Bringing Passive House Leadership Down South
REdesign.build is a design-build firm based in North Carolina led by Will Alphin, a firm with a reputation for making innovative, elegant, modern homes in the South, winning numerous prestigious awards over the years. Alphin had been putting together a residential development of four homes to sell and saw it as an opportunity to experiment with Passive House and high performance design at his own discretion. After some years of sharing notes from the passive house movement in the northeast, Alphin brought architectural designer and CPHC, Dylan Buonfrisco, on to the RE team to lead the design and construction of the development and help advance a high performance building movement in the region. Alphin and Buonfrisco saw Passive House as the next logical step toward optimized sustainability, raising the values embedded in the work and, as well, an opportunity to disrupt the North Carolina marketplace.
REdesign.build is now in the home stretch of completing the first of four 3,500 sq ft homes, which aim to be the first PHI certified buildings in the region and will be equipped with solar and battery storage bringing them to net-positive levels. With the learning-curve overcome in the first house, the plan is to keep the momentum going on the next three, improve process efficiencies, and cost effectiveness, while continuing to focus on expanding the Passive House market in North Carolina.
Project designer and Passive House consultant, Dylan Buonfrisco helped guide the enclosure and systems design. With a clear goal of simplicity and durability - the enclosure is anything but typical. The walls are wood framed but with 9 ¼” gluelam timbers two stories tall, widely spaced, giving it the feel, initially, of a heavy timber framed house. This deep balloon framing not only allowed sufficient insulation for the climate but the technique let them simply maintain air and vapor control continuity between the floors in a simple and elegant manner - with the application of a ledger over the inboard membrane to support the second floor.
A, B, Cs, of Smart Enclosure Construction
The wall assemblies followed best practice, using the INTELLO PLUS airtight smart vapor retarder membrane inboard of the framing and waterproof vapor-open SOLITEX membrane outboard. At the interior a service cavity was provided with metal furring strips, for wiring and plumbing and outlets, dramatically limiting the number of penetrations through the control layers. Dense-pack cellulose was blown through the INTELLO PLUS providing R-35 insulation level. A gypsum board finish was then applied to the furring. Similarly, outboard furring strips were applied the then siding forming a back-vented rainscreen facade.
With airtightness surrounding the fibrous insulation, smart vapor control inboard and sufficient drying potential outboard - the enclosure is built to last.
The roof was similarly constructed but achieving R-45 insulation value and finished with a low-slope, standing-seam metal roof over a 3” ventilated cavity SOLITEX membrane.
Windows Get Inside-Outside Treatment Too
Understanding the critical nature of continuity - the inboard INTELLO PLUS and the outboard SOLITEX membranes were connected to the window frames with TESCON VANA tape - preventing indoor conditioned air from reaching condensing surfaces in winter, preventing insulation wind-washing, while also allowing any moisture in assembly to dry out.
Don’t Forget the Shading
Exterior shading is a critical aspect of Passive House all-to-frequently ignored - to the detriment of occupant comfort and cooling loads. In the South, the stakes are even higher. So REdesign.build took this requirement and turned it into a design feature with steel brissolies, overhangs and decks.
If you’re building higher-performance buildings you should always be doing blower door tests - it’s like getting your car inspected or your blood pressure measured. It’s basic. Luckily, when you’re going for Passive House certification you can’t talk yourself out of it. While the REdesign.build team has not yet performed a final blower test, they were able to hit an impressive 0.43 ACH50, on a pre-drywall test, which was done before the SOLITEX was sealed to the exterior side of the windows - well within the certification limit of 0.6 ACH50. The team, still pushing for tightness, expects to come in at least a little bit tighter for the final test.
What’s Next? Cut to Video
REdesign.build sees great opportunity for Passive House in the South with the promises of greater quality and comfortable indoor environments. Alphin also points to other experienced builders, as guiding stars, who have seen cost differences tighten between standard construction and Passive House as experience grows with each project.