Is it possible to build an affordable net -zero home in Bellingham? That was the question first posed when Kulshan Community Land Trust (KCLT) and Cascade Joinery teamed up back in 2009 to build KCLT’s 100th permanently affordable home in Whatcom County.
What exactly is a net -zero home? Simply put it is a home designed to produce enough energy on site to satisfy its annual energy consumption requirements. The program given to me as architect was to design a 2-3 bedroom home under 1200 square feet and built for no more than $160,000. Achieving net-zero energy use within this framework was a significant challenge requiring careful analysis of each and every decision in order to balance energy efficiency and affordability.
So what does it take to achieve net -zero energy use? Net zero energy use is achieved through the combination of passive design, energy efficient construction, homeowner conservation, and on-site production of renewable energy as described below:
Passive Design measures are low cost solutions that take advantage of the energy the sun freely gives us. This involves a careful site study and sometimes computer modeling to determine the proper building orientation, optimal amount, size, and location of glazing, thermal mass and shading devices all with the goal of maximizing and storing solar heat gain, minimizing heat loss, and preventing overheating. Passive design also means designing smaller homes that use less energy from the start.
Energy Efficient Construction will get you closer to net zero energy use than any other thing you can do. A highly insulated, tightly sealed envelope with maximum efficiency appliances and lighting is critical in order to reduce consumption. In the Madrona street house advanced framing, high insulation values, and careful detailing to minimize infiltration are critical components of the design. Additionally infiltration rates were verified via blower door tests at various stages during construction in order to measure performance while corrections could still be made.
Homeowner Conservation is the cheapest form of energy. As simple as closing the refrigerator door and turning out the lights. Education and providing the tools to monitor real time energy usage is the first step toward achieving net-zero energy usage.
On Site Renewable Energy is the final step toward net-zero energy use after passive design, energy efficient construction, and conservation measures have been exhausted. Renewable energy technology is still the most expensive piece of the puzzle thereforereducing overall consumption is critical in order to reduce the size of whatever renewable energy system you choose, be it wind or solar power. In the KCLT home the solar panels were provided by an anonymous donor. Here in the Pacific Northwest producing solar energy is made possible by net-metering. Net-metering means that the surplus of power that your photovoltaic system will produce during the long summer days is sold back to the power company and those credits are applied to you during the winter months when your system will produce less and you may have to purchase power.
So will this house achieve net-zero? The energy modeling software used to design this home tells us that we may be very close. It will take at least a year of occupancy to find out for sure. Fortunately the homeowners are educated about the goal and committed to pursuing it. The most advanced energy efficient materials, systems, and technologies have not been applied to this home because affordability was an equally important goal. That is what makes this home so compelling. It is the attempt to balance these two competing goals that will move our community closer to the dream of permanently affordable homes that produce as much energy as the consume, provide healthy indoor environments and use the planets resources responsibly.