Using passive solar heating to reduce energy usage

May 17, 2016

From photovoltaic solar cells to smart window films, the energy efficiency industry has been driven forward by product innovation. That being said, some of the most impactful efficient building strategies are not technologically-based at all, but improve energy usage through design alone. Passive solar heating, for example, can provide large buildings the heat they need at a fraction of the cost of advanced HVAC or active solar heating systems. 

Passive solar heating relies on south-facing windows optimized to collect sunlight during cooler, winter months. When the light enters a building, it is captured and stored as thermal energy in the building materials themselves. As the sun goes down and temperatures begin to fall, this energy is naturally released back into the living space, providing heat at no cost or inconvenience to the user. 

"Passive solar heating is inexpensive and can save energy costs in the long term."

Optimizing for passive solar heating
Equipping a building to take advantage of passive solar heating is relatively inexpensive but can save owners on their energy costs in the long term. To maximize this investment, designers can use building materials with a high heat capacity, known as "thermal mass," to store the sun's energy. Some of the most effective materials include brick and concrete for interior walls, as well as tile and stone flooring. 

Plus, roof overhangs can help block out unwanted sunlight during hot summer months while allowing the sun's rays into the building in the winter. They work by limiting the angle of sunlight that can reach the windows: winter's shallow angles go unimpeded while light from summer's high sun is blocked before reaching the window. With these controls, passive solar design can reduce the energy load required to cool a building during the summer, as well as that needed to heat it in the winter. 

Benefits of passive solar heating
First and foremost, these relatively simple strategies can have a massive effect on a building's energy performance. According to the National Institute of Building Sciences, even minor levels of passive solar heating can reduce building heating requirements by as much as 25 percent, with only low incremental cost required to implement the simple strategies. Even the most aggressive passive solar heating systems require a relatively small up-front investment, but can reduce heating energy use by as much as 75 percent, reports the NIBS.

In addition to reducing energy costs, buildings designed with passive solar heat in mind are often more comfortable. South-facing windows allow in a considerable amount of daylight, improving satisfaction and user productivity. Plus, they manage to maintain a more stable temperature, even after the sun goes down. Finally, the energy-saving methods at work in passive solar design do not generate greenhouse gasses and can help slow fossil fuel depletion.