TechPractices: Environmental Showcase Home, Phoenix, AZ

PATH's Technologies in Practice are large scale housing projects throughout the U.S. where innovative technologies are being installed and used. Information is presented from the viewpoint of builders and remodelers who can use these examples as models for projects of their own.

Summary

If you had enough time and budget to build the leanest, greenest, and cleanest home in the country, what would it be? An architect got that opportunity paid for by his local utility. The intent of the Environmental Showcase Home (ESH) is to demonstrate that products available on the market can make a resource-conserving home without compromising comfort or aesthetics.

Details

This 2,640 sf single-family home was planned from the start to incorporate lots of state-of-the-art sustainable design strategies and materials. A "shopping center of ideas," the house contains over 150 technologies and special material uses. Although products were selected for recycled material, low embodied energy, ozone protection, indoor air quality, and durability, a comprehensive discussion would fill a book (and it has). Here we'll focus on energy and water use in this hot, arid climate.

The program's main goal is reducing the large potential cooling load of a house in Phoenix, blending passive and active systems to slash energy use. Although advanced systems are used for maximum energy performance, substantial energy savings are achieved before needing to resort to high technology. For example, the house is oriented lengthwise on an east-west axis to expose less area to the hot morning and afternoon sun. R-24 block wall, R-22 wood wall, R-38 roof, and R-11 doors slow heat conduction through the envelope. Using a high-thermal mass strategy to regulate daily heat absorption would not work in this climate with its hot summer nights. Designers opted for a medium-thermal mass approach, using 8" foam-insulated concrete "Integra Block" walls that feature reduced webbing to allow more insulation and less thermal bridging. Drywall clips were used in the partitions and stud walls, eliminating lots of wood blocking to make room for more insulation.

Careful design and specification of windows is a cost-effective way to save energy. The developer claims that reducing the window area by 10%, and specifying glazing with a slight grey tint and low emissivity (low-e), actually reduces total home energy use by 10%. Further savings are achieved by shading techniques and north-facing clerestory windows that admit natural light without direct solar gain.

The whiz-bang stuff is here too. HVAC "smart" zoning controls allow one HVAC unit to provide four independent temperature zones for space conditioning. All ducts are installed within the conditioned envelope, eliminating wasteful conductive heat gain from unconditioned spaces, like attics. A variable speed heat pump, with a seasonal energy efficiency rating (SEER) of 14, concentrates the air conditioning exhaust heat to provide hot water. There is also a solar water heater. Phoenix's sunny climate lends itself to various solar strategies. Heliocol's pool heating system costs no more than conventional systems, yet relies purely on the sun. Providing half the home's electricity during peak summer demand, the low-voltage direct current (DC) generated by the Solarex rooftop photovoltaic panels is converted to alternating current (AC) for household power.

Among the appliances is a high-efficiency dishwasher using 70% less energy and 40% less water than typical models, and a high-efficiency refrigerator using 30% less energy (refrigerators are a major energy consumer). General Electric's "Profile" cooktop, which never gets hot, uses an induction coil with instant heat response, using 10% less energy than comparable models. Daylighting from the north-facing clerestory windows reduces the amount of illumination needed. With task lighting instead of general lighting, and fluorescent lamps instead of incandescents, the home uses 50% less electricity for lighting than a comparable home.

Builders can expect buyers to demand more water conservation in homes. Phoenix's population is expected to double in the next few decades, and the water table has dropped 120 feet in the last 35 years. The ESH cuts water use in half mostly by using rainwater harvesting to supply the site landscaping and vegetable gardens. This is supplemented by greywater use, filtering the water from sinks, tubs, showers, and the washing machine for landscape irrigation. Geoflow's sub-surface irrigation eliminates water loss from evaporation. Low-flow faucet aerators increase water volume by mixing it with air, saving additional water. A low-flow showerhead by Resources Conservation features an on/off switch allowing users to shut off water supply without changing valve positions.

Careful design and specification of windows is a cost-effective way to save energy. The developer claims that reducing the window area by 10%, and specifying glazing with a slight grey tint and low emissivity (low-e), actually reduces total home energy use by 10%. Further savings are achieved by shading techniques and north-facing clerestory windows that admit natural light without direct solar gain.

The whiz-bang stuff is here too. HVAC "smart" zoning controls allow one HVAC unit to provide four independent temperature zones for space conditioning. All ducts are installed within the conditioned envelope, eliminating wasteful conductive heat gain from unconditioned spaces, like attics. A variable speed heat pump, with a seasonal energy efficiency rating (SEER) of 14, concentrates the air conditioning exhaust heat to provide hot water. There is also a solar water heater. Phoenix's sunny climate lends itself to various solar strategies. Heliocol's pool heating system costs no more than conventional systems, yet relies purely on the sun. Providing half the home's electricity during peak summer demand, the low-voltage direct current (DC) generated by the Solarex rooftop photovoltaic panels is converted to alternating current (AC) for household power.

Among the appliances is a high-efficiency dishwasher using 70% less energy and 40% less water than typical models, and a high-efficiency refrigerator using 30% less energy (refrigerators are a major energy consumer). General Electric's "Profile" cooktop, which never gets hot, uses an induction coil with instant heat response, using 10% less energy than comparable models. Daylighting from the north-facing clerestory windows reduces the amount of illumination needed. With task lighting instead of general lighting, and fluorescent lamps instead of incandescents, the home uses 50% less electricity for lighting than a comparable home.

Builders can expect buyers to demand more water conservation in homes. Phoenix's population is expected to double in the next few decades, and the water table has dropped 120 feet in the last 35 years. The ESH cuts water use in half mostly by using rainwater harvesting to supply the site landscaping and vegetable gardens. This is supplemented by greywater use, filtering the water from sinks, tubs, showers, and the washing machine for landscape irrigation. Geoflow's sub-surface irrigation eliminates water loss from evaporation. Low-flow faucet aerators increase water volume by mixing it with air, saving additional water. A low-flow showerhead by Resources Conservation features an on/off switch allowing users to shut off water supply without changing valve positions.

Installation/Construction

Construction took seven months, with site preparation beginning two months prior. Engineered wood and a lightweight metal roof required less structural support, saved materials, and potentially saved costs. Construction-site recycling bins were used to reduce the amount of landfill and therefore reduce disposal fees.

The designers created a horizontal, overhead volume with two functions. In addition to serving as an attractive light shelf for the clerestory windows, the volume houses the air distribution, efficiently keeping it within the conditioned envelope.The ductwork is installed with direct runs and few bends, reducing impedances to air flow. By connecting the ducts with fiberglass tape and sealing the connections with mastic, tight air distribution is achieved with little air loss.

Benefits/Costs

By using medium thermal massing with high insulation, energy consumption is shifted to nighttime and early morning in the summer and daytime in the winter, when demand for electricity is less and rates are lower. The developer claims that the home requires 60% less energy than a typical energy-efficient home. When photovoltaics are considered, energy reductions can increase up to 80%, saving approximately $1,100 per year in energy bills. However, even in the sun-soaked Arizona desert, the installed cost of some solar technologies is not considered cost-effective. But the cost of solar cells is steadily decreasing.

The house demonstrates that 55% water savings can be achieved in this climate with the techniques used. The water-saving appliances also conserve energy because less water needs to be heated.

Code/Regulatory

Arizona Public Service (APS), the local electric utility, introduced a Good Cents Program to help builders meet federal energy standards. APS teamed up with the Arizona Department of Environmental Quality and Region IX of the Environmental Protection Agency to initiate the Arizona Strategic Alliance (ASA). In this sprawling sunbelt region, The ESH is a dramatic statement by ASA to promote energy efficiency; if current energy use trends continue, an additional power plant will be needed.

Feedback

At the time of construction, interest in environmentally-friendly, energy-efficient homes in Phoenix was not great. Although many of the area's residents considered themselves "environmentalists" or "conservationists," many did not connect these issues with housing design and construction practices. That is now changing, as large builders are using more environmentally-friendly construction practices. Some local utilities administer production builder programs to encourage the construction of energy-saving homes. In this sense, the energy seller itself is taking the initiative to decrease the need for its services, to avoid additional capital-intensive power plants.

APS held public participation meetings in the neighborhood, and planned tours and open houses for consumers, builders, and trade people, with materials and systems displayed in the garage. Cutouts in the walls and ceilings allow systems to be seen. A book is available for the public to understand the innovations in the home. Based on the home's reduced energy demand, power plant-generated pollution is calculated to be 4,881 lbs of air emissions per year for this house, compared to 25,544 lbs per year for the conventional energy-inefficient home. The ESH has received at least 24 regional and national awards.

As a pioneering practice, there were several problems with the construction-site recycling bin program. The process for pickup and delivery of the bins was cumbersome, and they took a large amount of space. Still, a larger amount of waste went to the landfill than expected. Some of this can be attributed to the packaging used for a large number of products. As a showcase home, several systems were used for a single function, such as three different sources of domestic water heating. Since then, construction site recycling bins are used by large builders such as Del Webb.

Contact(s)

Do you have a specific question? Try the contacts listed below:

Environmental Showcase Home
Arizona Public Service
P.O. Box 53999, Sta. 8666
Phoenix, AZ 85072-3999
602-250-2100
http://www.aps.com/general_info/newsrelease/newsreleases/NewsRelease_51.html

Jones Studio, Inc.
4450 North 12th St.
Phoenix, AZ 85014

Environmental Protection Agency Region IX
602-371-7171

Heliocol Arizona, Inc.
939 S. 48th St., #207
Tempe, AZ 85281
602-829-0083

BP Solar
630 Solarex Court
Frederick, MD 21703
301-698-4200
http://www.bp.com/

General Electric Co.
9500 Williamsburg Plaza
Louisville, KY 40222
800-626-2000
http://www.geappliances.com/

Geoflow, Inc.
200 Gate 5 Rd., #103
Sausalito, CA 949766
800-828-3388
http://www.geoflow.com

Resources Conservation, Inc.
Greenwich, CT 06836
800-243-2862