Step 3 Home in Maple Ridge
The four-bedroom 2600 sq.ft single-family home with unfinished basement is a typical spec home for this Maple Ridge neighbourhood. Corey already had the completed design when he started working with Energy Advisor, Donald Taylor from DW Energy Advisors. It is ideal to engage an Energy Advisor as early in the process as possible, as making minor changes to the design can be a cost effective way of improving energy performance.
The first step of building with the Energy Step Code is engaging an Energy Advisor. The Energy Advisor models the building design to see how it will perform, and will suggest different ways of boosting energy performance.
Corey Siemens of Fernwood Developments specializes in both high-end custom and affordable single-family residences.
• Heating needs – measured in Thermal Energy Demand Intensity (TEDI). This is how a measure of how energy efficient the building envelope is.
• Mechanical efficiency – measured in Mechanical Energy Use Intensity (MEUI) OR with the EnerGuide Rating System (% lower than reference house, which is the same house built to code minimum)
• Airtightness – measured in Air Changes Per Hour (ACH) at 50 Pa.
There are many ways to meet the targets, so each builder can work with an Energy Advisor to decide what works best, and what is most cost effective, for their building. Learn more about the diverse range of energy efficient building techniques and materials in the BC Energy Step Code Builder Guide published by BC Housing.
Here is what worked for Corey:
Envelope EfficiencyCorey worked with the Energy Advisor before he started construction to determine what upgrades to the envelope were needed to meet the Step Code metrics. Everything he chose to do uses readily available building materials and techniques.
Walls: The walls have R22 batt insulation. Corey considered moving to 2x8 framing for the walls to make room for more insulation, but the energy model showed that he could achieve the target with standard 2x6 construction. Likely in order to meet the updated metrics, he would have needed either 2x8 framing or a layer of insulation on the exterior of the walls.
Attic: Boosting the attic insulation to from R40 to R51 was a simple and cost effective way to improve the thermal performance of the attic. The house has a steep roof pitch, so it was unnecessary to make changes to the design.
Basement: The Building Code only requires under-slab insulation at the perimeter; however, insulating under the entire slab with EPS foam was cost effective because there were savings from needing less sand. This feature will lead to a more comfortable basement if future homeowners choose to finish it.Windows and Doors: The windows were slightly more energy efficient than base code requires and have plastic spacers to reduce thermal bridging.
Mechanical Efficiency A Step 3 home does not require expensive or complex mechanical systems. By first focusing on an energy efficient building envelope, it’s possible to install a smaller heating system. The energy model showed that Corey could meet the targets by boosting the efficiency of the furnace and choosing a tankless hot water heater.
Space Heating: The natural gas furnace is more efficient than what the Building Code requires and has a variable speed drive. Future homeowners can choose to install an air-source heat pump if they desire, and keep the furnace as the air handler and backup heat source.
Water Heating: Corey chose to install a tankless, “on-demand” natural gas hot water heater. This system boosts the mechanical efficiency of the home because it does not use energy to continuously heat water in a storage tank. As an added bonus, this system saves space in the mechanical room and is a high demand feature for prospective homebuyers. This house is also solar-ready, meaning the conduits are installed for future solar-thermal panels leading from the roof to the mechanical room.
Ventilation: Balanced and continuous ventilation is a requirement, especially with more airtight homes. Corey considered a heat recovery ventilator (HRV), which would preheat incoming fresh air, but in the end opted for balanced ventilation using the furnace and bathroom exhaust fans.
Because this home meets Step 3 and uses natural gas for space and water heating, Corey is eligible for a FortisBC home performance rebate totalling $2500.
AirtightnessThere are several methods of installing a continuous air barrier. Typically, Corey uses poly on the inside, which acts as both the vapour retarder and air barrier. For this project, Corey opted to try something new and used the exterior sheathing membrane as the primary air barrier.
Exterior Air Barrier: Choosing do use exterior sheathing membrane as the primary air barrier has several benefits, including fewer penetrations, and lower likelihood of damage in the future. Since the air barrier must be continuous, this technique requires sealing the joints and interfaces with sheathing tape and liquid sealant. This method required Corey to think ahead and communicate with the framers. The house wrap had to be brought in behind skirt roofs before framing them, as well as at the top plate to connect with the poly forming the air barrier on the ceiling.
The air barrier is more than just the primary air barrier material (in this case, sheathing membrane). It also consists of windows and doors, tape, poly on the ceiling, caulking, gaskets, and other components to create a continuous air barrier. All the trades interact with, and are responsible for ensuring a continuous air barrier.
Mid-Construction Airtightness Test: While the first two Step Code metrics (envelope and mechanical efficiency) can be modelled by the Energy Advisor, the airtightness metric can only be measured once the house is built. In order to ensure the final house met the target, Corey had the Energy Advisor coming pre-drywall for a mid-construction airtightness test. This is strongly encouraged, since airtightness can still be improved at this stage.
The continuous air barrier consists primarily of the sealed sheathing membrane, but it connects with other components at different places.
Corey and the framer had to think ahead to ensure the air barrier will connect from the exterior to the interior at the second storey ceiling where the air barrier is poly.
The siding installer becomes an air barrier installer. The sheathing membrane was caulked to the foundation to ensure a continuous seal.
A mid-construction airtightness test ensured that leakage areas are spotted and fixed, and gave Corey confidence he will meet the target at the final airtightness test.
Many Energy Advisors use thermal imaging during the airtightness test to identify leakage areas.
- Energy Advisors are the key to success
- Plan ahead
- Conduct a mid-construction airtightness test
- It’s a team effort
When it comes to the Energy Step Code, an Energy Advisor is the Builder’s best friend (and valuable resource!)