Jul 13, 2018
Kathryn and Chris Johnson started talking about their dream home even before they got married. Kathryn’s parents both grew up on farms, instilling in her a kind of “back to the land” sensibility. Chris remembers drawing houses with his brother for summertime entertainment in the cool basement when it was hot outside and was influenced by the energy crisis of the 1970s.
But perhaps the biggest impact on their journey toward building their Net Zero Energy Passive House was their time visiting and living in Germany over the past 25 years, where Passive House principles are more prevalent. “We learned how Germans built homes, and a lot of the ideas struck us as much more practical and comfortable than the most common American methods."
So when the opportunity came along to build, they knew they wanted to pursue the Passive House certification. When they started the building process, they gave a name to their new home and set up a blog: SweetTreePassiveHouse (they tap the maple trees on their property to make maple syrup; they also have a crab apple tree, peach tree, and apple tree, hence the name). The beauty of this blog is its authenticity—these are two people that set their sights on building a more practical, comfortable, and beautiful home, which will happen to not have any energy bills.
Rise caught up with them just days before their move-in to a brand new, soon-to-be-certified Passive House, located in a western suburb of Minneapolis. The custom-design of the home did make it more expensive. But oh, it is worth it! Why? It’s so hard to choose, but here are the five coolest features of their home.
This is essential for our society’s transformation to a clean energy economy, commonly called electrification. That means no gas heater, no gas stove, no gas fireplace. How? The technology exists: induction stoves are leaps and bounds better than the old electric stoves that were hard to clean and hard to control the heat level. Electric heat pumps to cool and heat the house have become much more efficient. Hot water is heated with an AO Smith air-to-water heat pump. The benefit of no natural gas is threefold:
The central tenet of a passive house is its windows’ orientation toward the sun in order to take advantage of the sun’s free heat in the winter while having shading on that side in the summer to keep it cool. The home needs to keep that heat inside, which means the walls, windows and doors have to be super well insulated—and where they come together must be tightly sealed so there are no air leaks. The Johnson’s home accomplishes this through insulated concrete forms (ICF)—8 inches of concrete plus foam insulation + stucco = 24-inch walls. They chose German-made Muller Schreinerei triple-pane windows—aluminum on the outside and wood on the inside—rated for Passive Haus, with an astonishingly low U factor (which measures a window’s resistance to heat flow). Opening and closing the windows and doors is like opening and closing a safe. It is so airtight that their blower door test came back with 0.35 air changes per hour (ACH) at 50 Pascals pressure. For context, building code in Minnesota was recently lowered from 5 ACH to 3 ACH (at 50 Pascals); LEED Homes v4 will give you two points for a blower door test that comes back at 2.0 ACH or less. Now that is a tight building envelope!
We all like to be comfortable, and our thinking evolves as we discover new materials or technologies that we would like (and never knew we wanted!). In-floor heat, for example, is a game-changer for homes located in cold climates—so that was initially Chris and Kathryn’s hope. But once they came across the concept of a Passive House, they realized that you could build a home so well insulated that you did not need in-floor heating: the floors never get cold! “That’s the solution to the comfortable house,” Chris says. The additional benefit of a well-insulated home is how quiet and draft-free it is. Won’t the indoor air get stuffy and stinky? No, the tightness of the home is balanced with a very low-speed Energy Recovery Ventilator (ERV), along with a Zehnder ComfoFond-L Eco 550—a geothermal heat exchanger used to pre-heat or pre-cool outdoor air before it reaches the ERV—to efficiently bring in fresh air 24/7.4.
One of the first things you notice about the home is its beauty—filled with natural sunlight, exposed concrete walls, wood floors and trim. The wood was obtained from various local sources: an old elm tree from their previous yard; maple stair treads from their son’s godfather who collected and sold local hardwoods to artists. Some materials, including Corian pieces, lights, and doorbell chimes, were sourced from online neighborhood postings–which also helped the Johnsons reduce their upfront cost. Among all the natural materials are primary color accents on each floor, showing up as a red stripe in the Corian countertops, or through the blue, red, or yellow Marmoleum flooring in the kitchen and bathrooms. While the main roof of the house has a south-facing 45-degree angle (ideal for solar panels), the flat roof of the garage is green (meaning full of plants)—further insulating the garage and providing a gorgeous view of a garden from the second floor of the home.
Passive Homes are meant to utilize 80%-90% less energy than their conventionally built counterparts, so you’d expect Johnson’s energy bills to be very low. They will use electricity for cooking, some heating and air conditioning, ventilating, washing, and other appliances and electronics—and that electricity has to come from somewhere. In keeping with locally produced materials, Chris and Kathryn are producing their own electricity as well, with a 9.1-kilowatt system of solar photovoltaic panels on their roof. What size system should produce enough electricity to more than cover their consumption? With Xcel Energy’s net metering program, Xcel Energy will be paying the Johnsons for any extra electricity they produce over and above what they consume over time. And because of their solar-charged battery for back-up power, Kathryn notes, “Even if the power went out for two weeks, we wouldn’t have to worry about the pipes freezing.”
Those are some of the coolest things about the house. But truly the best thing about this project is the homeowners themselves: Kathryn and Chris Johnson are setting an example for us all of what can be done, how their home represents their values, and after competently accelerating up the learning curve, happily sharing their knowledge with the world.