As the cost of photovoltaic (PV) solar panels continues to fall, and the impacts of climate change continue to alarm, we find more homeowners pursuing Zero Net Energy (ZNE) homes, with many options for getting there. The trick is to understand a home’s energy demands upfront, to make sure there is adequate area for the PVs, and to improve energy efficiency, which helps keep the PV system ‘right-sized’.
Our team recently toured an exemplary ZNE project, the Cal Poly Solar Decathlon House. Designed by students to compete in the Solar Decathlon competition in Irvine, the house is optimized for efficiency, including Structural Insulating Panels (SIP’s), strategic shading, high performance windows, LED lighting and an innovative mechanical system that includes a phase-change material in the duct work, which facilitates night venting without the weight of traditional thermal mass. Even though the home is small, the PV system is over 8 kW, covering most of the roof and patio. The reason the system is so big? It also has to charge an electric car, and the car could use half of the electricity generated!
Touring the Cal Poly Solar Decathlon house, with instructors Rich Beller and Sandy Stannard.
More traditional homes can be ZNE as well. For a 2,000 SF home, you might want a 4 kW to 6 kW size system and up to 600 SF of clear roof area. Of course, the more energy you use, not just heating and cooling but also for appliances and vehicles, the more PVs you will need. Small urban homes use less energy, but also have less roof area and often less land to locate PVs, so efficiency becomes more critical.
Thankfully, consumer demand and energy codes are driving efficient, affordable mechanical systems, lighting, and appliances. Combine that with passive thermal strategies incorporated into beautiful design, and ZNE becomes absolutely achievable!
In Balance Green Consulting is proud to have provided energy consulting and Title 24 services for Cal Poly’s Solar Decathlon home. The project took third place overall! For more on the project, or to become a sponsor, visit Cal Poly’s Solar.
Are you thinking of pursuing a zero net-energy project? Contact us to find out how we can help you achieve your energy and water efficiency goals.