VRF/PASSIVE HOUSE CASE STUDY

Project: Distillery North Apartments
Location: Boston, Massachusetts
Owner/Developer: Second Street Associates, LLC, Boston, Massachusetts
Architect: ICON Architecture, Boston, Massachusetts
HVAC Engineer: Petersen Engineering, Portsmouth, New Hampshire
HVAC Contractor: Mechanical Air of N.E., Inc., Greenland, New Hampshire

The Project: The Distillery North Apartments (The Distillery North), located in South Boston, embodies the values of the local community: arts, culture, and sustainable living. The 28-unit complex follows the Passive House model, a building standard aimed at true energy efficiency, comfort, and affordability.

In 1984, Fred Gordon, principal owner of Second Street Associates, LLC, Boston, bought an old, 100,000-square-foot rum distillery originally owned and operated by Felton Rum. Five generations of the Felton Family made distilled rum in New England for 150 years. “I just fell in love with it,” said Gordon of the warehouse. “It was a building that nobody wanted, in a part of the city that nobody wanted to be in and I, in certain ways, predicted that the whole thing would turn around.”

Fast-forward to the mid-1990s, Gordon was determined to use the space to contribute to the environmental movement. He bought the rest of the city block and in 2009 decided to build a multifamily Passive House on the distillery property. As the low-energy building movement was relatively new at that time, Gordon expended significant effort researching energy-efficient systems. “The Passive House movement involves a huge amount of discussion about products,” noted Gordon. “If you went to the conferences both in Germany and in the U.S., which I did, there was all this buzz about air -source heat pumps. Air -source heat pumps were a revolution in terms of technology, energy efficiency and cost.”

The Challenge: Richard O’Dwyer, consulting principal, ICON Architecture, Boston, was one of the architects brought on early to The Distillery North team. He explained that product research and selection was a collaborative effort. “We were excited by the prospect of developing a project that would be intensely energy-efficient with a very low carbon footprint, that would deliver very clean air to breathe.” The owner also brought in a Passive House architect from Germany who had extensive experience with the constructability of larger Passive House projects plus local professionals who were familiar with smaller Passive House structures to assist in the process.”

The Solution: Targeting energy reductions of at least 60%, Gordon and his team had to tackle two issues to attain Passive House status: cut energy loads down as much as possible and use green power to assist in covering those loads. The Passive House Standard developed by the Passive House Institute also has strict benchmarks surrounding cooling and heating, requiring the building to have controlled mechanical ventilation with heat recovery (MVHR). After 100 photovoltaic solar panels were selected to help bring in green energy, Gordon knew a highly efficient HVAC system with air-source heat pumps and heat exchangers that could perform MVHR functions was needed.

Sarah Carter, project manager, Petersen Engineering, Portsmouth, New Hampshire, was one of the engineers who helped specify the ductless HVAC system for The Distillery North. She said, “The loads are greatly reduced in [a Passive House] type of building so there needs to be equipment that’s available in small capacities. A lot of equipment’s preset sizes would all be considerably oversized in a Passive House building, especially if they are for one- and two-bedroom apartments.”

The Test: With this in mind, Gordon decided to create a trial period for all the equipment in the rum distillery before breaking ground on the multifamily complex. “We took a tenth of the existing building and retrofitted that with all of the equipment,” he explained. “We had about four years’ experience with all of the [HVAC] equipment before we made a commitment to a really major construction.” The engineers determined that the air-source heat pumps were an ideal choice for a multifamily Passive House because each unit only uses the exact amount of energy required to cool or heat a space. Zoning allows for optimum occupant comfort, with substantial energy savings for the building owner.

The Results: The Distillery North Apartments have been open for tenancy since April 2017. Gordon and his wife, who actually live in the building, have been quite pleased with the first round of energy performance figures. Between the solar panels, positioning of the complex and an energy-efficient HVAC system, Gordon and his colleagues at Second Street Associates believe the utility savings are a real perk for residents. “For heating and cooling, we’re talking $65 per unit, per year - that’s less than a cappuccino from Starbucks,” said Gordon.

O’Dwyer also believes The Distillery North has been a success from both an energy conservation and an aesthetic standpoint. Throughout the course of the project, the team found that some developers in the field were worried that the strict building envelope and efficiency standards of the Passive House guidelines would impact curb appeal. “I think we’ve demonstrated with The Distillery North that we have a very contemporary building that ties in very nicely with the existing distillery building, which dates back to the 19th century,” O’Dwyer said. “Although incorporating the constraints of the Passive House model into the project was a challenge, with the right concept and a thoughtful design process those constraints ultimately enhanced the aesthetics of the final product.”

After years of collaboration with multiple green energy professionals, and the energy savings to back it up, Gordon has finally brought his Passive House to fruition. He noted, “Passive House is a very high bar, but we have way exceeded it. This building is something of a miracle.”

The Future: With the Passive House movement growing in popularity, Gordon is already developing another low-energy building on the property. This will add 37 apartment residences, six commercial spaces, an indoor theater, a grocery store, and a 2,600-square-foot greenhouse.