A Brooklyn Co-op Seals Its Envelope – and Saves Big

The argument at Sun Garden Homes was airtight. Instead of simply patching water-damaged exterior walls, the board at the self-managed 70-unit cooperative in Brooklyn’s Sunset Park neighborhood decided to buy decades of moisture protection, energy savings, and interior comfort by swaddling the building in a blanket of insulation – “sealing the envelope.” 

“We could turn a crisis – cracking bricks and tenants getting wet and cold – into an opportunity,” says shareholder and building manager McGowan Southworth, volunteer project manager and an environmental consultant. 

The approach is central to the passive-construction movement. “Recladding” three exterior walls with powerful insulation will outlast brick re-pointing, which needs to be redone every 20 years or so. And this one-time fix costs about the same as a single re-pointing project: $1 million. 

“If you want to stay warm, you don’t eat a sweater, you put it on,” says project architect Chris Benedict, an internationally known sustainability expert. “And in passive building, ‘putting it on’ means balancing airtightness, ventilation, insulation, and windows to manage light, heat, air, water, and vapor.” 

Seven years ago, the 96-year-old building saved money and energy with a rooftop solar panel installation spearheaded by Southworth and Benedict. And the historic self-managed cooperative, established by Finnish immigrants, was now ready for the reclad challenge. 

In September, scaffolding was erected at the  three most vulnerable exterior walls, skipping the less-affected front and courtyard walls. Then, workers inspected, repaired, and prepared bricks for the first coat of a liquid membrane that promotes water drainage and is vapor-permeable. Called Sto Gold Coat, this first step alone – just completed in December – promises a 10 percent reduction in energy load.  

While a second, touch-up coat is on hold for winter, the consensus-driven board is tackling other issues, including whether and how energy-saving windows should be folded into the reclad. 

“Finalizing the choice has been the toughest, most contentious part of this process,” admits board president Mike Weiss. Windows will add about $400,000 to the current $600,000 bill for the insulation. But numbers are still fluid. “We’ve gone slowly because we’re still raising funds in-house and budgeting,” says Southworth.  

The board believes that the amount, though daunting, is doable. By combining the $30,000 in annual solar energy and submetering savings that contributes to a “sizeable” capital improvement fund with money from an ongoing special assessment and various grants and loans, Southworth is working to ensure that expenses won’t exceed the estimate for a re-pointing project.  

Since Benedict says that high-quality windows are essential to optimum sealing, homeowners are likely to reach a window decision soon. Once windows are installed, the serious business of exterior insulation will ramp up. First, four-inch-thick layers of heat-conserving mineral wool or foam will be secured to the exterior walls. Then, an outer shell of synthetic stucco will serve as a final sealant that can be customized to match the building’s exterior. The timing, final costs, and contractors for the last few steps are still being debated, although StoGuard products will probably be used throughout. 

If all goes well, the project will wrap by next fall, just in time to deliver cozy – and dry – apartments for winter. Then the Sun Gardens shareholders, with Benedict and Southworth as their guides, with continue their sustainability journey. “The building has already lasted almost 100 years and created enormous value for us,” says Southworth. “We want to set it up for the next 100 years.” 

PRINCIPAL PLAYERS – ARCHITECT: Chris Benedict. CONTRACTOR: Titan Contracting. MANUFACTURER: StoGuard.