Tight Historic Masonry Rowhouse Renovation by Caliper Studio
On Prospect Avenue in Brooklyn, NY, Caliper Studio's gut renovation of a brick brownstone rowhouse used what has become the typical Passive House project approach: very good triple-pane glass windows, thermal bridge free LAMILUX skylights, and a interior insulation with cellulose and Pro Clima INTELLO membrane as the smart vapor retarder and air barrier.
We had the opportunity to get into the details of this project and be a part of the blower door testing. Let's take a look at the finer points of this deep energy masonry retrofit project.
Mechanicals: Mitsibishi air cooled split heat pumps, provide the supplemental heating and cooling in this house - installed by Bright Star Service and ducted to provide small amounts of heating or cooling to each room. Two Zehnder central HRVs provide the heat recovery ventilation - one in the basement and one in the top floor - one per apartment.
Airsealing and insulation:
The house uses the construction details that 475 has developed for masonry interior insulation and airtight construction as a base-line for the design. It was great to see the interior rafter extenders in the ceiling (see photo on right), that allow additional cellulose to be used under the existing original roof deck and allow the construction of a foam free flat roof.
The wall's original plaster (airtight!) was left in place and additional plaster was added between the floor joist, at spots that were covered by the original crown moldings and baseboards (see image on left). The plaster around the joist was treated with TESCON Primer RP and then taped with TESCON Profil. In the photo on the left you can see the slightly darkened plaster shows the primer and the taped joists (don't forget to cut back the floor, so you can tape the top of the joist).
INTELLO Plus was then installed by Lloyd's crew of NY insulation & airsealing from the bottom of the basement walls, up past the cut back floors on the front and the back of the exterior walls and then wrapped below the roof insulation as well. All seams were taped with TESCON VANA or UNITAPE. This created a continuous airtight shell with smart vapor retarding properties for the entire insulated enclosure.
Connections to the plastered walls were made by adhering the INTELLO Plus to the sometimes uneven plaster with non-embritteling/form fitting adhesive CONTEGA HF (or as Lloyd calls it, "green gunk").
Windows sealing
The triple-pane, tilt-and-turn wood windows (by Cembra/Rieder), were installed after the INTELLO Plus was folded into the plywood window boxes. This made airsealing the wood frames of these windows by taping them with TESCON Profil much easier. Lloyd used the pre-folded corners of Profil tape to make sure that even the smallest leaks in the window corners were prevented. It does take more time than sprayfoaming a window, but with some experience you can tape a window within 5 minutes and know that you made a long lasting/durable airtight connectoin at that important intersection.
Lessons learned
The plastered walls, original and infill worked very well. During the first blower door test a few missing plaster patches were discovered, for example behind a parallel beam (at neighbors fireplace location). The contractor was then able to correct these omissions.
Additionally there were 2 exposed brick fireplaces on the party-walls. Normally this would lead to a lot of leaks, which it did during the tests. However, after pointing the brick and coating it with Benjamin Moore "Super-hide - latex semi-gloss enamel" the majority of those leaks were sealed. The question remains if that is a durable airtight seal.
Final Blowerdoor test
The final blowerdoor test on November 29th resulted in a 457 CFM flow to reach 50Pascals. This converts with the conservative interior volume of the building 29,000 cu ft to a 0.94 ACH50. A great result for both Caliper studio, NY Insulation & airsealing, and a great case study of the 475 airsealing details.
We're excited to offer you a solution for your high performance townhouse gut renovation - if your goal is EnerPHit or just a very comfortable low energy building.
