In 2016, an abandoned youth care building in Hebron, Nova Scotia, a small community on the outskirts of Yarmouth, was acquired with the intent to retrofit and repurpose as affordable housing, primarily geared towards senior residents. The nine-unit building was retrofitted to Passive House standards as part of the Investment in Affordable Housing program to implement high energy performance design in new and existing properties.
The goal of this project was to reach the PHIUS+ 2015 standard, which has slightly different requirements than the typical Passive House criteria. PHIUS is a distinctly different organization from the Passive House Institute; it is US-based and has worked to shape its database and requirements to the North American market and climate. One of the criticisms that some designers have about the Passive House Institute is that it can be too Eurocentric, having been founded and developed in Germany. For this reason, many professionals looking to get certified as Passive House designers seek training through PHIUS instead of, or in addition to, the Passive House Institute.
The entire building was stripped to its framing and passive elements were integrated. The building’s insulation values were substantially increased in the ceiling, walls and the slab measuring R-values of R103, R63 and R27, respectively. The average u-value of the windows measured in at 1.19 W/m2K, and the air change rate was measured to be 0.66 air changes per hour (ACH). It is important to note that this air change rate would not have met the Passive House Institute certification criteria, but, was acceptable for the PHIUS + 2015 standard.
In addition, the building has an air to water heat pump with a minimum COP* of 3.5 for primary heating plus a high efficiency, propane fired condensing boiler for backup. The building also has a high efficiency central ERV** system, built in Canada by Tempeff, which acts as the building’s lungs. An ERV not only recovers heat, but also factors in humidity making it the best choice for occupant comfort in a cold, humid climate. Tempeff’s ERV makes use of DualCore® technology allowing for continuous fresh air supply and frost-free operation in this climate.
Humidistat controls are installed with continuous exhaust fans in the kitchens and bathrooms to further increase occupant comfort. These two systems working together provide high indoor air quality, adequate heating, cooling as well as the ability to keep humidity levels within a comfortable range year-round. This project cut space heating needs by up to 85% compared to conventional building, costing approximately $30 per month to heat each unit.
There are six primary factors which make up the success of the project:
The building has considerable southern exposure and large windows, providing significant daylight to each unit; 95% of occupied floor area is within 7m of an operable window. Energy Star/DLC-certified LED fixtures and Energy Star rated LED lamps are used for additional lighting. Exterior fixtures are automatically operated via a dawndusk photocell. Projected annual energy consumption for lighting in the building is 3.21 kWh/m2.
Ventilation and dehumidification is provided via an ERV system as discussed above. The system meets and/ or exceeds NBC, ASHRAE, HRAI, and Health Canada guidelines and regulations.
The building was designed using locally available building materials and practices to achieve high energy performance objectives. Comfort and air quality are enhanced when buildings are built to such standards, including improvements to HVAC and materials that minimize noise. Furthermore, the site is located adjacent to Doctors Lake and provides plenty of outdoor space so occupants can enjoy the surrounding landscape. Simultaneously, the property retains access to services and gathering places like the Hebron Recreation Complex, local school, and restaurants, all within a 5km radius, allowing the residents to stay connected with their community.
All plumbing fixtures installed meet North American quality and conservation standards, resulting in approximately 20% less water used as compared to standard fixtures. Energy Star laundry equipment is installed to further limit consumption. This has led to a projected potable water consumption of 0.7 litres/m2/occupant/year.
Most of the construction materials used were locally sourced, reducing the carbon footprint. Less environmentally intensive insulation, such as blown cellulose and mineral wool, were also chosen to minimize the overall impact of the project.
Local materials and a southern orientation help ensure lower life cycle costs for this building. Also contributing to resource conservation are the exterior sensored lighting system, and the pumps and circulators that use Variable Frequency Drives. Similarly, Outside Air Temperature sensors optimize space and domestic hot water heating. Lastly, all appliances are Energy Star rated and all electricity consumption is monitored remotely. Cumulatively, these approaches and technologies are projected to minimize the project’s annual energy consumption to 47.41 kWh/m2. Rough-ins were also created to allow a minimum 18kW solar photovoltaic installation in the future. Such an addition could produce roughly 58% of the building’s total annual energy consumption.
Staff and occupants were provided training on what makes this building special from both design and user perspectives. Those who call this building home see firsthand how it works and can attest to the benefits over conventional design. The occupants belong to a small community, so this building and their experiences touch a lot of families directly and encourage efficiency elsewhere in their lives. The maintenance staff are also involved to discuss and reinforce these ideas, as well as share new information with occupants and community members.
Construction costs of this retrofit were compared to what would have been needed to comply with NBC standards. The Passive House approach was found to cost 6% more up front with an estimated returnon-investment of less than 10 years. This clearly documents the business case for Passive House construction and is being used to encourage more construction of this type in the future, for both new builds and renovations.
Remote monitoring of the electricity consumption is also being used to solidify long-term consumption estimates. With electricity rates and operations costs steadily increasing, Passive House provides a financially sensible and environmentally responsible option for moving forward.