Walk into Brookfield Residential’s Midtown Residence Eight, just outside of Denver, and you’re embraced by sunlight and warmth. You’ll notice that street noise is muffled. Your first thoughts likely won’t be “this is a green home.”
Yet Residence Eight is the very first home certified by the Passive House Institute U.S. (PHIUS) in the state of Colorado. What’s more, it’s the first certified Passive House by a production builder in the United States. The home earned Brookfield a Gold Award in the green category of NAHB’s 2014 Best in American Living Awards, as well as an honorable mention as Project of the Year for single-family production houses.
Performance standards didn’t compromise design. At Residence Eight, performance partners with design, enhancing a beautiful home. KGA Studio Architects, who designed Brookfield’s Passive House, got involved in the project when Brookfield requested bold architecture that would break the mold of traditional merchant housing. Ultimately, says Jerry Gloss, principal at KGA, the design process for the home would take longer than its construction process. The group’s teamwork meant performance and design didn’t have to compete. “To succeed, there had to be a willingness to keep an open mind. There are no absolutes in this,” Gloss stresses. “You can’t have a ‘We always do it this way’ attitude. Everything is up for reconsideration.”
Per Passive House requirements, the home features a super-insulated exterior envelope. (A standard Brookfield home uses 2x6 advanced framing and a cellulose-fill cavity, with 1 inch of spray foam applied to the inside.) To meet PHIUS benchmarks the Midtown Passive House instead used a double stud system (For more on Passive House criteria and stats on the home, see sidebar.)
Construction is more traditional than you might assume. While many Passive House designs tend to be boxy, this one isn’t, explains Duncan Prahl, senior building performance specialist at IBACOS, the home building innovation company that served as performance consultants for the project. The floor plan uses classic design elements, taking a Passive House and making it feel more familiar. A traditional master bedroom is set over the garage, and a small portion of insulated roof on the first floor is offset from the walls. While the more traditional design moves added complexity to energy modeling and calculations, their design value was important.
“Your normal Passive House is built internally, and insulation is applied to the outside like a jacket,” said Graham Swett, associate at KGA Studio Architects. Residence Eight didn’t stick to this ‘typical’ Passive House build plan: by breaking away, it helps make Passive attainable.
Glazing drove design and performance decisions. Though Residence Eight fits into the overall design scheme of Midtown, one thing that pegs it as a Passive House is fewer windows than in surrounding houses, notes John Guilliams, director of design at KGA. The design team for Residence Eight was faced with the need to complement neighboring homes, whose designs featured many smaller windows scattered through the façade, while still keeping performance numbers high. The design team set windows at the home’s south and west faces, taking advantage of natural heat and light from the sun. By using a window with an exceptionally high insulation value, KGA earned greater design freedom, and the team was able to place more windows in the home, maximizing daylight and ensuring an open, airy atmosphere.
Once a window product was selected, the team faced more choices.
- Operable versus fixed. Most of Residence Eight’s windows are fixed because of air infiltration concerns. The team evaluated each individual window opening, asking whether the window could best meet performance and design goals as a fixed or operable unit.
- Inset versus standard installation. As any high-performance maven knows, careless window installation cancels out the energy savings you gain by a performance product. The double wall system complicated the picture. Windows at Brookfield’s Midtown Passive House are inset to the inside face of the exterior 2x6 wall, creating a “dead-air” pocket and increasing the effective insulation of each window opening. The inset window configuration required a sloping sill to move “bulk water” to the exterior face of the building. A framed-in buck was also built around the whole window opening. Attention wasn’t spared on flash and tape details: lots of tape and DuPont Flex Wrap NF tie into the Tyvek DrainWrap.
- Mock-ups ensured accuracy. To answer durability and performance concerns, the team did a full-scale window installation mock-up in the garage of the home before installation moved forward. This helped everyone understand flashing, potential water intrusion, and the importance of correct installation at each opening.
Mechanicals were scrutinized. Passive House standards force mechanical decisions to the top of the priority list. While the home uses extremely efficient systems (see sidebar), to squeeze even more performance out of the building’s envelope, the team made sure there were minimal perforations in the exterior wall. The fewer holes punched through the envelope, the better the home’s insulation and airtightness, with less energy needed to heat and cool the space. Brookfield carefully measured each room’s supply register CFM rates against the house as a whole to ensure a balanced ventilation system and check for leaks.
Plan ahead and insist on good communication. By studying the home’s energy requirements before the design phase began, everyone knew the goals and planning proceeded smoothly. “The average house construction involves 30 to 35 different trades,” says Brian Stamm, manager of production planning at Brookfield. “You have to communicate very clearly to everyone involved,” from draftsmen to component suppliers, he says. Shoehorning performance into a project after the fact results in frustration and missed opportunities.
“People have come from all over the country to see our product,” says Stamm. By making a home that captured the widest audience possible with its design, and encapsulated incredible performance within that comfortable environment, Brookfield scored a win in the market. “Participating with Passive House allowed us to broaden our perspectives and to strut a bit,” Gloss said. More important, he says, everyone came away from the project with an increased sense of urgency.
Fresh from the Passive House experience and looking forward to the new codes on the horizon, KGA Studio Architects developed KGA University, which facilitates learning inside the firm and prepares team members for new realms of home performance. “At some point the industry will be forced to wake up and realize these changes, and it won’t necessarily be on a volunteer basis,” warned Gloss.
Swett agrees, noting upcoming residential codes that will mandate mechanical ventilation. “The new world of housing could look very much like buying a car, with each home featuring a sticker disclosing operational costs. America is starting to pay attention.”
The real value of a house is whether it will resonate with a buyer and become a home. In addition, the real value of a highly efficient home is found not just in just what a homeowner saves per month on utilities, but in the home’s resale value. Creating a beautiful product and enhancing it with efficiency resulted in a winning home for the future.
Amanda Voss, MPP, is an author, editor, and policy analyst in Denver. She has served on the board of Energy Literacy Advocates, spent six years in residential construction, and has taught AIA classes on fenestration.
Meeting the Passive House Standard
A Passive House must meet three main requirements, per Passive House Institute U.S. (PHIUS) criteria: :
- No greater than 0.6 air changes per hour at 50 pascals (<0.6 ACH 50).
- Heating and cooling cannot exceed 4,755 BTUs per square-foot annually.
- Specific space heating demand: Alternately, heating load cannot exceed 3.17 BTU per square foot per hour.
- Specific useful cooling energy demand: Cannot exceed 4.75 kBTU per square foot per year.
- Energy Usage: Maximum total energy use cannot exceed 11.1 kWh per square foot for heating, cooling, domestic hot water, auxiliary, and household electricity.
Efficiency at Residence Eight
- Passive House Institute U.S. (PHIUS); U.S. Department of Energy Challenge Home; ENERGY STAR Home; Environmental Protection Agency Indoor airPLUS; WaterSense
Double wall construction; a 2x6 exterior wall
2x4 framed interior wall
2x6 wall is flashed with 2 1/2” of closed cell spray polyurethane foam and dense- packed with netted and blown fiberglass fill
OSB (oriented strand board) and 1” of XPS foam on exterior, covered with Dupont™ Tyvek® DrainWrap™
Special styrofoam was used to resist Colorado’s expansive soils
Above-grade walls have values of R-51; basement wall insulation is R-47.5 with the slab rating an R-20
Passive sub-slab soil gas mitigation system in response to brownfield location
Alpen High Performance Products 9H and L; average U-factor of 0.15
Navien water heater and boiler that learns the usage patterns of the residents, anticipating demand for hot water to avoid wasted BTU's
Zehnder Energy Recovery Ventilator (ERV)
1.2 kWh of DOW POWERHOUSE™ Solar Shingles