Foam-Free Air Sealing for Energy-Efficient Buildings

Presentation of air sealing strategies for high-performance buildings without relying on spray foam or rigid foam insulation.

+Ken Levenson presenting foam-free air sealing techniques for a NYC townhouse with interior insulation and a continuous “smart” vapor-retarding air barrier.

This technique is important for Passive House retrofits and should be considered best practice for any gut rehab of a brownstone where exterior insulation isn’t practical. Air tightness eliminates drafts for better comfort and reduced energy bills. It also prevents moisture buildup from condensation that can lead to mold and structural damage. Add filtered fresh air ventilation with heat recovery to optimize indoor air quality and energy performance.

Exterior insulation is preferable from a building science point of view. New buildings should be airtight, allow drying to exterior and to interior, and have exterior insulation.

The following example for a brownstone retrofit can be modified for new, non-combustible construction as well:

Integrating a window in the airtight layer – brick/brownstone retrofit case

Brute Force

My colleague in the Pacific Northwest, Mike Eliason, at Brute Force Collaborative, has shared his perspectives on the recent split between the Passive House Institute US (PHIUS) and the international Passive House Institute (PHI), based in Darmstadt, Germany.

As an architect with credentials from both institutions, I hope the two parties can reconcile and work together in the future. Meanwhile, the benefits for homeowners and developers of building to the Passive House standard remain unchanged. Lower utility bills, reduced noise, and better indoor air quality are just a few. And for a variety of reasons, this energy-efficiency standard works especially well in New York City.

If you follow my tweets (@DuncanArchitect), you know that I sometimes spend my Sunday mornings reading German Forschungsberichte from PHI instead of going to brunch. This particular research report detailed six years of monitoring the energy use in a school built to the Passive House standard. The report confirmed scientifically that a frost skirt can allow for less sub-slab insulation. Short term monitoring and lab experiments had previously suggested that this was true, and these findings are already incorporated in the PHPP energy modeling software. Real-world monitoring to confirm the assumptions made in energy modeling software is important, and I’m glad to see that this monitoring validates the accuracy of PHPP.

The bottom line is that the scientific basis of Passive House is strong and the rift between PHI and PHIUS won’t prevent people from being able to have a certified Passive House building with lower utility bills, reduced noise, and superior indoor air quality.

Email Greg Duncan at for more information.

Multifamily Passive House Buildings in New York

The most obvious benefit of the Passive House standard is a dramatic reduction in energy costs. Using the Passive House design methodology and energy-modeling software, architects can save building owners up to 90% on heating costs compared to a typical existing building. In addition buildings built to this standard have superior thermal comfort—warm in winter and cool in summer with no drafts. A side benefit of using high-performance windows and air sealing is reduced noise from the street and from neighboring apartments. The proper architectural details can provide for acoustic insulation and energy efficiency.

Rental Buildings

Due to the expense of submetering and market expectations, owners of multifamily rental buildings in New York usually pay for heating their tenant’s apartments in addition to the common areas. By law landlords are required to provide heat between October 1 and May 31. This can be a significant expense, so developers often ask their architects to design energy-efficient buildings.

Condo Buildings

Tenants in condominium buildings often have their own heating equipment in the unit and are responsible for their own heating bills. One of the reasons condo buyers are attracted to green buildings is that they can save a lot of money on their utility bills. If the energy savings are significant, as with a certified Passive House building,  the developer’s initial investment will pay off with a higher sales price.


As an architect who has worked on townhouses in Brooklyn and Queens, as well as larger apartment buildings in Manhattan, Gregory Duncan understands the potential this type of building has for huge increases in comfort and energy savings. See our article on Passive House in New York City which explains how this green building standard is in many ways easier to achieve in New York than many other places.

Of course, the Passive House energy-efficiency standard applies to commercial and single-family houses as well. So, no matter what building type you are planning, a Certified Passive House Designer can help you make it better.

Email Greg Duncan at to get started.

March 15: Passive House Presentation

New York Passive House (NYPH) is hosting an event on March 15, 2011. Jotte Seghers will present some Passive House projects he has worked on in Belgium including a multifamily apartment building, a school, and an entire neighborhood. For those who are new to the green building standard, I will present “Passive House 101” with a focus on insulation.

The Passive House standard is growing quickly in New York. NYPH was founded in 2010 and now lists 15 projects on its website.

A recent study of Passive House homes in Germany showed that these houses cost 95% less to heat than typical older buildings. The article is in German, but here is a link to it via Google Translate.

Please RSVP so that security can let you into the building.