The High-Performance Home, Part 2: The Smart Wall
Rona Easton and Lonn Combs of EASTON+COMBS, the award-winning architectural office based in New Marlborough, Mass. have allowed Rural Intelligence to look over their shoulders (and those of their client) throughout the construction process of a high-performance home going up right now. This is the second installment of eight (or so — this is construction, after all) in a series that is giving us a lens into the building of an energy efficient house in Egremont, Mass.
Framing is going up fast.
By Rona Easton and Lonn Combs
“As I get older, I’m trying to simplify things,” our client has said, and that sentiment informs everything we do as architects. As the house framing quickly goes up, our focus turns to walls and the challenge of this mantra of simplicity within the complexities of construction.
Walls are a lot more complicated than you may think. Of course, they provide shelter and enclosure, but now they do a whole lot more and so they’ve had to step up their game and get really smart. As mediators between the outside environment and our heavily controlled interiors, walls need to multitask like never before, while also being aware of what is required of them in different seasons and climates, and being able to behave accordingly.
The rules of the game changed even further with the advent of airtight, heavily insulated buildings designed to stop the escape of energy. With thicker insulation, moisture moves through more slowly and the air tightness closes down the escape routes. Controlling moisture and preventing mold buildup is the fundamental challenge of our new, high-performance walls.
Mockup built to study wall assembly.
In the Egremont house, the exterior walls are over 16” thick, comprised of several important layers. It is hygroscopic, meaning that any moisture that gets in will be controlled and dispelled. You can think of it as a modern hiking or skiing jacket — it insulates and protects from rain while also breathing and allowing moisture to escape. It does this through several well-considered layers: thick insulation between the 12” vertical joists, smart membranes (high-tech membranes that know which way the moisture wants to move and know when it should be blocked or allowed to pass), and a ventilation space between the wall sheathing and exterior finish.
With such a thick wall, and so many layers performing different, essential functions, the I-joist structural system brings simplicity where there would otherwise be even more layers, most typically a double stud system which is essentially a typical timber framed exterior wall built twice, one outside the other.
Left: Garage/studio building. Right: Interior of the studio.
The I-joist system is also very builder and engineer friendly. Jason Smith of Frame to Finish, the sub-contractor to our GC, Little Deer Construction, loves this wall. With considerable expertise in traditional and advanced framing, he was thrilled with the ease and speed of erection, and the straightness and stability of the frame. There was no need for him to provide the usual temporary bracing to prevent the frame from buckling. Our structural engineer, Chad Lindberg of Taconic Engineering, loves the structural efficiency of the I-joists as wall studs, and the creative solutions this allows him.
Framing is up in the main house and trusses were erected in less than two hours.