Starting with an energy budget
To navigate the pursuit of this energy performance goal, especially against the onerous energy demands of the engineering laboratory, B+H and mcCallumSather upended the typical design process, rooting their design in the development of an innovative energy budgeting strategy to help prioritize energy demands. Similar to any other significant project mandate, such as schedule or capital budget, this energy budget is honoured as a strict guideline to ensure the significant challenges associated with net-zero performance are appropriately articulated, categorized, and overcome.
To inform this exercise, the design team studied energy use intensity (EUI) values for known high-performance buildings in Canada. The team concluded that an annual EUI target of 75 kWh/m² was not only desirable, but also achievable for the programming, which consists of primarily classrooms, teaching laboratories, and collaborative learning spaces. (In the United States, this equates to 24 kBtu/sf annually, and 0.27 GJ/m² annually for Canadian government types.)
Creating the high-level vision
From the outset, the team recognized two important strategies—building enclosure performance must be exceptional, and active building systems must be ultra-energy efficient.
The HVAC design is based on a dedicated outdoor air ventilation system (DOAS) with local heating and cooling. The high-performance enclosure will maximize passive design strategies and significantly reduce the amount of heating and cooling required for the building mechanical systems. The DOAS is crucial to the design, as this type of HVAC system eliminates simultaneously having to heat and cool spaces, thereby providing superior air quality as return air is not recirculated in the building, while maximizing the exhaust air heat recovery performance.
Concept design energy use breakdown
A high-level energy model was created to investigate where energy would be used in the building and the potential impact of different HVAC approaches on the amount of onsite renewable energy required to achieve the net-zero energy target. Three lessons were learned from this exercise.
1. The building process and receptacle loads would be the single largest energy end-use in the building at an estimated 20 ekWh/m² annually.
This emphasized understanding how the building will be operated and what equipment will be plugged into its receptacles are critical to determining required energy generation from the onsite renewable energy system.
2. The next two largest energy end-uses include space heating and lighting, immediately followed by pumps, fans, space cooling, and domestic hot water.
From a building design perspective, enclosure heat loss performance and the efficiency of heating systems are of critical importance, as is the lighting design. However, the remaining energy end-uses were all significant to the low-magnitude annual target of 75 ekWh/m²—all analysis required careful attention to detail in the design.
3. To achieve a high-performance building, all systems must be synergistic.
The enclosure design, DOAS ventilation system, and low-energy lighting design combine to allow for low-intensity, low-energy heating and cooling plants. All investigated options achieved below 25 ekWh/m² a year.
It was clear that heat-pump-based solutions used significantly less energy than fossil fuel solutions. The design team’s early analysis included understanding the difference between modern air-source variable flow heat pump solutions and variable flow ground-source heat pump solutions. The differences were minor, but warranted detailed evaluation—suitable for this level of building energy performance.