The growing family required slightly more space than the brownstone's original plan provided. Fortunately, local zoning regulations permitted the architects to add an additional story to the building. The new penthouse added enough space to include an art studio for the husband in the building's basement.
The top-floor master bedroom is defined by the new roof's bold angles, sloping twenty-one degrees and oriented along the north-south axis. This tilted and turned roof was designed to maximize exposure to the light and heat of the sun for solar thermal and photovoltaic collectors.
A penthouse mechanical room holds an HRV unit, located in the house's top story to provide cleaner air than would be available at street level and to ensure that the air intake and exhaust ducts to the exterior are kept short.
The white acrylic roof is finished with an eco-friendly surfacing material that reflects the sun but does not add contaminates to the rainwater-collection barrels used for irrigating the garden and plants on the roof terrace and in the rear yard.
After a lengthy investigation into the best method to insulate the existing front facade, Fabrica 718 decided to apply a layer of exterior insulation and finishing system (EIFS). Because of the extreme temperature differential in New York City, insulating the building from the inside alone can cause a freeze/thaw condition that could harm the masonry wall.
This fear was validated during a winter without occupants — one of the original brick walls cracked because of what looked to be freeze-thaw damage; the existing brownstone facing would be spalling and degraded.
Once construction started, it became evident that it would be better to remove the four inch face veneer and apply the EIFS, which is similar in appearance to brownstone but more affordable, to the existing masonry.
This would not only cut costs but also keep the finish in the same plane with the neighboring building. Most of the threewythe masonry wall remained in good shape, but areas below the windowsills had to be restored with concrete masonry units (CMU), as the deteriorated stone sills had to be removed.
The building's original wood cornice was replaced with a low-maintenance fiberglass replica, which was installed over the EIFS, allowing for a continuous thermal envelope.
On the rear facade, a rainscreen features an air barrier, four inches of rigid mineral wool insulation, and a thermally isolated framing system clad with cement panels, which are durable and low maintenance.
Providing both insulation and character to the building, the custom rainscreen panels range in height across the facade to align with window openings and play on typical wood-siding houses often seen in old Brooklyn.
Sealing the Brownstone
The double-height art studio in the basement has a concrete slab that required intricate detailing to meet Passive House standards and satisfy structural and waterproofing requirements. Any penetration through the building's superenvelope could throw off its airtightness, and a failure to stop thermal bridging at the perimeter cellar slab would mean significant heat loss.
Fabrica 718 collaborated with structural, geotechnical, and Passive House consultant ZeroEnergy Design and decided to line the bottom and the perimeters of the slab with two inches of XPS insulation.
A gravel bed and perforated pipe drainage system underneath the slab leads to a sump pump, and a polyethylene membrane just below the slab prevents ground moisture from migrating into the interior space.
Since air sealing of existing stairs can be difficult in retrofit projects, the architects designed new stair openings at each level of the house—the art studio in the basement, a guestroom at the garden level, an open parlor floor for entertaining, a second floor with a home office and children's bedroom, and the master bedroom penthouse and roof terrace.
The new staircases allowed the contractor to efficiently air seal the walls before reinstalling the stairs. In addition, the five sets of stairs became a unifying feature in the house, with their visually exciting but cost effective design.
The plate-steel stringers and perforated stainless-steel treads add special character to the home. The durable and low-maintenance material does not require a finish coat, and the stairs' perforated pattern provides a strong graphic element while bringing natural light to the center of the row house. The stairs are bound by clear glass and, along one wall, a simple handrail that houses LED ribbon lights controlled by eco-timers.
Lighting and Finishes
After implementing techniques to maximize daylight at the stairwells, Fabrica 718 worked with the clients on a lighting strategy for the rest of the house based on using LED and fluorescent lights limited to five types of fixtures. The challenge was to create gallery-like lighting conditions for the couple's art collection and the studio. The owners eventually opted to install low-cost down lights and track lighting fixtures with the highest-quality retrofit LED bulbs available.
The clients' minimalist aesthetic kept the project unadorned, contributing to the architects' overall goals of energy efficiency and simplicity. Reclaimed materials were used for the industrial flooring on all levels as well as in specific areas of the house, including the parlor space, where a wythe of reclaimed brick was added to coincide with the ceiling opening.
This brick was salvaged from the two fireplace flues that were demolished on-site. Custom designs by Brooklyn fabricators include the stainless steel LED strip lights at the top of each stair landing, which are practical, made locally, and add character to the space.
Julie Torres Moskovitz is an architect and principle of Brooklyn, New York-based Fabrica 718, a collaborative design firm focused on reinventing urban space. She is a graduate of the University of Pennsylvania Master of Architecture program (2000), and teaches graduate design studios at the Pratt Institute. Julie is LEED certified and is a Certified Passive House Tradesman.
A hardboard rainscreen treatment finishes a new concrete-block rear facade of the Tighthouse. The rainscreen system is detailed with a vapor-permeable air and water barrier, mineral wool insulation, and a thermally isolated furring channel system. Photo: Hai ZhangExtra Large Image
The main stair of the Tighthouse runs along one edge of the living space, leading from the entrance to second-floor spaces, including a home office. The handrails are outfitted with hidden LED strip lighting. Photo: Hai ZhangExtra Large Image