Building a Step 5 Home
The BC Energy Step Code is the new standard for energy efficient construction in the province. Although Step 5 won’t be mandatory across the province until 2032, many homeowners are already striving to achieve Step 5 for the energy savings, rebate money, and environmental considerations. While there are many interacting factors that differ on every project, this post outlines some general guidelines and best practices. It does require some forethought and planning, but achieving Step 5 is within reach for every new build!
Simple Building Geometry. Every bump out, jog, and corner in a build can reduce the overall energy performance. The greater the surface area to volume ratio of a space is, the more chance there is for heat loss. Thermal bridging at corners from increased framing members also contributes to heat loss. As well, taller buildings are more prone to the stack effect, whereby warm air rises and leaves through the upper story ceiling and walls, pulling cold air in through the bottom of the building. Designing a building with simple geometry, reduced thermal bridging and reduced exterior elevation can help achieve a Step 5 project.
Highly Insulated Building Envelope. Step 5 buildings must go above and beyond the code minimums for insulation. They typically require at least R50 in ceilings, exterior insulation or double stud walls, insulation under the slab and well insulated foundation walls.
High Performance Windows. Triple glazed windows with low-e coatings and argon fill are necessary to achieve a Step 5 build. Windows are usually one of the greatest areas of heat loss through the building envelope . For code minimum windows, they are equivalent to a wall section of only R3 (whereas minimum for walls is R22). High performance windows pay themselves off in energy savings over the lifetime of the window, and also improve indoor comfort by reducing drafts and cold spots in your home.
Low Window to Wall Ratio. Reducing the number of windows overall, as well as orienting them strategically, greatly impact a buildings’ energy performance. Windows should be mainly oriented to the south and east, and minimized to the north, where the most heat loss occurs. A build with a high window-to-wall ratio may have a hard time achieving a Step 5 rating.
Airtight Building Envelope. To reach Step 5, an air leakage target of 1.0ACH or better must be achieved at the final blower door test. Detailing the air barrier is not challenging, but does require forethought, attention to detail, and communication with sub-trades about the importance of maintaining an intact air barrier. During the design phase, you should be able to draw a line representing the air barrier around the entire building to show how it will be detailed at junctions such as between floors, walls and ceilings, and around windows etc. A mid-construction blower door test before drywall goes up can help to identify leakage areas while they are still accessible and can be addressed.
Heat Recovery Ventilator/Energy Recovery Ventilator (HRV/ERV). The heat recovery aspect of these units helps overall performance by decreasing the heating needs of a building. A highly efficient HRV/ERV unit transfers heat from warm air leaving a house to the cooler incoming air.
Air Source Heat Pump (ASHP). Electricity is the most efficient fuel source for heating/cooling needs in British Columbia. An air source heat pump transfers heat from the outside air into your home, working the same way that a refrigerator does but in reverse. If baseboard heaters are 100% efficient (1 joule of energy is turned into 1 joule of heat), then ASHPs are 300% efficient or better (1 joule of energy turned into 3 joules of heat). They can also be operated in reverse, providing cooling to a home.
Heat Pump Water Heater: Using the same principles as the air source heat pump, a water heater heat pump draws heat from the surrounding air to heat water in a tank. It’s best to place these units in unconditioned space, like a garage, because they can increase space heating loads if they are using heat from air in conditioned spaces. Although they are more costly than a conventional tank, the savings in reduced energy use will pay itself off over the life of the system.
All these components come together to create a home that is durable, comfortable, low-cost to operate and has reduced operational carbon emissions. The best way to determine if you are on track for a Step 5 build is to work with an energy advisor to have all the components of your project modeled together. From there it is possible to determine which upgrades are the most cost-effective ways of reaching Step 5. Contact us if you are thinking of building a highly efficient, high performance Step 5 home !