What is passive solar design, and how does it work? | News

Jeffrey Lucas, a local architect, says he’s saved $60,000 on utility bills over 30 years after incorporating passive solar design at his Johnson City home.

Those savings, he stressed, are after taxes.

Lucas has been implementing improvements at his house in phases since the 1990s, which has included super-insulating the building and installing Marvin windows with a high resistance factor to keep cold out in the winter and heat out in the summer.

“We gutted this thing,” he said, sitting on the patio behind his house on a sunny but chilly February day.

What is passive solar?

According to the U.S. Department of Energy, passive solar homes take advantage of a building’s site, climate and materials to minimize energy use. They collect heat as the sun shines through properly oriented windows and retain it in materials that store heat.

“Passive is just taking advantage of the sun’s energy and helping to heat the building,” said Paul Sims, a professor in the ETSU Department of Engineering, Engineering Technology and Surveying. “It’s got so many forms that you can take with it that there’s not just one definition of a passive solar heating system.”

The university, for example, has a large passive solar installation at the top of the ETSU Center for Physical Activity, which helps heat the facility.

“It basically collects the heat from the sun using these passive solar collectors on the roof,” Sims said. “This directs the energy back into the building. The only thing moving on it is a fan, which pulls the air through the collectors to deposit it in the building.”

There are essentially two types of solar design, Sims noted: Active and passive.

Passive building for homes can include many different things, Sims said, such as a water recirculation system on the roof that heats water using the sun’s rays. It can also be a way to design a house.

Active solar systems, such as solar panels, typically store energy in a battery network, which a house pulls as needed. If the system generates more than the homeowner needs, some utilities will allow residents to put the energy back into the grid. Some buildings even use both passive and active solar attributes.

Sims said the nice thing about active systems is that, although they’re typically installed on a roof, a solar panel array or wind turbine can be set a distance from the home.

“There’s options with that, but if you look at passive, passive needs to be fairly colocated with the facility in which it’s being used in,” Sims said.

The university wouldn’t, for example, be able to move its passive arrays too far from the CPA because there would be too much energy loss and cost in transporting the air back to the building to heat it.

How common is passive solar?

Sims said he knows of a local homebuilder who is working on LEED-certified mobile homes, which includes incorporating high insulation and reduced water utilization.

“It’s optimized for energy savings,” Sims said. “In a way, it’s not passive as we’d say, but it has reduced the overall cost.”

Sims said homes are now starting to be designed with higher levels of insulation, reduced water use and more efficient ways to heat hot water.

“That’s become very common,” he said.

At the same time, Sims said, he’s not familiar with contractors in the region who specialize in passive solar home design or construction.

What would it take to make passive solar architecture a more mainstream design philosophy?

Education, said Lucas.

“You’ve got to educate people that this is the best way to do it,” he said. “That this is the cost effective way to build. We’re terribly wasteful in America. We build for 20 years instead of 50 or 100.”

If people are trying to reduce their energy footprint, Sims said, the simplest thing they can do is turn their thermostat down and avoid wasting water.

In this region, people pay low energy costs compared to residents elsewhere because of the Tennessee Valley Authority, Sims said.

“Our cost per kilowatt is a bargain here,” Sims said. “And this may be why you don’t see as many people adopting these types of things as you might imagine. … It’s hard to justify going in and making say $8,000 worth of changes which are going to take a long period of time to recover unless you just want to do something for the environment.”