Passive House Construction

Construction

The Fort St. John Passive House provides 2155 sqft of internal living space with 3 bedrooms, 2.5 bathrooms and 1 flex room. The house is designed to be universally accessible. Construction of the house broke ground in January 2013. The prefabricated thermal envelope panels were constructed in Williams Lake, BC and arrived onsite in March. The panels were erected in 10 days. Following this, the windows were installed and the thermal envelope was taped and sealed in the spring of 2013.

After this, the construction progress suffered from long delays, first due to the need to procure more funds from City Council; then due to heavy workloads of staff. The project also suffered from staff turnover and attrition, which is very typical in a northern community. Once the construction momentum fell off track, it was very difficult to convince busy sub-trades to complete the remaining work. The drywall was not completed until early spring of the following year.

Passive House certification was received from Passive House Institute US in June 2015.

Construction Challenges

In this Northern region of the province, access to building materials and products are limited, inflating costs. Additionally, because Fort St. John has a very busy very short construction season, recruiting qualified trades people was very challenging. Specifically finding those with expertise in working with prefabricated wall systems, air sealing, PV installation, transformer energy monitoring software and hardware, HRV and heat pumps was difficult. 

If we had to do this project again what would we do differently?

  • We would simplify the architecture. Second floor vaulted ceilings are visually appealing but led to increased crane costs. An insulated ceiling panel with a standard engineered truss system would be more cost  effective

  • We would also do a slab on grade foundation or a full tuck under garage under the house with an insulated basement ceiling pre-fab panel. Early in the project it was estimated that the engineering for a slab on grade foundation would exceed that of the option of a city-spec footing backfilled and insulated with a concrete floor. This was not the case. Excavation was substantially greater than expected.

  • Use the concrete floor as the finished floor. The extra finishing details adding hardwood flooring adds substantially cost and complexity for contractors. This would have also allowed for the slab to be heated (radiant in-floor heating), thus simplifying the mechanical system as well.  This may have also allowed for the integration of domestic hot water heating and in-floor heating in one system, with further potential to use a fan coil to preheat or post heat the HRV supply air.

  • Use an HRV with electric defrost. While the unit chosen was exceptionally efficient (which helped ensure certification was achieved) and does not require a defrost cycle (i.e. minimal auxiliary electricity consumed) it was more difficult to source, less compatible with off the shelf  user control switches, and was significantly larger in size.  The only caveat is that the additionally auxiliary electricity used for electric defrost may compromise certification (e.g. the primary energy requirement).

  • The City being the general contractor.  While the City became the contractor not out of choice but of necessity, it did prove to have its merits. This was invaluable for a first project due the intimate learning and control leading to increased project awareness, energy monitoring follow through, post occupancy evaluation and ultimately to ability to compile a case study.  But this also led to higher costs and a longer project time frame. So this was a good lesson for the first time out but not one that we would choose to repeat.

The Passive Details

The home’s energy efficient features include; a ultra-insulated building envelope reducing heating and cooling demand by 90%  a heat recovery ventilator with 90% heat recovery efficiency, a 99% reduction in greenhouse gas emissions (GHG’s), extreme air tightness, net-zero energy readiness, air conditioning, a uniform temperature throughout, metal roofing, a solar electric array, high efficiency tilt/turn opening windows, and energy monitoring equipment. More information on the specifications of the project can be found on the Marken Design Blog

In addition, the house was built to be universally accessible and complies with relevant portions of the Safer Home Standard. That means it is designed to accommodate the functional needs of everyone: children, adults and seniors with or without activity limitations or disabilities.

The mechanical system consists of a direct-ducted ventilation system with heat recovery ventilator (HRV) and a combination of electric resistance heating (baseboards for backup heat) and point source mini-split ductless air source heat pumps (i.e. air conditioning) for heating and cooling. Domestic hot water is provided by a hybrid electric heat pump. This system will consume about 90% less heating and cooling energy than a typical code built house due to an extremely energy efficient building envelope. The heating/cooling cost for the year is estimated to be $200-$400, which amounts to annual savings of approximately $1000-$1800 when compared to a house built to provincial building code standards in this climate. The house is net-zero energy ready, meaning that it is an ultra-efficient building that can be adapted to net-zero energy at a later date through implementation of renewable energy technologies on site. A 2.82kWp solar photovoltaic (PV) system installed on the roof will produce about 3500 kWhr/year (~25-30% of the homes total energy requirements). The remaining southern portion of the roof is pre-wired with electrical junction boxes for future PV expansion. Energy monitoring equipment is installed with an on-line analytics subscription for monitoring.

This home is 100% electric, utilizing provincial hydro-electric power. Using air-source heat pumps in the house with backup electric baseboards installed throughout, the house will emit 0.05 tonnes of GHGs per year — over a 99% reduction in tonnes of GHGs relative to a typical single-family detached dwelling. A single-family detached dwelling emits around 10 tonnes of CO2 per year, on average. An airtightness level of 0.33 Air Changes per Hour @ 50pa was achieved. By comparison, an average home built in the 2000s in Canada would be at 3-4 ACH@50pa.

Performance Ratings: Certification as a Passive House plus (PH+) was achieved through PHIUS. The house has also achieved an Energuide Rating of 91, is certifiable as LEED Platinum (should dual certification be sought) and is Net-zero Energy Ready.

Passive House Product List

Passipedia is an excellent resource for Passive certified products. 

The following is a list of sources for the Fort St. John Project. 

1.            Certified Passive House Triple Pane Wood Windows

2.            Prefabrication Wall and Roof Insulated Wood Panels

3.            Sealing Tapes for Airtightness control used on Wall and Roof Panels 

4.            Rock Wool Insulation

5.            Air to Water Heat Pump Hot Water Tank

6.            Heat Recovery Ventilation System

7.            Air-to-Air Heat Pump Space Heating System 

Questions or Comments?

Contact: Economic Development
Phone: 250.787.5787