In today’s world, where energy costs continue to rise, the need for resilient, energy-efficient buildings has never been greater. Passive house design employs passive strategies, such as high-performance insulation, airtight enclosures, and reduction of thermal bridges, paired with highly efficient mechanical systems, to reduce energy use. While the term might suggest it is only suited for homes, there is potential for passive building strategies in many project types, particularly residence halls.
Across the country, universities are investing in essential upgrades to their campus buildings. As heating and cooling account for a large share of total energy use, residence halls have considerable load reduction potential via passive building strategies. Passive building strategies, such as airtight construction, efficient ventilation, and a well-insulated enclosure, target heating/cooling demand reduction and improve thermal comfort.
" }A rendering of Catawba College’s new residence hall, estimated to be completed by Fall 2026.
Stantec recently completed the design for Catawba College’s new residence hall and has been officially recognized as a Design Certified Phius CORE 2024 project, one of the primary passive house certification systems in the United States. This residence hall is the first in North Carolina to achieve this distinction. With the first of two steps completed for the Phius certification process, the final certification is expected to be finalized in the next few years, once the residence hall is fully operational. The building is designed to achieve an energy use intensity (EUI) of 29.7 kBtu/ft2yr, nearly a 50% reduction from typical residence halls across the United States. With 40% energy cost savings, compared to the North Carolina energy code, the project is expected to receive a $92,000 incentive and $19,000 in annual energy cost savings. The design team employed a data-driven, climate-responsive approach to reducing cooling demand in the warm, humid conditions of climate zone 3A.
Constructing residence halls to meet the rigorous Phius standard can be challenging, but the benefits make the effort worthwhile. Some of the hurdles the project team worked through are listed below:
- Higher occupant density: Residence halls have more people per square foot than a typical single-family home or apartment building. This results in increased plug loads and mechanical demand, intensifying building energy consumption. At Catawba, lighting and plug loads account for 59% of total energy consumption, considerably higher than in a typical multifamily or single-family building.
- Complex zoning: Due to a residence hall's density, it’s common design practice to zone multiple rooms to a single HVAC unit. At Catawba, each heat pump serves at least two rooms, requiring careful load balancing to help maintain the same level of comfort for everyone. In buildings with poor envelopes and a single HVAC unit serving multiple rooms, one occupant might feel uncomfortably cold while another feels fine, simply because their temperature preferences differ. At Catawba, the building envelope helps balance those conditions by stabilizing heating and cooling loads. This reduces the reliance on HVAC systems and the need for extreme temperature adjustments to maintain comfort across zones.
- Compartmentalization requirements: Under EPA Energy Star standards (required for Phius), every one- or two-bed student room opening into a corridor is considered a “dwelling unit” and must meet strict airtightness rules, reducing the common practice of undercut doors as a return-air strategy.
The primary objective from the outset for Catawba College's new residence hall is to make decisions that prioritize student well-being while aligning with Phius performance standards.
There are several benefits to investing in energy-saving building practices through passive building strategies. These benefits can support the building’s resilience, operations, and energy savings.
- Durability: Academic institutions want their buildings to last. Passive buildings are durable because they may help reduce moisture infiltration, air leakage, and mold; extend the lifespan of mechanical systems that operate less often and at lower capacity; and support energy efficiency that may align with future code requirements.
- Energy savings: Residence halls consume large amounts of energy due to occupancy density and 24/7 operation throughout the academic year. At Catawba, passive building strategies are projected to achieve approximately 50% energy savings compared to a typical residence hall.
- Indoor air quality: Indoor air quality in living spaces has become a growing priority in recent years. In residence halls where students live in close quarters and illnesses spread easily, maintaining clean indoor air is an important consideration. Catawba’s new residence hall leverages dedicated outside air systems that can lead to improved ventilation effectiveness, moisture control, and higher filtration, which may improve air quality and reduce mold risk.
- Thermal comfort: Thermal comfort is among the top criteria that impact students’ satisfaction with their residence hall. Passive buildings’ airtightness and thermal performance requirements help reduce drafts and cold spots, resulting in comfortable indoor conditions.
- Efficient form factor: An efficient form factor reduces exterior surface area and difficult geometry issues, allowing the enclosure to be easily air sealed and reducing heat transfer.
- Decreased demand on HVAC: In most buildings, heating and cooling are among the largest uses of energy. Using passive building strategies to decrease heating and cooling loads, less than 10% of Catawba’s new residence hall’s energy use is dedicated to heating and cooling combined, illustrating the energy savings associated with passive building strategies.
- Resilience: With the ever-increasing frequency of natural disasters, resilience plays an important role in maintaining operations and safety. Studies show Phius-certified buildings remain within comfortable temperatures far longer after power outages than other energy code buildings. Catawba students benefit from a building designed to remain safe and comfortable during outages or extreme weather.
Passive building offers a path to efficient and comfortable residence halls. As the next generation of students move into these buildings, it becomes clear that performance and comfort are not mutually exclusive and can complement one another. This design approach can help universities support their investments and create facilities designed for long-term use. Institutions may consider passive building strategies for future projects as interest in sustainable campus living continues to grow.
A version of this blog was originally published by Page, now Stantec.
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