Jersey City’s First Certified Passive House is a Carefully Considered Retrofit
This article is a reblog from part 3 of a series from Jersey Digs.
We're seeing exciting updates from the architects at Mowery Marsh and construction management team of Brinton Brosius, with building science and Passive House consulting by Levy Partnership. In the newest of a series of blog posts on Jersey City's first certified Passive House project, they cover the air sealing details. This is a wood frame retrofit (download our free Wood Frame DER details here), with some complicated air barrier connections - and this team takes its time to ensure they're sealed up right. They take a belt & suspenders method of sealing both the OSB sheathing with TESCON VANA, and covering the sheathing with airtight, vapor-open SOLITEX MENTO 1000. Doing this will not only ensure the best case for the blower door test, it's going to ensure long term protection from vapor and moisture problems for the long-term life of the building. That's a bonus, on top of occupant comfort benefits (a goal of the project).
Air sealing is the one process that adds the most time to a passive project when compared to a traditional build. However, it’s a critical step toward a Passive approach and ultimately the payoff will be huge, not only in heating and cooling costs but also the level of continual comfort within the home.
Another fundamental aspect of the project that makes this project exemplary: dedicating team members and labor hours to focusing on the air barrier.
For this project, a subcontractor is brought in, whose main focus is insulation and air sealing to make sure it’s a thorough installation since it’s so critical.
If your air barrier is an after thought, you don't make 0.6ACH50. Or if you do, it costs far more than you hoped for to get there. One of the best ways to ensure you hit your numbers on first pass, is to make it someone's job. The air barrier needs forethought and protection from any subcontractors that may not be on the Passive House path.
This consideration plays out particularly clearly at the floor joists:
On the interior, the air sealer uses a product called Intello which provides airtightness that also controls vapor and can act as a membrane for the insulation. This installation is where the job can get tedious and the extra efforts really pay off.
The contractor cut around each floor joist and installed the Intello Plus around the seams, which will connect continuously between floors. The insulation can then be installed into the open bays, with Intello coming down to connect to that joist sealing transition with just one piece of Tescon Vana tape across where the wall meets the floor. That kind of connection cannot happen without someone there to consider the staging and plan the connection.
Yet another point in this article where we agree:
In harder to reach places, closed cell spray foam insulation is used to act as the air barrier. It is not used everywhere because it can shrink in the future and cause leaks at its perimeter.
We once pondered Is Foam Evil? We're not in a place where we can always have a purely foam free building. That said, sometimes in tricky retrofit situations, you might need to weigh the lesser of evils. When you do, it's important to remember that spray foam should not be depended upon for long-lasting airtightness or continuous thermal insulation.
Stay tuned for the upcoming blog series at Jersey Digs.