows. The energy is then retained in materials that can store heat, also known as thermal mass.
The area of glazing and thermal mass quantity will determine how much of your home’s heating load can be met by the passive solar design. This is known as the passive solar fraction. The ideal ratio of glazing to thermal mass will vary depending on the local climate. Passive solar design provides year-round sunlight and comfort during cooler seasons.
Of course, in order for your home to harness the power of the sun, it needs to be able to “see” it. If you’re planning to build on a new property, consider how its surrounding landscape will look in the coming years.
Future multi-story developments and the growth of trees might cause problems in the future. Fortunately, most areas have zoning and other land use regulations that are designed to protect your access to solar power.
Elements of an Effective Passive Solar Design
Window Orientation: You’ll typically want your windows and other solar energy-collecting devices to face within 30 degrees of true south. They should avoid being shaded by other buildings or trees between morning to early evening during heating season. Come cooling season, they should be moderately shaded to avoid overheating.
Distribution: The transfer of heat from where it’s collected to where it’s stored or used is done by conduction, convection and radiation.
Conduction is the transfer of heat between two objects that are in direct contact with each other, such as when the sun warms your bed in the morning. Darker objects are better for heat conduction.
Convection is the transfer of heat between fluids, including air. For instance, some homes use small fans to move heat to where it’s needed. Radiation is when you feel the heat an object emits.
Thermal Mass: In a passive solar home, thermal mass absorbs heat from the sun during heating season, while in cooling season, it absorbs heat from warm air inside the house. Common vehicles for heat absorption include brick, stone, concrete and tiles. The better insulated a home is, the more thermal mass it can retain.
Control Strategies: In order to make the most of the heat your home absorbs, you’ll need to implement a number of control strategies. For instance, a roof overhang can shade vertical south-facing windows during cooling season. You can also use sensors to signal a fan to turn on and move heat where it’s needed or use vents to allow or restrict air flow.
In reality, not all homes can be entirely heated with passive solar design. Even if yours manages to be successful in this regard, the use of non-passive solar will provide a host of additional benefits. Standard solar panels can be used to provide energy to just about wherever it’s needed in your home, instead of just heating systems.
An important consideration here is whether or not you should incorporate a battery storage system to retain the power your solar panels absorb. Unsurprisingly, the answer is a clear yes. In doing so, you can store surplus power and sell it back to the grid, further offsetting the cost of your investment. It will also prove convenient during blackouts.
To assist you with your battery storage installation, you’ll want to enlist the help of a professional and reputable battery storage company. They’ll help you get the most affordable and efficiently designed system, as well as one that doesn’t leave a large footprint in your home. That said, here’s how you can make your passive design more effective.
Creating an Effective Design
While fairly simple on paper, an effective passive solar home design requires the consideration of a number of variables. Ideally, you’ll enlist the help of an experienced designer, who can use computer models to simulate the details of your design in different configurations until the most effective, affordable and aesthetically pleasing solution is compiled.
The designer will consider elements such as insulation and air sealing, thermal mass location, type of thermal mass, window location, shading and type, as well as auxiliary heating and cooling systems. These elements will be applied using three design techniques, namely direct gain, indirect gain and isolated gain.
With the direct gain technique, the floors and/or walls of your home will absorb heat through south-facing windows as the sun rises. The heat (thermal mass) is then stored and released during the evening as the home cools. In addition to storing heat in building materials, some homeowners use water containers.
This is because water is capable of storing twice as much heat per cubic foot of volume as masonry materials. However, water thermal storage does require careful consideration when it comes to the design of structural support elements. One advantage is that water thermal storage is ideal for existing homes, as it’s easier to implement.
The indirect gain technique involves using thermal storage mechanisms between the south-facing windows and their associated rooms. The most popular approach is the use of a Trombe wall, which is an eight to 16-inch thick masonry wall that’s built on the side of the house that faces south.
Heat is absorbed by one or two layers of glass that’s mounted less than an inch in front of a dark-colored wall, which uses its mass to store the heat. During the absorption process, the heat migrates into the home and radiates the living space. Given the thickness of the wall, heat is conveniently transferred inside by sunset when it’s needed most.
Finally, isolated gain commonly involves using a sunspace that can be closed off from the rest of the home. This space can be used as a pleasant living area or to grow plants. They can also provide auxiliary heat. Either of the three functions come with their own compromises and require a number of design considerations.
Opting to use solar and further improving your efficiency with a passive solar design is a wise decision. Focusing on efficiency will help you build a more comfortable, affordable and less impactful living space.