Passive House Design Builds Efficiency into the Future

A Passive House retrofit offers energy-slashing solutions

20130321_092930_lower-resIt was a common situation: In 2009, a growing family decided to add on to their home to create more space. The solution, however, was not so common.

Sylvia Wallis, an associate architect with Los Angeles-based Harvey Davis Deveraux architecture firm, had designed a concept for a modernist, energy-efficient addition to the 100-year-old house in northeast Los Angeles-—but then she discovered the energy-maximizing principles of Passive House design.

Passive House design addresses what are generally understood to be best practices for building performance—adequate insulation, draft elimination, good glazing, effective ventilation and control of solar gains—to dramatically reduce energy consumption by up to 90 percent. The “efficiency first” approach emphasizes design and passive measures in the actual building shell, such as insulation and shading, over complex and expensive mechanical equipment and renewable energy systems, such as photovoltaics and solar thermal hot water systems.

Alert •• See related story: What’s Wrong with LEEDs

Envisioning the benefits for her clients’ house, now known as the Shift House, Wallis earned certification as a Passive House consultant and applied her new training. Her revised design, which integrates a hillside on the property and manages to avoid blocking views from the existing house, doubles the square footage of the home but also drops total energy consumption to less than half, via a heat recoveryhillsdale2012b-6 copy ventilation system and German-made airtight windows. In addition to the Passive House design elements, other sustainable features in the overall design include water conservation, rainwater harvesting, non-toxic materials, certified sustainably harvested wood, and energy efficient lighting, heating and cooling.

Adding to the challenge in this particular case, budget limitations have turned the house into an exercise in achieving Passive House standard using cost-effective solutions. It is calculated to meet standards for the existing house and addition, considered both individually and together, but costs are still being tallied.

California Dreamin’

Passive House building technique was explored in the United States in the 1970s, but it was a German physicist who further tweaked the concept and founded the international Passive House Institute, leading to the rapid implementation of Passive House construction all over Europe—almost 30,000 buildings have been built or remodeled in accordance with the stringent design principle. Lagging significantly behind, the U.S. can claim barely 100 Passive House-certified buildings. Of these, architect Bronwyn Barry, a member of the San Francisco chapter of the California Passive House community, estimates that our state currently boasts about 40 such projects, “all various degrees of inspired, calculated and certified.” Passive House retrofits are slowly gaining traction, although they are mostly extensive and intensive projects to undertake, making them more appropriate for major remodels.

Graham Irwin of Essential Habitat, a Northern Calif.-based consulting and design firm, one of the first certified Passive House Consultants in the country, has plenty of firsthand knowledge on the subject, including his design of the first Passive House retrofit in the country—Midori Haus in Santa Cruz, completed summer 2013.

“Passive House is the most cost-effective approach to high performance currently available,” says Irwin. “Not only is efficiency the cheapest ‘form’ of renewable energy, these passive measures function continuously for the life of the building. It’s a bit like relying on gravity for drainage rather than pumps—gravity never malfunctions.”

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Pros and ProsIMG_8978

So what advantage does the super insulation and air-tightness of Passive House offer? Luke Morton, a certified Passive House consultant in San Diego, explains some of the financial benefit: “Instead of buying a forced air system—$30,000 for furnace, thermostats, ducts and so on—your heating load (amount of heat required to maintain a temperature) for the coldest day is [equivalent to] a couple of hairdryers, around $100, and on the hottest day is really just some window shades to act as a solar heat shield. All we’re trying to do is give the house a winter jacket of insulation (of sorts) so that in the coldest days of winter, it can stay warm.

“This is something like what polar bears do in the Artic,” he continues. “They are warm-blooded, so they keep themselves warm by having a nice winter jacket of fur and fat, and then the little bit of heat loss that they still have due to the cold Artic weather is made up by their own internal metabolism. Building scientists know how to do this for houses. We design houses for the average coldest temperature, not the worst cold temperature. But since those do happen, even just 1 percent of the time, it’s nice to have a little backup in the form of a hairdryer (or heat lamp, electric blanket or maybe just a big television). And that’s a huge step forward in quality as a standard of practice for designers and builders in any location.”

Significant savings in upkeep and dollars is a deal-sealer for some people, but what really makes the case for Passive House buildings is personally experiencing the unique indoor environment that is easy on both senses and body mechanics. A steady, comfortable temperature is immediately noticeable, as well as a total lack of noise from the outdoors or any indoor mechanical systems; and although Passive House requires air tightness, a balanced mechanical ventilation system provides constant fresh air and superb indoor air quality—important for general health, and critical for some health conditions.

One caveat in wildfire-prone areas: Wallis cautions that particulates and other contaminants can damage the typical air filtration systems and would require additional types of filters that “will also increase static pressure in the system, decreasing energy efficiency. Further development of components is needed to address this problem, balancing needs for air filtration and energy efficiency, perhaps with a variable filtration system,” she notes.

Is this why Passive House design has taken off in central California, but is catching on less quickly in Southern California? Irwin thinksHillsdale1-overall otherwise, speculating that reasons include both lack of awareness and the misconception that the state’s climate is so mild that building performance doesn’t matter.

“In my experience, it takes early adopters to prove the concept of Passive House in a locality. After there are some nearby built examples, people discover the superior comfort, indoor environmental quality and sustainability, and realize that Passive House provides benefits in any location where you can’t be comfortable living outdoors all the time,” Irwin explains.

Wallis also notes that SoCal’s milder climate makes for lower and slower payback from heating and cooling savings; however, with component prices dropping as technology evolves, both are likely to accelerate.

In addition, a shortage of two elements—components, such as appropriate small HVAC systems; and local contractors familiar with Passive House codes and skills, such as air sealing—also add time and cost to a project. Finally, SoCal’s strong tradition of indoor-outdoor transparency has led to a preconception of Passive House air-tightness as an unwelcome feature.

The last is easily remedied, assures Wallis. “If done correctly, a Passive House project can maintain indoor-outdoor openness and transparency. And in any case, our building codes are heading closer to the Passive House criteria with each revision.” Unlike San Diego and San Francisco, L.A. doesn’t have its own chapter of the California Passive House organization, but Wallis plans to lead tours and host film events here, to familiarize prospective builders and upgraders with the technology.

“There is a lot of low-hanging fruit available for improving existing SoCal housing stock,” Wallis notes. “Much of it was built on the assumptions of temperate climate and cheap energy. A small investment in air sealing, insulation and balanced heat recovery ventilation will yield big reductions in our regional heating and cooling energy needs.”

Architects and remodelers, take note.

*If you’re interested in sustainable building you might also enjoy….”

~ Radical Architecture for a Sustainable Future

~ What’s Wrong with LEEDs

~ Grey Water, Green Plants

~ Biodome Gardens Laugh at the Weather

Photo of Midori Haus courtesy Kurt Hurley

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