How Passive Solar Energy Works

How Passive Solar Energy Works

Passive solar energy is the collection and effective use of the sun’s heat to reduce the need for auxiliary heating in homes or buildings. This process uses various design features and materials to heat a home or business during colder months.

The process of passive solar energy involves three steps: collecting, storing, and distributing solar heat. Working as a team, these components enable a building to retain heat while reducing its reliance on auxiliary heating systems like furnaces or boilers.

With careful planning, almost any home can be built with passive solar technology. Read on to learn more about passive solar energy and its potential in your future home.

What is Passive Solar Energy?

The sun’s rays can be used to warm homes passively by reflecting the light from the sun in through windows, allowing it to heat a house, and then keeping it inside as long as possible by maximizing insulation.

While it can seem like a magic trick for keeping warm during cold months, it’s actually a fairly simple process. To understand how it works, it’s helpful to break the process into 3 stages. First, solar energy is collected by a home’s materials and architectural features. Next, the energy is stored in the building’s thermal mass (usually the ground). Finally, the thermal energy is distributed to the home’s living spaces.

How Does Passive Solar Work?

A key component of passive solar is the use of south-facing windows. During the fall and spring, windows on the southern side of a building gather solar energy during daylight hours.

The collected solar energy is then stored in a home’s thermal mass, like walls, floors and ceilings. This thermal mass is usually made of concrete or masonry materials, but can also include heavy furniture and large bookshelves.

When the sun goes down, the thermal mass continues to store the collected energy. Then, during the winter, the stored solar energy is then distributed to the living spaces of the house by way of insulation and fans.

Installing Windows for Passive Solar Energy

The most visible element of passive solar design is the use of large, south-facing windows. In order to maximize the amount of solar energy collected through windows, it’s important to choose the right materials.

Passive solar designers recommend using high-quality glass with a high Solar Heat Gain Coefficient (SHGC). Glass with a high SHGC will be more opaque, preventing the collected solar energy from escaping. Beyond the type of glass used, it’s also important to consider window placement.

Passive solar designers recommend positioning windows on the southern side of a building. That said, it’s important to note that southern-facing windows aren’t necessary for passive solar design. Instead, designers recommend positioning the windows so that they’re perpendicular to the sun’s path during fall and spring. This will maximize the amount of solar energy collected.

Installing Shading Elements for Passive Solar Energy

While large windows are a key component of passive solar design, it’s important to note that too much sunlight is also a problem. In order to prevent overheating, buildings designed for passive solar energy use two types of shading.

Shade trees are an obvious choice for blocking sunlight. But, there are also a variety of other ways to reduce light entering a home. For example, installing awnings, roller shades, or shades designed to retract at certain times can help reduce the amount of sunlight entering a building. Alternatively, curtains and blinds can be used to block out the sun at certain times.

Installing Walls for Passive Solar Energy

Even when it’s not being used to collect and store solar energy, a wall can be an essential component of passive solar design. In order to collect and store the most solar energy possible, designers recommend building walls that are at least 16 inches thick.

When used for passive solar design, these thick walls are referred to as thermal mass. When used for passive solar design, thermal mass is placed at least two feet from the outer perimeter of the building. This prevents collected solar energy from escaping too quickly.

Installing a Roof for Passive Solar Energy

In addition to collecting solar energy through walls, a roof can also be used to collect solar energy. However, roofs are only useful for passive solar design when they are made of a material that can retain the collected heat.

Indeed, there are a few materials that work best for passive solar energy collection. These include metal and thick, dark-colored shingles or tiles. Metal roofs are particularly effective. That’s because metal is a good conductor of heat and can also reflect sunlight. But, before installing a metal roof, it’s important to take nearby trees, vines, and other obstacles into consideration. Though metal roofs are great for passive solar energy, they’re also very difficult to clean.

Key Takeaway

The best way to collect solar energy is through large, south-facing windows made from high-quality glass. When placed perpendicular to the sun’s path, these windows will collect solar energy during fall and spring.

Additionally, it’s important to consider the placement of walls and a roof when designing for passive solar energy because they will also be used to store the solar energy. Keep in mind that every home is different and has unique needs. While passive solar energy is an excellent way to reduce the amount of energy used for heating, it isn’t a one-size-fits-all solution. That’s why it’s important to consult with a solar design professional to identify the best course of action for your home.


About the Author: Julie Souza