Boulder ZED-3, the latest offering from Boulder Zero Energy Development, is a new home targeting LEED Platinum and Passive House Certification in central Boulder. Anticipating the future of neighborhood and sustainable home design, this project utilizes existing foundation, plumbing and electrical infrastructure to transform a post-war era single story ranch home into a contemporary, solar powered, 2-story home with the latest technology.
The project achieves its extreme energy savings through many strategies, but primarily via a super insulated building envelope.
Walls with 4″ of exterior continuous insulation keep occupants cool in the summer and warm in the winter. Super insulated triple pane windows are tuned to the orientation with special coatings. East and West windows reject solar heat, while south windows are specified to provide high solar heat gain in the winter. During the summer months, simple horizontal roof overhangs keep the direct rays out – the basics of passive solar design. Roofs are also super insulated with deep cavity insulation and continuous insulation to break the thermal bridging. The existing crawlspace was the most challenging part to insulate to passive house levels, with on-grade insulation over a new radon mitigation system and continuous interior wall insulation.
Also critical to the drastic energy savings of the passive house methodology is air sealing. Achieving the .6 ACH50 result requires a continuous air barrier over the entire building shell, keeping unwanted infiltration from building cavities out of the indoor air. Filtered, fresh air is brought in during cold winter months with a sophisticated but an easy to use and maintain energy recovery ventilation system. This ventilation system provides superior indoor air quality in every room, constantly exhausting stale air from kitchens, bathrooms and laundry spaces, and providing fresh air to living and sleeping rooms. With super efficient fans and engineered and field inspected and tested ducting systems, this system delivers the designed air flow to each space while recovering around 90% of the energy inside the house (obviously much more efficient and easier than trying to open windows in the winter). During the summer, this system can be shut down and windows open, or during the few weeks in Boulder where it gets too warm outside, it can be used the keep the cool air in and the hot air out. The system not only recycles heat, but also humidity to keep the indoor air comfortable by using the recovered humidity from inside the house, all while providing constant, fresh air for the occupants.
With such efficient envelope and ventilation systems rarely seen in even high end homes, only a very small mechanical system is required to achieve superior comfort in every room of the house. In fact, the heating and cooling systems are roughly 10 times smaller. With this micro-conditioning comfort system, only a small amount heating and cooling is needed for superior comfort, compared to a typical house with a lot of hot air blowing around, the ZED3 system is quiet and nearly inVisible.
Seeking a LEED Platinum rating as well as Passive House certification, the home incorporates an innovative integrated approach design, focuses on conscious selection of materials and resources, energy-wise strategies, water efficiency, and indoor air quality among other concepts.
Integrating Passive House design principles, the home strives to stay comfortable in the event of a power outage for passive survivability and low future cost of mechanical system maintenance or upgrade, given the small size of the loads. A 6kW photovoltaic system covers the home’s reduced heat demand and super efficient lighting package.
Landscape designed to handle all roof runoff in rain gardens and bioswales, minimizing the building’s impact on local waterways.
Pictures by: Dane Cronin Photography and fuentesdesign