Passive House (Passivhaus) building envelope demands dry conditions during assembly.
Looking like a huge present wrapped in white, the Karuna House green home building project has officially entered its cocoon phase, with the structure now fully enveloped in protective tenting.
(NOTE: The Karuna House, designed by Holst Architecture and built by Hammer & Hand, seeks PHIUS+ Passive House, Minergie-P-ECO, LEED for Homes Platinum, and net zero energy designations. Learn more at our Karuna House page.)
The Karuna House, before tenting (l) and after (r). (Before photo by Mitchell Snyder Photography. After photo by Hammer & Hand’s Shelley Martin.)
As mentioned in our post about the “topping out” ceremony at Karuna last month, the tenting of buildings during construction is standard practice in Europe, though still quite uncommon here in the US.
The practice offers several key benefits for a project like Karuna.
First, it allows the entire structure to dry out, and stay dry during critical phases of envelope assembly and construction. Project supervisor Scott Gunter told me that after just two weeks under the tent, the moisture content of the framing lumber at Karuna is already down to the 19% required by code before “drying in” – the closing up of wall assemblies – is allowed.
“We’ll easily be below 19% by a couple percentage points by the time drying in happens in a few weeks,” Scott said.
The tent/scaffolding system also gives carpenters and subcontractors 360-degree access to the entire building envelope, and allows them to work dry and relatively warm thanks to the tent’s incidental greenhouse properties.
“Our subs are so impressed when they drive up to the tented structure,” said Scott. “Last week the roofer was thrilled to have that kind of access, completely dry. And it’s great for our guys, too. It’s been cold and wet out there, so the tent is great to work in.”
It will stay up into August or September. Because the building envelope is so tight, a big downpour in August would cause major problems to the structure were it not protected from the elements.
Construction at Karuna continues to progress well, with installation of the wet flash barrier currently underway. We’ll have more on that process soon. Thanks for reading!
– Zack
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