Chie Kawahara and husband Kurt Hurley turned their almost-century-old bungalow into Santa Cruz's first Passive House.
The secret to completing a 13-month green remodel that transforms a 91-year-old California bungalow into a model of energy efficiency: Mrs. Hurley’s cookies.
The cookies, a modified Mrs. Fields chocolate chip recipe with added orange zest and oatmeal left whole, were a hit with the builders, says Chie Kawahara, who with husband Kurt Hurley owns the Van Ness Avenue home—Santa Cruz’s first Passive House.
“They’ve been my key ingredient to ensure project success, whether it be construction, business system implementation or nonprofit governance,” she says.
Today, a plate piled high with said cookies sits on the Amish-made brown maple dining table. Natural light streams through the large, triple-glaze windows. The home is well lit and airy—a ventilation system supplies constant fresh air—and the temperature remains constant and comfortable.
It feels and looks like a luxury bed-and-breakfast, complete with a Japanese soaking tub on the back deck—but minus the pricey heat and energy bills. Passive Houses require so little energy that conventional heating and cooling systems aren’t needed.
Hurley and Kawahara, along with Santa Cruz Green Builders, remodeled the home to meet the rigorous efficiency standards through an extremely insulated roof, floor slab and exterior walls, as well as special windows and tight sealing. This helps the house maintain a comfortable, constant temperature, even when it’s extremely hot or cold outside.
Passive Houses use 90 percent less energy than typical existing homes and 75 percent less energy than most new homes, according to the Passive House Institute, which sets the PH Standard. They rely on the sun, internal heat sources (such as shower steam) and heat recovery, making active heating systems unnecessary, even on the coldest winter nights. Strategic shading, window glazing and ventilation keep Passive Houses cool on warmer days without air conditioning.
Kawahara, a retired IT manager, and Hurley, a clean-tech investor, call it the Midori Haus. “Midori” means green in Japanese, which she speaks; “Haus” is because he speaks German.
Hurley and Kawahara, who are active members of Passive House California (PHCA), bought the house in August 2010, and moved in this March. In addition to achieving Passive House certification, the home received 288 points with the City of Santa Cruz Green Building Program and a California Advanced Homes Program (CAHP) rebate, an incentive program intended to encourage energy efficiency and sustainable development.
The couple is also participating in the Thousand Home Challenge, a program that aims to reduce the total annual energy consumption of existing North American homes by 70 percent to 90 percent. Participants have to show energy consumption for a year, and achieve reductions through a combination of energy efficiency, renewable resources and behavioral choices.
In addition to being resource-efficient, sustainable homes can and should be comfortable, too, Hurley and Kawahara say.
“We’re not stoic people as Americans,” Hurley says. “We live large. How can we take ownership of these issues and live comfortably and wisely? We tried to take the best of what’s out there and show what’s possible. Comfort that’s wise. Well-spent luxury. What better thing to be passionate about?”
The 1,569-square-foot house has three bedrooms and two bathrooms. In addition to its energy- and water-efficient appliances, the house includes LED lights, a solar thermal system and a paperstone kitchen countertop made from FSC-certified, post-consumer paper product held together with petroleum-free resin. The couple hang-dries laundry in the house instead of using a clothes dryer, and they installed a Murphy bed in the office rather than constructing an additional guest room, thus reducing the home’s footprint. Builders re-used existing materials whenever possible, including interior doors, fir floors, baseboards and trims, and even salvaged the original 1922 built-in buffet, keeping the piece covered during construction before refinishing it.
Future plans include a rainwater catchment system that supplies water to flush toilets, and a solar photovoltaic system to generate electricity.
A heat-recovery ventilator (HRV) in the house moves exhaust air out and brings fresh air in, using the heat in the outgoing household air to warm up the fresh air. Plus the unit’s filters keep dust and pollen from entering the house. So in addition to being extremely efficient—HRVs can recover up to 85 percent of the heat in the outgoing air—the system provides excellent air quality without drafts.
This passive heating and cooling is also more comfortable and affordable. The couple says their average PG&E bill over the last five months is $55. The tightly sealed building envelope keeps heat loss at a minimum. On a cold March morning, for example, where the outside temperature measured 43 degrees Fahrenheit, the temperature in the house varied only 2.5 degrees from the design temperature of 68 F.
“We are saving lots of energy without having to throw on lots of sweaters,” Kawahara says.
The Passive House concept originated in Germany in the 1990s. Since then, the movement has taken off in Europe—of the 40,000 to 50,000 passive houses worldwide, about half are in Germany, although not all of these are certified—and is gradually growing in the U.S.
According to Bronwyn Barry, founding member of PHCA, there are about 40 Passive Houses in California, both certified and non-certified but designed and built using the Passive House Planning Package (PHPP), a design tool that calculates a building’s heating, cooling and primary energy demand based on climate zones and other data.
Barry says she’s seeing more homeowners and builders build to the Passive House Standard: homeowners appreciate the advanced comfort and indoor air quality, while builders and architects want to achieve the performance benchmarks associated with the standard, she says.
“If we’re going to take carbon reduction seriously, this is the cheapest, most effective way to ensure that we're building some great structures for the next generation,” Barry adds. “Plus, in California, with our mild climate, building a Passive House is so easy compared to most other places in the U.S. It requires a small amount of additional insulation and some real attention to the details—something we expect from every other consumer item we purchase except our buildings.”
Santa Cruz Green Builders co-owner Taylor Darling says interest in Passive Houses is growing rapidly.
“There are a lot of benefits to it: energy-efficiency, indoor air quality and a much more comfortable home,” he says. “Those things alone will drive growth, but as energy prices continue to go up, it’s going to make more and more sense financially to build to Passive House standards as well.”
The Midori Haus was Santa Cruz Green Builders’ first certified Passive House. But all of its construction projects—including the Penny Ice Creamery and the Picnic Basket—reflect the 5-year-old company’s commitment to using sustainable materials and building efficient structures. Darling and co-founder Spencer Keenan are both certified green builders through Build It Green, a nonprofit green building program in California.
“The Midori Haus is a really great example of what can be done,” Darling says. “If you don’t have the money to go all out and do everything they did, that’s OK. Take some examples from that house and use them—there’s a lot of takeaway.”
Barry calls it “hacking down the dense brush for anyone to follow safely behind.”
As most of the existing building stock is in need of upgrades, Hurley and Kawahara have shown how retrofitting a home presents an opportunity to build to a level of efficiency “that means something,” she says. “By demonstrating that Passive House is possible, this home has seized the opportunity to make significant comfort and performance improvements and will likely not require any additional retrofitting for the next 100 years.”
The idea of taking an old house and applying forward-looking efficiency technologies and building practices while maintaining the home’s soul was crucial to Hurley and Kawahara throughout the remodel process. They’re hoping it resonates with other homeowners, too, and they’re eager to share their green-building lessons learned. They open their home to tours and sit on panel discussions about Passive Houses. Says Hurley, “Looking to the past and the future—that’s a unique and beautiful thing.”