An article by Bruce Sullivan
There’s a myth circulating that super energy-efficient homes cost more to build than homes with typical code-level energy features. Last year, Architect, Richard Pedranti, busted that myth by designing a home to Passive House standards for only $165 per square foot. “We typically use between $175 and $200 per square foot for standard new home construction costs in our area,” said Pedranti.
For that modest price, this Passive House offers three significant benefits: personal health and comfort, superior energy efficiency, and affordability.
The 2,153 square-foot home achieved this with a simple design, lots of insulation, super air sealing and modest package of mechanical equipment. The result attracted quite a lot of attention, including the 2017 Passive House of the Year award and several magazine articles.
The Scranton Passive House is the 112th Passive House certified by the Passive House Institute, US. Pedranti produced a free e-book (PDF) packed with photos, detailed drawings, and useful information on this extraordinary home.
The Passive House program has had immeasurable impact on the North American housing industry by raising the bar for energy efficiency. The organization has set a very high standard of energy performance, trained thousands of professionals, stimulated a growing market for high performance building materials and equipment. Pedranti has managed to meet these high Passive House standards with a home that is cost comparable to similar standard homes in the area.The idea that high energy performance comes at a high price is a persistent myth. Its been clearly established that zero energy homes cost less to own. They offer consumers buying power for immediate return on investment from the very first month. The investment is supported by higher market value. Everybody wins!
As with most Passive House designs, simplicity is key. The building envelope is a two-story rectangle. The first floor has an open kitchen, dining, and living space along with a mudroom, office, powder room, laundry room, and mechanical room. The second floor has 3 bedrooms, 2 baths, and a den. A generous front porch on the north side of the home connects to a large screened porch on the northwest corner. These outdoor spaces add a bit of architectural interest and gracious living without complicating the insulation or air sealing details. An arbor across the south side provides summer shading and a porch overlooking the neighborhood. Because the roof of the main house was shaded, the garden shed to the northwest of the screened porch will accommodate solar panels to produce enough on-site energy to achieve zero energy status when the owners are ready.
“I knew when I got into Passive House, there was a hard learning curve, which has everything to do with the fact that you measure things. That’s not the case with a typical, prescriptive code-built home,” said Pedranti. “With Passive House, you create an energy model with a spreadsheet. It’s very detailed. Every bit of material, the design, the orientation of the windows—all that stuff is either ‘yes’ or ‘no’ in terms of meeting the requirements. For me, it’s well worth the extra effort because we make better buildings that are healthier, more comfortable and cost less to operate”
In typical homes space heating and cooling are the biggest categories of energy use, followed closely by water heating. Today’s super energy efficient homes turn this relationship upside down. The energy breakdown for the Scranton Passive House shows that a whopping 67% of the energy is used for the lights, appliances and other devices that draw power from wall outlets, collectively known as “plug loads.”
All that efficiency adds up to significant dollar savings. If this home had been built to code, it would have cost $233 per month for energy. Instead, the monthly bill has averaged $67. With $166 per month in additional buying power, the owners could qualify for a mortgage that is about $32,000 larger. While it’s impossible to say how much the same house would have cost without the Passive House features, these savings go a long way to funding the energy saving features.
To achieve these savings, Pedranti designed raised heel roof trusses that allow R-85 ceiling insulation that extends all the way to the exterior walls. Walls are framed with I-joist studs providing enough depth for R-61 insulation. Many Passive House projects use up to 12 inches of expanded polystyrene (EPS) below a slab-on-grade. Instead, this project uses perlite, a natural mineral with insulating qualities. “It has an R-value of 3.5, is environmentally safe, and it is made in nearby Bethlehem, Pennsylvania,” said Pedranti. “It comes in 8-inch bags. Our slab went from R-40 to R-75 at very little cost. I never realized it could be that easy.”
Window area and placement was carefully designed to balance heat loss and heat gain. Most of the windows were placed on the south side to maximize heat gain in winter and reduce overheating in summer. Super-efficient R-7 Eforte windows were purchased from Intus.
While thick insulation increased the cost for the thermal envelope, the entire mechanical system cost only $5,000. This included the 9,000 btu mini-split heat pump, heat pump water heater and energy recovery ventilator. This illustrates how high-performance homes shift cost from large mechanical devices that require large amounts of energy to use to structural features that reduce energy use.
“This was my first super energy-efficient project. It was a very positive and exciting direction in which to take my business,” he said. “I have found over the years that a lot of the bad things in our industry are the result of an overemphasis on pure aesthetics. I really like that Passive House is based on science.”
Richard Pedranti Architect (RPA) is a full-service architectural firm serving the Upper Delaware River Region, as well as Philadelphia and New York. RPA specializes in Passive House and high-performance buildings putting modern building science to work creating beautiful, healthy, comfortable, and energy-efficient buildings.