The largest net-zero ready housing development in the United States is tapping into the sun two ways: using solar power to create thermal and electrical energy for the 7,500 homes and apartments under construction in Austin, Texas.
A geothermal system of cross-linked polyethylene (PEX) pipe loops underneath the $2 billion development to reduce energy consumption for heating and cooling by up to 65 percent compared with traditional heating methods.
The plans call for the community of Whisper Valley to be able to meet the carbon-neutral standards adopted for Austin's municipal building code. The city's goal is to reduce carbon emissions to zero by 2050.
The first 237 houses built in Whisper Valley are equipped with a double U-bend PEX pipe and a heat pump that take advantage of the fairly constant ground temperature to create renewable energy for heating and cooling. So far, 313,000 lineal feet of Rehau Raugeo-brand pipe called PEXa has been used.
Based in Leesburg, Va., Rehau has been manufacturing its PEX pipe with a high-pressure peroxide method of cross-linking that it pioneered in 1968. The company says the method gives its pipe better flexibility, strength, and chemical and corrosion resistance.
With $178 million in sales, Rehau is the No. 30 pipe, profile and tubing extruder in North America based on Plastics News' latest ranking.
In Whisper Valley, all builders are required to hook up to a 5-mile loop of underground distribution piping that links the homes to a geo-exchange network. The system uses the earth's relatively steady temperature range of 45° - 75° F in Austin to heat and cool structures.
At all lots, boreholes are drilled to depths of 335 feet and the Rehau pipe loops are inserted. Each PEX vertical pipe loop connects to a system of horizontal pipes. In the winter, a fluid with antifreeze and water circulates through the ground loop system. It absorbs stored heat that originated from the sun and carries it indoors.