Passive House Community Utilizes HRVs to Optimize IAQ
Heat recovery ventilation systems maintain healthy indoor air
BELFAST, Maine — After years of planning, design, and construction, Belfast Cohousing & Ecovillage is complete. This 36-unit multi-generational community, located on 42 acres, has a mission to be an innovative housing model for rural Maine. The ultra-energy-efficient homes, pedestrian-friendly layout, shared common house, and preservation of land for agricultural purposes make this community a noteworthy example of environmental sustainability.
All of the homes were built to the passive house standard: they use 90 percent less energy to heat and cool than a typical code-built home. All feature triple-pane windows and doors, air-tight sealing, generous amounts of insulation, and a solar orientation for passive heat gain. To maintain healthy IAQ, each home and the common house are equipped with a Zehnder heat recovery ventilation (HRV) system.
Zehnder HRVs and energy recovery ventilators (ERVs) are balanced systems that both remove stale air and provide a constant supply of fresh, filtered air into living areas (i.e., bedrooms and the living room) to ensure optimal air circulation throughout the house. By controlling the location of the fresh-air intake, the ventilation systems can eliminate unfiltered make-up air and moisture intake from wall cracks and window frames, which can be problematic in negatively pressured homes relying only on kitchen and bathroom exhaust fans for ventilation. Belfast Cohousing & Ecovillage members are using HEPA-grade filters in their Zehnder HRVs to remove dust, pollen, and other pollutants from the incoming fresh air.
Hans-Peter Zehnder, chairman and fourth generation owner of the Zehnder Group, and David Chouvelon, vice president of the Zehnder America business unit, recently toured Belfast Cohousing & Ecovillage as part of a Northeast tour of Zehnder customers and installed projects.
“This Ecovillage is an illustration that Zehnder systems are clearly valuable in many different types of projects, from a Habitat for Humanity project in River Falls, Wisconsin, to various cohousing communities, to New York City apartment buildings,” said Zehnder. “It is great to see our products being used on more affordable applications and to serve as a model for other builders to follow.”
The Ecovillage homes only use electricity for space and water heating, allowing renewable energy to power the homes. To date, 22 of the 36 homes are near net zero, with solar energy producing all or most of the power. Zehnder HRVs allow the homes to be both energy efficient and well ventilated because they capture up to 90 percent of the heat from the exhaust air before it leaves the home, said the company.
During cold weather, the HRV units pre-warm incoming air from the exhaust air, reducing heating bills. During warm weather, the systems keep the homes cooler by reducing the temperature of the fresh intake air. This also helps eliminate the need for air conditioning systems. Switches in the bathrooms and kitchen let occupants boost the ventilation system after showering or cooking.
The Belfast Cohousing & Ecovillage common house is used for several community meals a week and contains a large dining room, kitchen, guest bedroom, children’s playroom, and root cellar. This 4,000-square-foot structure is equipped with two HRVs to make it more adaptive to the varying levels of use that are typical for this building.
Data from a carbon dioxide sensor in the large dining room determines when the HRV for that room will ramp up into a higher mode. Because carbon dioxide levels correspond with building use, the system will circulate more fresh air during times of greater occupancy. The system that ventilates the remainder of the common house can be boosted using a convenient switch.
“The design of the ventilation system in the common house in particular is a good example of the system engineering knowledge that we provide with our solutions,” said Chouvelon. “It is not only the high performance of the Zehnder HRV and ERV units that sets our company apart, but also the design work with dedicated air distribution components and silencers.”
The Zehnder systems throughout the community were installed by GOLogic, the design-build firm that served as the general contractor for Belfast Cohousing & Ecovillage. Zehnder America provided guidance and ventilation expertise throughout the project.
All 36 units in Belfast Cohousing & Ecovillage are occupied, and community members are working on a variety of projects, including an on-site organic worker-share farm and increased use of on-site renewable energy.
For more information, visit http://zehnderamerica.com.
Publication date: 6/6/2016