by Scott Henriques and James Barron
What do you do with an historic, 1800s vintage, one-room schoolhouse experiencing destructive moisture infiltration on a small, sparsely populated island with a mostly solar microgrid? Why, mitigate the moisture and provide a modern, near-net zero HVAC system, of course.
Such is the case for an HVAC and moisture evaluation and assessment at the Cuttyhunk Island School in the town of Gosnold on Cuttyhunk Island, the last island in the Elizabeth Islands chain that extends southwest from Woods Hole. The only access to the island was by private boat or limited off-season ferry.
Weston & Sampson was retained to assess options to correct moisture infiltration issues and update the building’s aging HVAC system. The town’s goal was to not just alleviate these issues but to also make the building more energy efficient and sustainable. Since the island gets 70% of its energy needs from an on-island solar field, having an oil-fired furnace in the schoolhouse simply no longer fit in with the island’s sustainability efforts.
The concrete floor in the crawlspace under the often-used building, which has no floor drains, is plagued with wet areas and a series of settling cracks. Even with a dehumidifier running constantly, there is no ventilation for the mechanical equipment and the crawl space is often moist and humid.
The recommended solution for resolving the moisture buildup on the concrete floor involves installing a drainage mat that drains into an airtight sump pump, overlain by extruded polystyrene and a new concrete slab with moisture mitigation admixture. We also recommended adding a new air- and water-tight exterior bulkhead door and frame to minimize moisture and air entering the crawl space.
Additional mitigation measures include a new, high-efficiency, air source heat pump and energy recovery ventilator to replace the aging and inefficient oil furnace to provide heating, cooling and mechanical ventilation. Air source heat pumps are up to three times more energy efficient than oil furnaces, so the town should realize energy and carbon footprint savings very soon.
The HVAC and other upgrades to Cuttyhunk’s schoolhouse will bring it solidly into the 21st century. Not only will the building’s heating and ventilation issues be resolved economically and for the long term, but the building will also be useable year-round for meetings and other needs, which it hasn’t been for many years.
Scott Henriques, PE, LEED AP, CEM is a mechanical engineer and team leader, and James Barron is an architect and senior job captain at Weston & Sampson’s Foxborough, Mass. office. They can be reached at henriquess@wseinc.com and barronj@wseinc.com, respectively.
