Sawkill Townhouse

Gut rehab to EnerPhit Standard
158 Clifton Place, Brooklyn

This house is a jewel cut from reclaimed wood: its owner runs Sawkill.  Luckily for us, he also has the Passive House bug. 

Paul Castrucci Architect and Blueline Construction led the team.  Right Environments provided Passive House consulting, enclosure detail consulting, mechanical and domestic water design, and quality assurance on all items above.

Low energy design typically relies on winter solar heat gain.  The rear facade faces south and takes shade from irregular obstructions.  Fish eye surveys helped determine how large and well-shaded the windows should be for best winter gain without overheating.  More specifically, we used floor-by-floor surveys as inputs into a calculation of winter shading factors for PHPP.  The surveys also served to evaluate the output of the planned rooftop PV system.

The diagram is from SunPath, which I wrote for the San Francisco PG&E Energy Center years ago.  It generates a diagram for any latitude and fish eye lens projection. The shading factors were calculated using the Solar Radiation Calculator, also from PG&E.  They can send you free copies.

The enclosure assemblies on this project are first class.  The house is heavy timber, built 1880.  The frame walls were originally infilled with brick, which we replaced with dense pack cellulose, using Pro Clima Intello as netting and vapor control layer.  A Solitex weather barrier covers the existing sheathing, then 3" rigid mineral wool, then a vented rain screen. The owner selected reclaimed Douglas Fir for the front cladding, applying the Japanese Shou Sugi Ban flame treating process to make it suitable for exterior use (see starting image).  The rear is wooden slat cut from the Coney Island boardwalk.

The grade-level masonry walls are insulated with EIFS and mineral wool batt, and the roof is dense pack cellulose with 4" polyiso above the deck.

Image courtesy Paul Castrucci Architect

Air barrier detailing is tricky, and ordinary drawing conventions don't always suffice.  Here we needed some air sealing work to happen before the floor joists were sistered; otherwise the sisters would block the sealing work from happening, and we'd have a leak that can't be economically sealed.  This drawing worked.  There were a couple of areas where a sister was pocketed for structural reasons, and we had small leaks there where the sister adjoins the existing, but otherwise the joist penetrations were real tight.  Note that the air barrier is drawn in red, and that's how the drawings showed up on site.  It's not easy to do, but it's worth it.  All the older and wiser folks say so.

We recently passed blower door test to EN 13829 Standard: 0.98 ach50.

Detail drawing courtesy Paul Castrucci Architect

There are two stand-alone split systems – one for the garden-level rental and the other for the triplex owner's apartment.  A slim-ducted 9 MBH unit heats and cools each floor.  PH newcomers, you read that right.  The heating and cooling system for this 2,900 sf house has 45 MBH of nominal capacity, and 27 MBH of heating capacity at NYC design conditions.  Compare that to the neighbor's 175 MBH boiler.  Is a forced-air system noisy, drafty, throat-drying, smelling of burned dust?  Not this one.

A single Zehnder CA550 ERV ventilates the whole house.  A pair of 4" ducts serves the garden apartment.  It's usually best to keep ventilation completely separated from heating and cooling, if budget and space permit.  That's how we did it here, but for each room we put terminated both ducts behind a single grill for visual cleanliness.  The heating/cooling duct has an opposed-blade damper and the ventilation duct a proprietary damper from Zehnder. 

Note that we built return air transfers everywhere.  This is a big deal, and it's often overlooked.  If the air can't easily find its way back to the return, the room will become pressurized, driving infiltration, and the flow balance will be disrupted, aggravating thermal control and air quality.  I measure it; it's real.  The good news is that with low-load buildings the transfers can be really small; sometimes a 3/4" door undercut is enough.

Lots more cool details can be found at the owner's blog here.