John Wesley Miller Companies, a Building America partner and renowned Tucson-area builder, has earned Tucson Electric Power’s first heating and cooling guarantee for a home remodel.
Miller overhauled a 47-year-old, 2,000-square-foot adobe home, dramatically improving its energy performance and slashing heating and cooling costs by 75%.
Under Tucson Electric Power’s utility guarantee program, this home is guaranteed to have heating or cooling bills for five years that do not exceed $1.26 a day (on average), which demonstrates significant efficiency in a climate where the average summer temperature is 100 F.
“We modeled all of our remodeling [at this home] after what we have done at our Armory Park Del Sol development in Tucson,” says Miller. At Armory Park, Miller teamed with the U.S. Department of Energy and its Building America teams to design a development of highly efficient solar homes, including one of the first true zero-energy homes in the country.
The remodeled burnt adobe home at 3002 East Hawthorne Street is located near the University of Arizona in the Sam Hughes area, which is a neighborhood listed on the National Register of Historic Places. When remodeled, the three-bedroom, two-bathroom home kept the original home footprint with the exception of a new two-car garage. Miller said that the remodeled home reaches energy savings of 66% to 75% compared with the original.
Miller had two personal motivations for purchasing and remodeling the house. “House building is dead, and I want to keep my guys busy,” he says. “We have a very specialized crew of subcontractors and our own people. I have another bias: It is only a block and a half from where I live. The home has been rented to university students for 10–15 years. It was a real eye sore. In all respects—environmentally, property values, historical character—it was an opportunity to turn this house around completely.”
Miller believes that by beginning with improvements to the building envelope, that you reduce the need for energy significantly.
“We started with an old adobe house that was very energy inefficient. The biggest thing we did was to put the insulation on the outside of the adobe so that the masonry structure becomes a storage system for the warmth and the cold,” says Miller.
The home’s thick adobe walls had thermal mass storage and conduction properties that could be controlled with the external insulation. The house was wrapped with rigid foil-faced 1½” polyisocyanurate board that was applied directly to the outside surface of the adobe. This rigid foam sheathing was extended down the wall to insulate the edge of the slab. The board was covered with a three-coat stucco finish to seal the wall and restore the adobe appearance. The brick parapet was left exposed as an architectural detail.
For the flat roof assembly, the original roofing was removed but not the framing or plywood sheathing. The team secured 2” of polyisocyanurate rigid insulation to the sheathing. The 3-ply built-up roof—painted reflective white—was placed on top of this insulation. The aluminum sliding windows were replaced with argon-filled Milgard dual-pane windows, and the sliding glass doors were replaced with Milgard French doors containing SunCoat low-emissivity glass.
A Copperheart solar hot water heater was mounted on the roof and a Seisco tankless water heater was added to ensure hot water on demand. Also mounted on the roof was a wind-resistant, 1.6 kW PV system for converting sunlight to free electricity.
A Trane dual-compressor heat pump (19/17.6 SEER) was installed for heating and cooling. Ninety percent of the time, the smaller compressor, which uses 25% less energy is all that is needed; the larger compressor kicks in during extreme temperatures. All incandescent light fixtures were replaced with fluorescent light fixtures and lights. Carpet was replaced with ceramic tiles, which also have thermal mass properties.
Although Miller acknowledges personal motivations for remodeling the Hawthorne house, he sees a much bigger motivation: “These old homes are just sucking up energy. … I sincerely believe we should all be working to make the planet healthier. Fixing up our existing housing stock is one of the biggest places we can make a difference.”
- Tucson Electric Power five-year heating and cooling guarantee for a $1.26 average heating and cooling cost per day
- 1.6 kW BP solar photovoltaic system
- Copperheart solar hot water collector
- Seisco tankless water heater
- 2" rigid R-13 insulation on roof
- 1½” rigid polyisocyanuratewall insulation (R-9.7)
- Argon-filled Milgard dual-pane windows with 0.31 U-value and Suncoat low-e2 glass
- New Trane XL 19/17.6-SEER high-efficiency heat pump
- Programmable thermostat
- Ceiling fan with CFL lights
- Builder: John Wesley Miller Companies, Tucson
- Founded: 1956
- Featured project: Retrofit of one adobe home in historic Sam Hughes neighborhood
- Number of units: One home: three bedroom, two bath, one office
- Square footage: 1,990 square feet on 0.206 acres
- Rehab cost: $100,000
- Heating and cooling costs: 30% less than neighbors; 75% less than pre-retrofit
- Tucson Electric Power 5-year guaranteed heating and cooling bills ($1.26/day)
- Federal tax credit $2,000 per solar system
- State tax credit $1,000 per solar system
- Utility rebate $4,800 for PV; $1,300 for solar hot water
U.S. Department of Energy Residential Retrofit Resources
DOE seeks to offer comprehensive, whole-house technical information to the industry and consumers to encourage energy-efficient remodeling and retrofit practices in our nation's existing homes. Visit the Residential Buildings site
to access a variety of useful resources, including Home Performance with Energy Star program information, case studies of successful retrofits in all climate zones, energy code and tax incentive information, guidelines for air sealing, solar and photovoltaic systems, and
Photo: The remodeled home retained the historic landscaping with plants and ground cover that require minimum irrigation.