Prefab House is Living Lab for Energy and Water Conservation
LEED Platinum-certified prefab cottage features a compact footprint, careful siting, and local natural materials.
Built in 1933, the Tennessee Valley Authority’s model community of Norris, Tenn., showcased simple, prefabricated houses equipped with modern amenities such as electricity, heating, and indoor plumbing that were rare in Appalachia at the time.
More than 75 years later in the same community, the New Norris House adheres to the development’s founding principles of affordable sustainable living. It too is a test case for innovative building systems and techniques, but instead of promoting the use of resources, the 1,006-square-foot prefab cottage is focused on conservation and self-reliance.
Certified to and exceeding LEED-Platinum standards by 30 percent, the project works with natural resources such as sunlight and rainwater to reduce its environmental footprint. It uses no fossil fuels, thanks to the TVA’s hydropower dams, and uses 50 percent less energy than similar-sized homes in the area.
The project team for the live-in demonstration home was made up of students and faculty from the University of Tennessee-Knoxville College of Architecture + Design, who incorporated passive solar design and ventilation to help the structure maintain comfortable interior temperatures even during the area’s hot and humid summers. Natural daylighting via doors, windows, and skylights provides basic illumination needs and tactics such as a large retractable awning on the southern façade control solar heat gain in summer and exploit it in winter. A solar hot water panel provides most of the hot water needs; a small tankless electric water heater boosts stored hot water temperatures when needed.
Thanks to experimental permits from state and local governments, project planners were able to explore the use of rainwater and graywater for use inside and outside the home, tactics that are prohibited in nearly all of the country. About 85 percent of roof runoff is used for toilet flushing, clothes washing, and irrigation, and all graywater (except from the kitchen sink) is sent outdoors for treatment in a specially designed graywater infiltration bed.
Water samples are collected regularly for lab testing in order to inform future water treatment policies and codes. Water data will be used by to reform residential rainwater use and graywater regulations.
The super-insulated envelope (R-24 foundation, R-29 walls, and R-42 roof), facilitates .04 natural air change per hour, and includes a ventilated rain screen façade that resists moisture and durable, locally sourced Atlantic white cedar. Other sustainable features include:
–99 percent permeable surfaces
–Low-E, argon-filled windows and skylights with a U-Factor of 0.24 and SHGC of 0.27
–A location within a half-mile walk or bike ride to schools, shops, and restaurants
–Cabinets made with urea formaldehyde-free plywood and MDF and finished with low-VOC paint
–A Powerhouse Dynamics eMonitor24 Energy Management Solution electrical monitoring system
— A standing seam metal roof made of 99 percent recycled material with a Galvalume finish with a 54.5 Solar Reflectivity Index (SRI)
–Fifty-two digital sensors that monitor occupancy patterns throughout the home.
Data collected includes overall and specific energy use, water use, rainfall, solar water temperatures, and solar radiance. The results can be viewed at the New Norris House blog.