The Emerald Star: Two Years Later
A recent study performed two years after construction of the Ballard residence shows the first Emerald Star Built Green home built in Seattle performs as modeled and in many cases exceeds expectations.
The single-family residence was designed by Caron Architecture and constructed by Dwell Development in 2015 to stringent Built Green Emerald Star standards to achieve net zero energy use and a 70% reduction in water consumption. At that time no other projects existed to provide benchmarks or guidance to assist the design teams, so predictive energy models were developed to project how systems would perform and function.
In 2017, two years after construction was complete, Built Green analyzed the home’s electricity and water consumption to determine if the modeled projections correctly predicted real-world usage. The results demonstrated that the residence not only met net zero electricity usage criteria but also produced more renewable electricity than consumed over a 25-month time period and the excess energy was sold back to Seattle City Light. The residence was able to achieve this outcome with an energy efficient building envelope and an 8kW roof top solar array. As expected, electricity use fluctuated over the course of a year, with most electricity consumed from mid-November to mid-January and the most significant energy electricity were seen from mid-May to mid-July.
Reducing water consumption is also a requirement for the Built Green Emerald Star certification. Built Green established a baseline of 67 gallons of water per person per day based on regional consumption information for this site. The goal is to reduce that consumption baseline by 70% or approximately 20.1 gallons. A 420-gallon cistern was used to capture rainwater for outdoor use, flushing toilets and cold-water laundry. With the aid of the cistern-fed water supply the result over the two-year study showed average water consumption of 19.95 gallons per person.
The third component necessary to be considered a success was owner comfort and experience. The homeowners were given a Likert scale survey to understand if their lifestyle was impacted in any way. The survey verified the owners had a very positive experience living in the home and have since become sustainable living advocates.
Caron Architecture, in partnership with Built Green and Dwell Development, is proud to have been part of this success story. You can view the Built Green white paper, Seattle’s First Emerald Star Home: Two Years Later here.