Page 123 - Zero Net Energy Case Study Homes-Volume 2

sis showed that the stacked units had a small exterior envelope area compared to a one- or two- level house and that it met the Passive House standard without the extra insulation.
Windows and doors are double-glazed products3 imported from Ireland and certified by the Pas- sive House Institute (PHI).
Building Envelope — Airtightness
The manufactured wall panels, thought sufficiently airtight with their internal construction, proved to be difficult to air seal when assembled together on site and joined to the site-built structural frame. Silicone gaskets were placed under the bottom plates and vertically between the pan- els. However, building and assembling prefabricated panels with the small tolerances that were specified proved to be challenging. Likewise, the concrete floor slabs were not sufficiently flat to prevent small gaps between the slabs and the bottom of the wall panels. With the weight of these panels approaching 11⁄2 tons, the placement task was difficult to execute.
Viscous liquid sealant eventually resolved these issues and the difficulty eased for the wall pan- els that were put into place at the upper floors as panel tolerances improved at the factory due to a quality control effort. The uniform flatness of the concrete slab was less of an issue at the higher floors also.
Smoke tests were done to pre-test the air sealing at each level and specifically to locate any of the possible gaps described above. Finally, the Blower Door Test at each individual floor dem- onstrated that the strict airtightness standard for Passive House certification had been achieved, namely less than 0.6 ACH50. The average value of each floor was 0.57 ACH50.
Heating, Ventilating and Cooling Systems
A ducted mini-split two-zone system provides primarily heating in each unit in this cool climate, though it has the capability of operating in a cooling mode for the rare periods of relatively high temperature. The tight air seal that was eventually achieved makes it necessary to have a con- trolled fresh air supply, so an ERV unit is designed into the system of each unit. Therefore, there are two systems of ducting air to each room, one for conditioned air and one for fresh air.
The kitchen exhaust fan directs air via a kitchen vent to the ERV and then to the outside. This maintains indoor air quality while still recovering heating or cooling energy from within the unit.
Lighting and Plug Loads; Control Systems
All LED lighting is used throughout the entire building. No motion detectors were installed for light shut-off. However, occupancy sensors are located in the bedrooms to reduce plug loads and eliminate “vampire” loads. One continuously electrical outlet not on the occupancy sensor is provided for phone charging.
Domestic Hot Water
The domestic hot water is supplied by a heat pump water heater4, which is separated into an outdoor equiipment component, the heat pump, and an indoor equipment component, the stor- age tank. This arrangement was selected so that the indoor enclosure would not be undesirably cooled.
3 Klearwall, https://klearwall.com/
4 The Sanden CO2 water heater, which uses CO2 as a refrigerant and has much less impact on the atmosphere than commonly-used refrigerants if the gas happens to leak from the equip- ment. https://www.sandenwaterheater.com/.
Zero Net Energy Case Study Homes: Volume 2
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SOL LUX ALPHA CASE STUDY NO. 11
(Following pp. 106-107)
View of roof deck and solar PV canopy.