A heat-recovery ventilator (HRV) brings in fresh air from outside and exhausts inside air over a heat exchanger. It features a carbon-dioxide sensor to ensure it operates at the optimal levels—30 to 300 plus CFM, depending on occupancy.
The entire office space is heated and cooled by a single high-performance ductless mini-split head.
A heat-pump water heater, which is fairly new to the marketplace, pulls heat from inside the building for domestic hot water. Although the equipment has its drawbacks in a heating climate, Hagerman says it has performed well so far. “One of challenges with an office space is that during the summer it is producing more heat than it needs,” he says. “The heat generated by lighting and eight or nine people and their computers, printers and server adds up, especially in a super-insulated and airtight building. With the heat-pump water heater, we are able to use this excess heat to efficiently produce hot water with the added benefit of cooling down the office space. But the opposite will happen during winter, so we will be monitoring performance as the temperatures outside start to drop and switching the water heater to resistance-only heating mode.”
Hagerman says the project came in at just $15 more per square foot and took about three weeks longer than a typical retrofit project of its size. “The additional time was due to installation of the interior air barrier to satisfy the airtightness requirement,” he explains. “Some other unique requirements, like some additional roof framing to accommodate the insulation strategy, also took a bit longer than normal.”
Hammer & Hand monitors every Passive House it builds. Glasswood’s HRV and domestic-hot-water performance are being monitored with temperature sensors and flow meters. Indoor air quality and temperatures are also being logged. Every electrical circuit is independently monitored for energy consumption. This is important in a plug-load-heavy office environment. The monitoring system currently has been operating for six weeks.
Move In
The six members of Hammer & Hand’s home performance and building science division have been in their new office space for about three months. Hagerman, who thinks we often take our workspaces for granted, says his staff and visitors comment about how comfortable the Passive House space is.