The Secrets of a Super-Green Home in Oregon, Revealed

By: Patrick Sisson

The exterior of the Karuna House is clad in FSC maple and plaster. All images via Hammer & Hand.

The Karuna House in Newberg, Oregon, may offer a stunning view of nearby vineyards, but the most idyllic aspect of this high-tech residence may be due to what’s hidden within its walls. The second home of Eric Lemelson, a local developer and environmental advocate, the building is so well-insulated, all of its energy needs, including charging Lemelson’s Tesla, are readily provided by a solar photovoltaic array of less than 10 kilowatts. While the home boasts plenty of advanced features, the designers, Holst Architects, probably should have also included an extra-large mantle, considering the unprecedented number of awards and certifications the project has earned: Passive House, MINERGIE, LEED Platinum, Department of Energy Zero Energy Ready Home and Earth Advantage Platinum.

According to Zachary Semke, Director of Business Development at Hammer & Hand, the company that built the home, the practices and products that went into constructing this green case study, which some have called the “world’s greenest home” for achieving so many different certifications, aren’t as complicated as one may think. The $2 million, three-year project demonstrates that high-minded and high-design aren’t mutually exclusive, or out of the reach of current technology. The L-shaped home, which covers 3,500-square-feet, has an estimated annual energy bill of just $50.

“It’s exciting because it applies physics to building construction in a smart way, and makes it practical and feasible to slash heating and cooling costs by 90 percent,” says Semke. “You’d be doing passive house a disservice by calling it an engineering feat. The whole point is that it’s not really that hard.”

The principles of passive house construction.

Building homes with super-efficient insulation isn’t anything new; contractors tried to do this in the ’70s, spurred on by the growing environmental movement as well as the energy crisis caused by the oil embargo. But without a sophisticated understanding of how air, hear and moisture work inside building assemblies, or the HVAC (heating, ventilating, and air conditioning) systems that have since been developed to circulate air, these early attempts at super-tight envelopes had significant condensation problems. Today’s computer modeling programs, such as WUFI Passive, can help formulate interiors with better airflow, allowing for a much more livable space.

The exterior of the Karuna House showcases just how far the modeling systems have come; the boxy, plaster-and-maple shape came first, as opposed to strictly focusing on performance. The rectilinear form, boasting large banks of windows, isn’t necessarily the easiest to insulate, but improved modeling and construction techniques make it possible to bring more design-forward homes up to the passive house standard. Karuna is 10 times more airtight than a standard, code-built home.

“You can make a passive house now that looks like anything on the cover of a high-design architecture magazine,” says Semke.

One of the key facets of Karuna’s increased performance comes from what’s under the floor. When building a passive house, the performance of all six sides of the cube matter; if the building isn’t “thermally isolated” from the ground, then the efforts to insulate the facade and roof are less meaningful, and require thicker walls.

The Karuna House uses a material called EPS geofoam— a type of polystyrene that basically functions like high-tech, dense Styrofoam—to separate it from the earth. A 12-inch thick section of foam, laid on top of gravel, forms an insulating layer between the foundation and the ground. Think of it like the packaging wrapping your latest appliance.

Not surprisingly, to achieve such an incredible seal on the home, the walls are layer cakes of materials and material technology. Airtight and watertight, each side contains lime plaster, studs built from FSC-certified wood, a layer of cellulose insulation (recycled newspaper), polyiso foam and a rain screen system made of cedar siding.

Doors and windows create gaps in these super-efficient walls—like holes in a bucket, according to Semke—but Hammer & Hand figured out ways to reduce the energy loss from every entrance. Every door, including a handmade one that leads to the downstairs wine cellar, boasts a series of gaskets and a multipoint lock system. Semke compared them to a bank vault. And the triple-glazed Optiwin windows lining the exterior achieve net-positive energy performance, based on the amount of sunlight that floods into the property. Motorized shades balance solar gain and help provide passive cooling.

When people hear passive house and airtight, they often think hermetically sealed. That’s not the case, according to Semke. In fact, despite the super-tight seal, passive homes often have better air quality, since air doesn’t leak in through gaps in the wall or the crawl space. Instead, a machine called a heat recovery ventilator (HRV) constantly circulates fresh air through the home. The system is set up to conserve power; streams of fresh air and exhaust get filtered through the system next to each other, with a system of baffles separating them, allowing for the transfer of 90 percent of the heat energy.

“People hear air-tight, and they freak out,” says Semke. “But with a system like this, you know exactly where your air is coming from.”

The HRV is just one part of the home’s mechanical system. An air-to-water heat pump also circulates energy throughout the home, and an on-demand hot water system “pre-heats,” picking up cues, such as someone entering the bathroom, to more efficiently distribute energy during the day.

“The point of this was to show that green design and architecture can be synonymous with good design,” he says. “People may think green building needs to be ugly, but that’s just not the case. It’s really a different experience being inside a building like this. The air is so fresh, and with Karuna, there’s such an amazing connection to the outside through the windows. You’re breathing in air as fresh as what’s outside.”

Courtesy: http://curbed.com/

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