New Yorkers, Start Your Blower Doors: It's Blower Door Day


We're happy to proclaim October 3rd Blower Door Day - here at our headquarters, in Brooklyn, New York - as the new residential building energy code requiring blower door testing at 3ACH50 comes into effect.  As we noted in May, of course New York isn't the first to adopt the 2015 International Energy Conservation Code and keep the blower door requirement intact - while many states have eliminated the requirement in the process of adoption - perhaps New York is one of the more significant states to require a blower door test (our bias makes us think so...).

We Can Measure It - So Measure It

We all understand that durable airtightness is the cornerstone of energy efficiency, comfort and resilience.   (Following the devastation of Superstorm Sandy, 475 Cofounder Ken Levenson wrote Building Efficiency and Blower Doors: Essential Responses to Sandy - making the direct connection to our resilient future.)  The codes previously have required airtight construction, but mostly just in theory - not in practice - simply because a test was never required to physically verify it.  Most of the time this meant that projects didn't come close to the intended airtightness limit.  As of today, all residential construction in New York State, must be physically tested and verified with a blower door.

A New Age In Application Of Building Science

Cynics may note that the 3ACH50 is far from Passive House requirements of 0.6ACH50; that it's not mandated in the commercial code, and that compliance is likely to be scattershot at best.   Don't be fooled.  THIS IS A BIG DEAL.  Like doctors working with simple tools like thermometers and blood pressure monitors,  using a blower door is a fundamental tool to evaluating a building's proper construction.  As the application of modern medicine moved from leeches and prayer, to blood testing and diagnosis, building science is moving to the construction site, from the dark ages, to modernity.   Mandating the use of the blower door is part of a larger movement, not just out of the dark ages, but toward a high-performance, more comfortable and a carbon free future for our build environment.

Toward Passive House

Make no mistake - this is another important step toward making Passive House normal.   As we demonstrate, at a mass market level, the utility and benefits of verified airtightness the logic of even tighter testing code requirements will be more easily made.  475 has worked and continues to work, to make the case for airtightness. Cofounder, Floris Keverling Buisman was proud to sit on the 2016 NYC Department of Buildings Energy code update committee whose work also resulted in the NYC code now also mandating that commercial buildings sized between 25,000 and 50,000 square feet must be blower door tested (C402.5.1.3 Air barrier testing) with a maximum of 0.04CFM/sf@75 envelope leakage. This is big step toward testing all buildings - and only the second City in the USA (after Seattle) that requires blower door testing for commercial buildings.

These mandated tests are great leaps forward in NYC and New York State. Leading to direct and permanent carbon reductions for buildings constructed or renovated after this date.

Find Out More



Urban Green Council has an excellent series of videos introducing the new blower door requirements: HERE.

Please note that this video uses canned sprayfoam as the go-to product for airsealing. You might get to the required 3.0ACH50 when doing a blowerdoor with that approach, but it is unlikely you will go beyond that target. Additionally sprayfoam is not a durable or sustainable airsealing method - You can do much better and build tighter with 475's reliable Proclima airsealing system.

Code Seminars:

Urban Green Council also has a great seminar series called Conquer the Code - of which Ken Levenson was glad to participate on the Advisory Committee - where attendees find out not only about airtightness but a comprehensive look at the new energy codes and the building science underlying them.  See the schedule HERE.

475 Training:

The 475 Make it Tight 4 hour seminar shows that path to Passive House performance:  building science, materials, design, construction and testing.   Attend an upcoming Make It Tight seminar by checking the event page HERE.

Code Text:

  • You can see the NYS code language here.
  • And the similar NYC code language here.
  • Get an overview from 475 here.

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