Despite Maine’s rustic image in the outside world, the state is dotted with beautiful, historic red-brick downtowns, islands of urbanism in a predominantly rural landscape. Dating mostly from the 19th century, the buildings that make up these commercial districts have proven as sturdy and adaptable as they are charming. They’re also, generally speaking, energy hogs, a condition that’s much trickier to rectify than it is in newer, freestanding structures. So we are excited to be working on this fine 1870s building in downtown Gardiner, Maine. Following its owners’ vision of an energy-efficient, micro-urban pied-à-terre, we’ve undertaken a full renovation that includes restoring the building’s historic façade, inserting a cool, classico-modern interior, and upgrading energy performance and indoor air quality to Passive House levels.
As we found it, the building’s formal street elevation was largely intact, marred only by a folksy-suburban late-20th century storefront. Project architect Riley Pratt’s design reverses the damage, returning the building’s façade nearly to its original form. Inside, the ground floor will remain commercial space; the owners’ apartment and guest quarters will occupy the second and third floors, accessed by an expanded street-front vestibule and stair. The residential interior will interweave neoclassical themes with 21st century modernism in spaces that might feel at home overlooking the Seine rather than the Kennebec River. But the big excitement around here at the moment is the system of building-shell and systems upgrades we developed to bring this steam age building into the 21st century.
GO Logic’s preferred system of Passive House construction relies on wrapping an unbroken layer of exterior insulation around the building structure and thoroughly air-sealing the building envelope. This building’s historic façade, and the side walls it shares with its immediate neighbors, made continuous exterior insulation impossible, says construction principal Alan Gibson. Turning our normal approach inside-out, Alan and Riley devised a building envelope that locates virtually all of the insulation inboard of the masonry structural shell. “Here,” Alan says, “it all happens on the inside.”
After our crew gutted the interior of the building, mason Edward Small of Sheridan Brick & Stone Work sealed the brick walls from the inside with traditional lime plaster. We carefully closed air gaps also where the timber-framed floors and roof intersect with the outside walls. To the inside surface of this nearly airtight shell we applied 1-1/4 inches of rigid mineral wool insulation, followed by a 2×6 stud wall filled with dense-pack cellulose insulation, a high-tech vapor-retarding film, and gypsum wall board. The attic level will be used for storage, so rather than insulate the attic floor, we built out the existing roof structure to accommodate 18 inches of cellulose insulation, protected by a vapor retarder continuous with that at the walls.
Much to its credit, the local historic district approved the triple-glazed, tilt-turn German windows that are our first choice for Passive House projects, requiring only that we specify muntin bars to simulate the building’s original double-hung windows. The living spaces will be heated and cooled by efficient electric heat pump units. An existing oil boiler will heat the first floor, Alan says, “but the energy load’s going to be pretty tiny for the square footage they’re going to have.” The entire building will be served by centralized heat-recovery ventilation units, which will provide a continuous supply of filtered, tempered outdoor air.
All of that may sound like inside baseball for energy geeks, but our work on this project has exciting implications that extend far beyond Gardiner, and even Maine. “Brick is notoriously hard to retrofit for Passive House performance,” Riley says. “It takes a complete internal solution.” Developing a systematic approach to upgrading older urban structures while maintaining their historical integrity represents a win for established downtowns everywhere. “If we can do this,” Riley says, “it means there’s a way that older cities can move into the next century.”
