Passive House: The Next Evolution in Green Design

small-entrywayBy Linda Seggelke

There is a method of construction relatively unknown in this country. Though it has been popular in northern Europe the last few decades, Passive house actually has its roots in the U.S.

The history of passive house starts with the oil embargo in the 1970s, which impelled some to look for ways to improve the efficiency of their homes. The University of IllinoisSmall Homes Council was one of first research teams that got involved with super insulation, one of the cornerstones of passive house. By the mid-80s, there were about 30,000 passive house projects finished in North America.

But then, the concept seemed to disappear, like a forgotten technology. There were several political and economic changes, the most important being the drop in energy prices. The concept then migrated to Europe where the cost of energy kept rising.

Passive house in the U.S. is starting to break out of its niche. The movement is strongest in the Pacific Northwest and New England, though it can be used in any climate zone. Passive House Institute US (PHIUS), which recently moved its headquarters to Chicago, has certified around 500 buildings in North America. These are all single-family homes, though multi-family is a perfect fit for passive house, as are commercial buildings where envelope optimization makes sense.

One of those is a single-family home in River Forest. Constructed in 2012, it was the first passive house in the region. The house was designed by architect Tom Bassett-Dilley and constructed by Brandon Weiss of Weiss Building & Development and Eric Barton of Biltmore Insulated Concrete. They, along with Katrin Klingenberg, co-founder of PHIUS, spoke about the concept at this year’s Building Green Chicago Conference.

One of the challenges with passive house is convincing a building industry resistant to change. “There’s been more than one time … that I’ve told someone they’ve been doing it wrong their entire life,” said Barton. “You find contractors that simply don’t want to do it any other way because they are comfortable with how they’ve done it. But that’s not where innovation comes from.”

The economics of passive house require different thinking as well. For most projects in climates similar to Europe, these structures see a five to ten year payback. The important thing is to think of the cost savings with a house that is this thermally efficient. A slightly higher mortgage is easier to handle when the gas and electric bills are fractions of what they would have been.

Many municipalities that offer subsidies or other benefits for building green have started to incorporate passive house into their benefits. Massachusetts was the first state to do so, and there are now similar ordinances in Oregon and San Francisco.

In the end, however, a passive house is one of the most sustainable structures you can build. With renewables, according to Klingenberg, a building held to passive house standards is meeting the 2030 Challenge today.

“It’s important to have sustainability in our consciousness, because there is no alternative to sustainability,” said Bassett-Dilley. “Well, there is, but it’s really ugly and it doesn’t involve us anymore. We have to get serious about what sustainability means.”

small-silltapeWhat makes passive house different from other construction methods? It starts with the outside. “Essentially, you are designing your shell so well that you can heat your house with a hair dryer,” said Klingenberg. “A thousand Watts, if you do it correctly, is enough to heat a single-family home.”

As in a traditionally built, timber-frame house, the building loses heat at a high rate without proper insulation, leading to a higher demand on the furnace in order for occupants to feel comfortable. A passive house envelope is by design so well insulated, that there is virtually no heat loss, and no thermal bridging. This results in a superior level of comfort. Some home-buyers aren’t as excited about energy savings but really like the idea of a comfortable home with a stable indoor temperature year-round.

After the construction of an airtight, well-insulated and continuous envelope, a passive house calls for high performing windows, an efficient heat recovery ventilator and smart placement of trees to control shading.

PHIUS has also developed a versatile piece of building energy modeling software. The dynamic interface allows a user to tweak their design, from window placement and building compactness, to maximize a structure’s efficiency.

Weiss, who spent some time traveling around Europe playing professional basketball, first encountered passive houses in Germany years ago, though he didn’t know at the time what they were. He just knew they were high quality. “You can’t build passive house without a super well-crafted home,” he said.

Passive houses are also great at handling moisture in every form it can exist in a home. Roughly 95% of homes fail because of moisture; this building design reduces that risk. This leads to buildings lasting for centuries as they do in Europe, as opposed to decades like in the U.S.

Indoor air quality is another important component. Because a passive house is airtight, the ventilation unit is the only source of airflow. There are no external pressures in the home, no way for dust and debris to move around and settle. On the River Forest project, Weiss explained how the homeowners adjusted to this aspect of their new home. “The client was dusting her old house quite a bit,” he said. But after nine months living there, “she had dusted her house once and that was because she had company coming over.”

Years ago, there were few vendors of passive house-rated windows in the U.S market but there are now dozens. Nevertheless, part of the challenge in building to this standard is finding components for buildings that are up to proper grade. Generally, however, the technology isn’t that extreme; it really is just about installing a lot of insulation, using air sealing tape and paying attention to shading.

PHIUS spends a lot of energy certifying passive houses, and holds the buildings to high criteria. One challenge is creating a standard that works around the world, in any climate zone. “The Pacific Northwest and the East Coast have had a really good following and passive house has really grown there,” said Weiss. “But it even makes more sense from an economic perspective because of the harsher climate here.”

Bassett-Dilley used to work for the Oak Park Historic Preservation Commission. Looking at the old Georgian, Prairie Style, Colonial and other homes that the suburb is known for, what he started to see in all of them was a uniformity of compactness. Without a huge mechanical system, traditional builders had to be mindful of the shape of a building and of how many windows and their placement, or else their clients suffered. “That was an ‘ah-ha’ moment for me,” he said. “There are some timeless things going on here with these buildings that we can use today.”

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