January 10, 2012

EcoBrooklyn Harlem PH project – airtight

The first project under construction (and now finished) in Manhattan that is using the

Front of 130th street with triple pane windows

Passive House construction methods and PHPP to calculate it’s loads is on West 130th street in Harlem.

Gennaro and his crew from Ecobrooklyn, as per their company philosophy used reclaimed materials or rapidly renewable material were they could, but to make the building truly sustainable used energy saving/durable materials where required. This included Rieder triple-pane windows from Austria, a A.O Smith 80 gallon heat-pump water heater and to airseal this Brownstone a selection of tapes and membranes by Pro Clima

One of the hardest parts of making a NYC Brownstone a Passive House is not the level of insulation required, most of the time an R-21 or so wall will get the job done, but the airsealing of the front/back and party walls.

CONTEGA FC fleece tape taped to joist

Gennaro knew this well, especially that the corners of the building and the connections of the floor joist to the brick walls are sources of major airleaks and thus have to be dealt with. As sprayfoam and other sealants were out of the question, for both environmental (off gassing) and durability reasons (will crack and leak over time). The solution was to connect the party walls that would be covered/airsealed with a clay plaster to the joist with a felt tape. This 3-3/8″ wide tape, called CONTEGA FC  is adhered all the way around the joist before the clay application. The untaped fleece side is then embedded in the plaster, which assures a long term, durable and airtight connection between the plastered brick wall, and the airtight joist. This will allow the airtight layer to remain intact even if unlike materials moves/expand/contract slightly.

Plastered in CONTEGA FC, brick was coated with 2 layers of clay later to make it airtight

The first blowerdoor test, resulted in 3.0ACH50. A large amount of small leaks were found (basement, plumbing penetrations, etc.). The joist connections were performing well, however it was noted that the clay plaster leaked at certain spots and was too thin to perform as the proper airtight layer. After an additional layer of clay was applied, a couple more blowerdoors and the remaining holes were sealed – Gennaro reported an impressive blowerdoor flow rate of 300 CFM – which converts to 0.75ACH50 for this Brownstone – as far as we know the tightest house in Manhattan.

Congratulations to Ecobrooklyn crew with this fantastic result, the important work of sealing all the joist paid off!

INTELLO Plus under roof joist with service cavity – dense pack cellulose above

Products used:

INTELLO Plus under the roof joists, taped together UNITAPE and connected to plaster wall with CONTEGA FC.

TESCON Profil and UNITAPE at and around window boxes.

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