Harnessing the sun's energy to heat and power a home is more complicated than just putting a couple photovoltaic, better known as solar, panels on the roof and flipping a switch.
"There's not any one thing you need to focus on," said John Mead, founder of McMinnville, Ore.-based Cellar Ridge Custom Homes. "You have to take care of a variety of things through a variety of strategies."
Mead ought to know – he has designed dozens of solar-powered homes in Oregon and Washington. One of his most recent projects, the Solar SMART House, is located in Washougal's Granite Highlands development. Dennis Harvey, the owner of the house, said the design phase took nine months, about 50 percent longer than the design phase for a conventional house, according to Harvey.
Sweet Spot
Site location is one of the most important aspects of designing a solar-powered home, Harvey said. For the SMART house, Harvey chose a lot that had maximum southern exposure, allowing the home to absorb as much solar heat as possible year-round.
A solar home can face no more than 15 degrees from due south, according to Timothy Buckley, a principle at Greenstone Architecture PLLC, a Vancouver firm focused on projects certified by the Leadership in Energy and Environmental design.
An architect for the Felida Living House, another solar home project in Clark County, Buckley uses a solar pathfinder device to help determine an optimal building site.
However, conditions at a solar home building site can be far from perfect. For example, the Washougal SMART house's 10 corners and differing setbacks presented designer Mead with a challenge – fitting the one-story, rectangular building on the lot so that it faced the correct direction.
Builders should look to the future when selecting a site for a solar home, asking themselves how the landscape might change or what structures might be built that could affect access to the sun's energy.
Less Is More
Once the site and orientation is set, Mead said, the next challenge in designing a solar home is to build the house efficiently to minimize the home's energy needs.
"For solar to work," Buckley said. "We need to drastically reduce the energy consumed."
The first step to achieving energy efficiency is to reduce square footage. Mead said a solar house should be between 2,500 and 2,700 square feet and be rectangular in design. A smaller house needs less heating – heating/cooling accounts for somewhere between 42 to 47 percent of a home's energy use.
Next, every aspect of the house must be designed to be as energy efficient as possible. And that means increasing the insulative value of the floor, walls, roof and windows to reduce air infiltration and heat loss.
For example, Harvey's home is built on a solid slab of concrete to provide thermal mass (absorbs heat during the day, slowly releases it at night). The walls are structured insulated panels, which are wood sheeting filled with foam and provide more than twice the R-value – a measure of thermal resistance used in the building and construction industry – than standard wall fiberglass batts.
"Fiberglass batts are not very efficient," Buckley said, "And wood is a terrible insulator." Buckley believes we will see more home design to avoid heat loss, such as staggered stud construction, insulated concrete structures and rigid insulation on the exterior of buildings.
Taking advantage of natural light, using energy-efficient lighting and appliances and using solar energy to heat the house's water are other ways to reduce a solar home's energy requirements – all of which Harvey's SMART house does.
Landscaping, too, is important. Buckley said that solar home designers should choose trees that drop their leaves at the right time in the winter. Conifers, which provide shade even in the winter, are a poor choice for solar home landscaping. Harvey will also use native plantings instead of lawn to reduce the need for water.
Many of the above strategies, plus others, are required to meet LEED-platinum certification, the highest awarded, which is Harvey's goal. When complete in September, his house will be one of only six such certified homes in Washington state.
What's the Plan, Stan?
According to Mead, the floor plan is a big element in solar design. About 26 percent of a home's heat is lost through windows. For a solar home, 60 to 70 percent of the windows should face south, as well as featuring the correct type of glazing to minimize heat loss. Common spaces, such as the kitchen, dining room and living room should be kept to the south, so they have the most light during the winter as possible. Seldom-used rooms, such as bathrooms and utility rooms, and the garage, can be tucked off to the north side of the house.
Buckley added that people's lifestyles can also affect the placement of rooms. For example, early risers may want their bedroom facing east, while late sleepers might prefer a north-facing bedroom.
Roof and eave angles, too, must be carefully calculated.
"You have to look at the solar angles at different times of the year and do the geometry, so that the eave is at the correct aspect with the window," Mead said. This allows the window to be shaded in the summer, but allow full light in the winter.
The roof angle also must allow for the greatest absorption of solar energy. Harvey said for his house, the optimum roof angle was 30 degrees.
Some people may not think designing the smallest house possible and reducing energy consumption by as much as possible sounds very exciting – but it's the key to good solar home design.
"You have to eat your conservation veggies before you get your solar dessert," Mead said.
Blowin' in the Wind
Dennis Harvey's Solar SMART House will also use wind energy. While using wind-generated power doesn't affect the design of the home as much as solar power, there are some important considerations.
As with solar, site selection is paramount.
"You need a clear, unobstructed wind path," said Timothy Buckley, principal of Greenstone Architecture, PLLC. "And the towers need to be above trees or other obstacles."
Buckley suggested using GPS-based wind maps to find the best location for a tower.
CC&Rs can also be a concern. Harvey said one of the five concessions he won from the Granite Highlands developer was permission to erect a 33-foot wind tower on his lot – just sneaking in under Washougal's 35-foot height limit. The tower is located 45 feet from the house, and will use a three-blade turbine to harvest the lot's 7 to 11 mph average wind.
Financial Advantages
Homeowner Dennis Harvey's solar and wind set-up will be "grid-tied," which means he can sell kilowatt hours (kWh) back to Clark Public Utilities when his system is producing more energy than his house needs. Mick Shutt, a spokesman for Clark Public Utilities said they had 18 customers who are currently selling power back to the grid; According to Harvey, the SMART house is the first grid-tied system for Clark Public Utilities that features both solar and wind power.
The current cost of a kWh in Clark County is 7.65 cents; according to Shutt, Harvey will be able to sell his extra energy (solar- or wind-generated) back to the Clark Public Utilities at the current rate of 7.3 cents/kWh.
Harvey will also benefit from several other incentives:
- The State of Washington offers a financial incentive of up to $2,000 per year to people who install renewable energy systems (like wind and solar) at their homes.
- Washington state also offers sales tax exemption for the purchase and installation of solar hot water systems, wind generators and photovoltaic systems
- A 30 percent federal tax credit is available (up to $2,000) for total materials and labor for solar hot water systems, wind generators and photovoltaic systems
- Clark Public Utilities offers a $1,000 direct rebate for using a solar hot water system with an electric water heater.
Harvey estimates his projected financial payback for his solar and wind systems will be seven to nine years.
