TechPractices: Solar Townhouses, Philadelphia, PA

PATH's Technologies in Practice are large scale housing projects throughout the U.S. where innovative technologies are being installed and used. Information is presented from the viewpoint of builders and remodelers who can use these examples as models for projects of their own.

Summary

How can building with photovoltaics be economical when banks make it so expensive? A builder in Pennsylvania is taking advantage of a new solar mortgage program and coupling it with government grants to make high technology affordable. In a political climate that has warmed up to solar energy, a project that was unthinkable ten years ago is clearing technical and financing hurdles to bring advanced design to homeowners of moderate income.

Details

A private partnership is teaming with the city of Philadelphia and others to offer these 18 affordable townhouses. When Bradley Builders initiated the plan to create the solar townhouses, a low-interest solar financing program became available. Philadelphia saw an opportunity to connect the venture to its homeownership program and pushed for an experienced, comprehensive development team. The team consists of the Department of Energy (DOE), the State Office of Housing and Community Development, Resources for Human Development (a non-profit developer), Crusaders Development Corporation (a non-profit community group), and Bradley Builders and Developers.

Each house will feature a 10:12 pitch, 30-year asphalt-shingle roof and a 6-foot by 16-foot photovoltaic (PV) array with a utility interface, allowing each home to sell extra electricity to the utility company. At 1,400 sf, each PV array will generate 1.4 kw of electricity.

This is how the PV electric supply works: The brain of the system is a grid-interactiveinverter, which constantly analyzes all power draws. If the sun is not shining or loads exceed the capacity of the array, electricity is accepted from the utility. On sunny days where there isn't too much power demand from the house, excess electricity is sent to the utility, effectively spinning the meter backward for energy credit. In this case, the energy credit is about half the market rate for electricity. Electricity is stored in six sealed, non-gaseous lead-acid batteries. The same size as car batteries, they fit in a steel locker in the basement. Because power is supplied only by the utility or the PV panels directly, the batteries are hardly charged-just enough to keep them topped off at 100%, so they last seven to nine years. The batteries also provide approximately two days of backup power in the event of a power failure.

In order to maximize the benefits of the solar strategy, Don Bradley of Bradley Builders emphasized the architectural design as much as the equipment. Large expanses of glass are limited to the south side, and shading techniques prevent overheating. Proper thermal massing reduces energy consumption by absorbing daytime rays and slowly re-radiating it to the spaces overnight.

This project would be pretty impressive with the solar technology alone. But Bradley didn't stop there, including features to further increase energy and construction efficiency. Precast foundation panels enclose the basements, and the thin shell allows for more insulation than conventional foundations. Benefits of optimum value engineering are realized with 2 x 6 framing at 24 inches on center to save lumber while ensuring rigidity and more continuous insulation. Several of the homes are equipped with solar water heating, right alongside the PV panels. And modular construction ensures consistent quality in the whole assembly to keep the homes tight as well as affordable.

Installation/Construction

Before deciding on modular, Bradley looked at conventional stick-built, panelized, and kit-built options. He found modular "5% to 7% more competitive than stick-built," based on rapid site installation, reduced trash cartage, and a more continuous builder/developer relationship. Once the factory learns passive solar framing, there is no need for retraining separate crews in different areas-modules can be shipped throughout the East Coast and to points west.

The modular process allows the site to be prepared while units are assembled in the factory. Each townhouse is composed of six modules, installed by crane. To withstand the stresses of shipping and craning, a triple perimeter band of 2 x 12s wraps the bottom of each module. Each story is composed of a front and rear module, eliminating the problem of mating lines and allowing a full 20' width per house.

Benefits/Costs

The units are inexpensive thanks to a $20,000 HOPE-2 subsidy from the Department of Housing and Urban Development. Can this money be found by other builders? According to Bradley, every city has subsidy programs with HUD money, available if the project meets certain guidelines for the city's low- to moderate-income homeownership program.

The photovoltaics are also on grant. The Department of Energy's PV Bonus program covers 75% of the hard costs of the panels, which would otherwise cost between $9,000 and $10,000 per house for each 1.4 kilowatt array. Because the PV is interactive with the utility, credit from abundant summer sunshine can offset some of the winter electric bills. Total electricity costs are expected to be $300 to $400 per year.

But the real news is the SEIA-GMAC low-interest solar mortgage program. The ability to obtain a competitive mortgage rate for a residential solar installation is a barrier to the use of the technology. Banks are not yet comfortable with solar, and reflect that in the prohibitive front-end costs they charge along with very high interest rates. General Motors Acceptance Corp. (GMAC) Mortgage is the first lender in the country to make residential solar loans at or below commercial rates. The financing program makes it easier for homeowners in several other ways. In addition to the lower interest rates, fees are waived for credit reports, applications, and other front-end costs. And GMAC will stretch qualifying ratios by up to 2%, taking into account increased cash flow due to energy savings, to qualify borrowers for larger loans. GMAC recruited the Solar Energy Industries Association (SEIA) as a partner to help train GMAC loan officers to understand the ins and outs of solar financing.

Code/Regulatory

The modular construction requires a third party inspection service, payed for by the builder and the manufacturer, that verifies the homes are built to code. The inspection service is hired by the Department of Commerce, which regulates the modular industry in Pennsylvania. Solar components and installation must comply with IEEE standards.

Feedback

The units will be sold under standard market conditions-newspaper advertising, promotional brochures, and posters-with extra publicity spurred by groundbreaking and ribbon-cutting ceremonies to which officials show up, in turn attracting local news. Marketing material is being passed along to employees at the University of Pennsylvania; its homeownership program could mesh well with the affordability and low maintenance costs of these homes.

Homeowners will have a maintenance agreement with Bradley, who will educate them on how to use the maintenance-free photovoltaic system. The units will be extensively monitored by DOE for energy consumption to verify proper performance and savings of the various techniques.

Contact(s)

Do you have a specific question? Try the contacts listed below:

Bradley Builders
Temple, PA
215-464-4780