Test houses across the country are helping architects and builders improve efficiency and health where we live. The latest version is part of a long-term partnership between Whirlpool and Purdue University. Dubbed ReNEWW—Retrofitted Net-Zero Energy, Water, and Waste—the house serves as a lab where graduate engineering students plus occasional Whirlpool engineers will live while conducting research.
The ReNEWW House is the answer to having a ready-made lab for student projects. Eric Bowler, senior engineer in Whirlpool’s sustainability group, says the house solves the dilemma of participants in the Whirlpool Engineering Rotation Leadership Development program at Purdue not having enough time to complete independent studies because they lacked the necessary equipment.
The 1928 bungalow has been rebuilt to achieve net-zero energy with a low carbon footprint. Bowler says fresh thinking is needed in this area because efficiency progress in home appliances has dwindled in the past decade. “If I were to show you a curve of appliance energy use by year from 1970s to today it would look like hockey stick—it dropped dramatically in ’80s to ’90s and then leveled off.”
Thinking Outside the Ice Box
ReNEWW House should help get that efficiency curve climbing again as the basement is set up as a lab to accomplish just that. “The mode I had in mind when I pitched this project was that kind of garage innovation theology like Steve Jobs,” Bowler says. “A university gives you a sense of freedom to think outside the box, and if we want to make dramatic progress in appliance efficiency then we have to think differently.”
One example of different thinking is a refrigerator and dishwasher coupling. The pair shares a water-based heat exchanger that collects heat from the fridge’s condenser and uses it to warm water for the dishwasher. Not only does this make the appliances more efficient, but it also keeps the kitchen cooler.
Two floors above the basement lab are bedrooms for the researchers; the first-floor public spaces are open for tours. ReNEWW is intended to teach industry pros and educators about current and future best practices for sustainable residential design and building.
Geothermal, Solar, and Spray Foam
Before the retrofit took place, engineers monitored the house for a year to provide comparisons for energy, water, and waste savings. The initial HERS result was 177 and a blower door test revealed that the fully closed up structure experienced 12 complete air changes every hour. To Bowler, who works on designing things for maximum efficiency, those results highlighted where they needed to begin. “A solid building envelope is the base of any energy-efficient home,” Bowler says. “I think of it like a refrigerator—you’re trying to maintain interior space at a temp that’s different than the outside, which is similar to what homes do.”
Much of the original building’s foundation and framing was saved. Spray foam insulates the walls, foundation, and attic, however, the version used is less controversial than others thanks to a new blowing agent with a global warming potential (GWP) of 1, compared with most agents with GWPs in the 100s. Triple-pane windows and insulated siding complete the tight envelope.
Renewable energy is needed to achieve net-zero, but few houses employ geothermal along with solar power to make an electric meter spin backward. Three geothermal wells provide energy for a hybrid HVAC system. “We kept some basement and first floor ducts and installed a big heat exchanger driven by the geothermal heat pump,” Bowler explains. “Levels are zoned separately, so we can turn off the basement if no one’s using it and for the third floor, we did mini split systems also powered by geothermal.”
Like many products used in the house, the solar power isn’t your typical setup. “We used a start-up company’s product that combines electric and thermal,” Bowler says. Solar cells on front generate electricity and tubes underneath contain fluid that collects thermal energy to heat domestic hot water. Also, the flow can be reversed to melt snow off the panels and allow for solar production in winter.
A separate solar array connected to batteries powers lights and equipment in the lab. Even during power outages, research can continue. These PV-powered batteries are an experiment themselves. Most solar energy is generated in DC form then converted to AC to work with electric grids and then converted back into DC for plug-n-play devices. “This system stores the DC power directly,“ Bowler says, “so there’s no loss with conversion.”