Wind, rain, heat, humidity—every year New York buildings withstand extreme conditions throughout the seasons. Now multiply this weathering by 113 years, and then try to turn that structure into a well-sealed Passive House.
We touched base with Jordan Goldman (Zero Energy Design) to get an idea of the critical air-sealing challenges that had to be overcome as they brought a 19th century row house to PH standards. Lead designer Julie Torres Moskovitz (Fete Nature Architecture) of the project—known as “the Tighthouse”—then filled in some of the details on the acclaimed retrofit ahead of tonight’s talk at the Center for Architecture.
Goldman explained that the rough, irregular shape of an eroded existing building makes taping, caulking, and sealing much more difficult than in new construction when everything is square, level, and smooth. And there is no option of pouring a new concrete wall, a very effective air barrier that can simplify the detailing.
There is no general prescription for air-sealing existing buildings since, as Moskovitz found in the research phase for Tighthouse, each condition is unique: landmarked rebuilding or new infill, wood frame or masonry? However, there are some common approaches. “One would be to use a liquid-applied air barrier on the inside of the masonry structure,” Goldman explained. “Another would be to use an air-barrier membrane with all of the seams taped. This should be installed on the interior side of a framed partition that is inbound of the masonry. Then, a second service chase is installed inbound of the air barrier membrane to avoid penetrating the membrane for plumbing and electrical. In either approach, the air barrier must be sealed to all of the joists to avoid air leakage where they sit in the walls.”
With luck and hard work, the air-sealing efforts pay off. Moskovitz recalled “one of the most memorable periods of the project construction was during a preliminary blower door test.” After PH-certified windows and doors were installed, the Tighthouse was at a not-so-tight 1.5 air changes per hour (ACH) at 50 Pascals. While Moskovitz’s PH training in Dublin told her that a smart vapor control membrane and tape around the windows would increase airtightness, other team members were not as sure. As an experiment, she and the owner installed an Intello membrane and Tescon Profil tape around one window. “Then we all stood together inside the home during the blower door test and saw how the tape was holding back air infiltration while we could feel leakage around the other windows and doors. This convinced everyone that we should go the extra length.” The next blower door test showed 0.6 ACH at 50 Pascals, and finally 0.384 ACH at 50 Pascals after all the bells and whistles were added, earning the Tighthouse project its name.
Learn more about how the pioneering Tighthouse retrofit was achieved tonight at the Center for Architecture.