Revisiting ‘Homes of the Future’
Rainwater system prompts LEED Platinum Certification
In 1933, the Tennessee Valley Authority (TVA) constructed a model community, Norris, Tennessee, as part of the Norris Dam project. The series of small homes served as the archetype for modern and efficient living in that time period. Over the course of the last two-and-a-half years, 50 University of Tennessee-Knoxville students have been reviving the spirit of the old town by building the new Norris House.
“The project began in fall of 2008 to commemorate the TVA’s 75th anniversary and is a 21st century reinterpretation of the original series of Norris homes,” said research specialist and UTK architectural alumnus, Samuel Mortimer.
The Norris House is the largest design/build project ever conducted by UTK students. The home aspires to become one of only seven certified LEED Platinum homes in Tennessee. To accomplish this rating, many factors come together, lending to the project’s resolved focus on sustainability.
“As unique and ingenious as the whole project is, the heart and soul is the Brae rainwater collection system,” said Scott Robinson, owner of Scott’s Plumbing in Knoxville.
“About 80 percent of the roof’s surface area is used to collect rainwater,” said Mortimer.
From the roof, the water goes through a series of pre-filters before entering an above- ground, 400-gallon storage tank. When the “house tank” reaches capacity, overflow runs into a 200-gallon tank below the garden. The garden tank is equipped with a hand pump to supply water to the landscape and a vegetable garden sized to grow enough produce for two people.
The average annual rainfall on campus is 54 inches per year. At that rate, and with the roof area that feeds the catchment tanks, the system collects nearly 21,000 gallons annually. With water saving fixtures, calculations show that, with two inhabitants, annual water use for the home is 16,500 gallons, well below the harvesting system’s capability.
According to Robinson, the system that was installed during the home’s construction — technology supplied by BRAE, a Watts Water Technologies subsidiary — harvests more rainwater than Norris House occupants typically use. Scott’s Plumbing, with the help of the UTK team, also installed portions of the home’s plumbing system, a domestic water solar thermal panel and a greywater distribution system. The way the system is set up, rainfall usually exceeds the use of stored rainwater and simply flows out onto a terraced spillway, watering the gardens.
The spillway is made up of five multilevel flower beds, each containing hearty local plant species. “Landscape architecture majors helped design the overflow beds,” said Mortimer. “They carefully selected plant species that can not only handle being inundated with water but also thrive in a drought-like condition.”
“It’s very important to keep the greywater from entering the sterile city water,” said Robinson. “The students worked to shed light on the safety of using a greywater distribution system as well as a rain collection system. The town of Norris was rightfully concerned about greywater entering the landscape.”
Since the greywater system is experimental, both the city of Norris and the design team wanted a fail-safe alternative so, with the flip of a valve, the system can be easily diverted to serve the city sewer.
Norris House greywater is collected from the bathroom sink, shower and washing machine. It is piped underground and enters the landscape through a perforated canister buried in a large bed of mulch and soil. The bed is sized to hold approximately 150 gallons of greywater before saturating and is also planted with native plants that were selected based on anticipated greywater volume.
“The UTK team worked closely with the Tennessee Department of Conservation and the Norris Water Commission to ensure health and safety,” said College of Architecture and Design assistant professor Tricia Stuth. “The city manager worked on ordinance revisions that were ultimately passed by the city council. The building permit allows systems to operate for one year, under the oversight of the UTK team, and data collected will be used to support making the temporary permits permanent.”
The 768-square-foot home will provide verifiable technical data to demonstrate the viability of residential rainwater collection and use. The project was initiated as an entry into the EPA’s People Prosperity and the Planet (P3) competition, a national competition that encourages students to propose “solutions to real world challenges involving the overall sustainability of human society.”
The first of four phases was a research and design period, funded by a $10,000 grant from the EPA. Ultimately, UTK’s team was chosen as one of six winners from among 40 teams, and the EPA granted $75,000 to the project.
In phase two, students began their collaboration with Clayton Homes, manufacturer of modular homes. Together, they established goals, targeting a LEED for Homes Platinum rating. Some students collaborated with Clayton Homes during the design phase. Others prepared the physical site in Norris. Another team began work on various components of the building’s interior for later installation. During the fall 2010 semester, phase three construction began.
“The students always bring a fresh perspective to things that we do every day,” said Andy Hutsell, Clayton Homes designer. “They’re passionate about their work, and they’ll be much better equipped when they go out into the world because of the Norris House experience.”
Now, in the midst of the “demonstration and evaluation” phase, the college’s chair of the Master of Landscape Architecture program and his wife will live in the home. Energy consumption, temperature, relative humidity, water use and water quality will be measured. At the end of the evaluation period, the home will be up for sale; proceeds will be used as seed money for the next project.
From the standing seam alloy roof to the reclaimed oak flooring, the home is a prime example of what LEED construction should be. With a super-tight, heavily insulated building envelope, the structure loses very little energy to the outside world. Every square inch that could be insulated, was insulated. Foundation block cores were filled with Perilite as the building footprint started to take shape. Inside the foundation walls, two inches of rigid insulation was used, and the foundation rim was sprayed with Icynene.
“We decided to use advanced framing techniques, which results in a 17 percent reduction in lumber and substantially more insulation,” said Mortimer. The 24-inch stud bays are filled with thick batting insulation. On the outside of the walls, one-inch rigid insulation curbs any thermal bridging across the two-by-six studs. The ceiling rafter bays and gable ends were also filled with batting insulation, and sheets of half-inch rigid insulation were hung before the drywall was installed. The outside of the building is clad with Atlantic white cedar. Double-pane, low-E coated, argon-filled windows also limit energy transfer.
“We calculated the home’s heat loss at 17,442 Btu,” said Mortimer, “or 19.5 Btu per square foot. The blower door test yielded .04 ACH, the lowest score ever verified by our green-rater.”
A four-by-eight foot Enerworks solar-thermal panel on the roof supplies hot water to an 80-gallon tank in the home. A 1.5 gpm electric instantaneous water heater supplements the solar-heater water when necessary.
Heating and cooling the home is achieved through the use of a multiple-head mini split system. The building has one traditional bedroom as the first zone, a “swing space” that can be used as a second bedroom and a kitchen. Each of the three zones calls for a separate air handler; all are connected to a single, multi-zone condensing unit. As an addition to the HVAC system, the new Norris House has an energy recovery ventilation (ERV) system in the sealed crawlspace under the building. Depending on the season, the ERV either pre-cools or pre-warms incoming fresh air.
Throughout the project, goals set by the student team were consistently met. “UTK has never done anything like this before, especially on this scale” said Mortimer.
“The Norris House project was real-life work experience that’s invaluable to the students who’ve been involved,” said Mary French, a College of Engineering grad student. “I’m really glad I had the opportunity to participate.”
Watts also supplied a complete reverse osmosis system for the New Norris House project. Only recently installed, treated water is still undergoing testing. Potable water from the rainwater harvesting system is the goal.