Karuna House – airtight envelope and modernist aesthetic demand precise construction

Passive House/Minergie-P standards combined with Holst’s design mean tight tolerances.

While I’m sure that Hammer & Hand’s carpenters think modernism is cool, I’ve got to believe that one of the main reasons that they love to work on modernist structures is that they take such pride in their work.  Modern design, unlike more traditional forms of architecture with goof-hiding trim and molding, is uncompromising.  Each element of a structure needs to align with the next perfectly to carry off the clean lines and strong geometries found in modernism.  Gaffes are obvious and aesthetically disastrous (if not worse).  Good modernist construction requires excellent craftsmanship, and our carpenters are justly proud to build modernism right.

The same story holds true for Passive House construction.  Again, there’s no question that our carpenters are deeply motivated by the planet-saving nature of Passive House.  But the hunger for precision is also fed by these projects, with their airtight envelope construction and make-or-break blower door testing.  Passive House builders rightly boast with one another about the level of airtightness they’ve achieved on various structures.  After all, it takes high levels of craft and attention to detail to break Passive House’s airtightness barrier (0.6 air changes per hour at 50 pascals).

Hammer & Hand team at Karuna Passive House.
Hammer & Hand’s team at Karuna.  Photo by Aaron Bergeson.

So combine modernist perfection with one of the most ambitious Passive House projects around and what do you get?  The Karuna House, designed by Holst Architecture and being framed right now by Hammer & Hand.

Karuna Passive House construction.
Recent progress at Karuna.  Photo by Scott Gunter.

“We have to be forward-thinking when we’re framing Karuna because we need to be thinking about its precise finish always,” said project supervisor Scott Gunter.  “The finish is so key to the project that we’re not working from framing dimensions.  Instead we’re doing all of our work based on the finish dimensions.  It takes a lot of math, but it forces us to think in terms of the final product.”

The precision demanded by Karuna means very tight tolerances during construction, less than 1/16 of an inch, starting from the ground up.

Karuna Passive House construction

More progress at Karuna.  Photo by Aaron Bergeson.

“Everything is absolutely plumb, level and square,” said Scott.  “We’re constantly back-checking and cross-checking everything on site as we build to ensure that it’s all as close to perfect as a human being can make it.”

The reach forklift pictured in the short time-lapse video above allowed the team the luxury to pre-assemble an entire 30′ long wall for the home’s guest wing and then lift it into place.  The wood you see is FSC® (Forest Stewardship Council®) certified.  Framing lumber is kiln-dried to less than 19% moisture content.

The team will be using lots of cool framing and flooring systems, including locally-processed engineered wood, open web trusses, and lots more.  So stay tuned for the next Scott Gunter-hosted video showing what’s coming.

– Zack

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