A high-performing building should be evaluated by more than its energy use. Although energy efficiency is important, a building must also provide healthy air, thermal comfort, and protection from indoor environmental risks. Indoor environmental quality (IEQ) directly affects occupant health, comfort, productivity, and satisfaction. For HVAC professionals, this requires balancing energy performance with ventilation, filtration, humidity control, air distribution, and system reliability.
Indoor air quality begins with proper ventilation, but it involves more than simply bringing outdoor air into a building. ANSI/ASHRAE Standard 62.1-2025 establishes minimum ventilation rates and other requirements intended to provide acceptable indoor air quality and minimize adverse health effects. The standard addresses ventilation systems, filtration, air cleaning, controls, and building operation and maintenance (ASHRAE, 2025). It also includes updated guidance related to humidity control, demand-controlled ventilation, exhaust airflow, and filter efficiency (ASHRAE, 2025).
Effective IAQ design requires engineers to identify contaminant sources and determine how pollutants will be removed or diluted. This may involve outdoor-air ventilation, local exhaust systems, higher-efficiency filters, air-cleaning technologies, and proper maintenance. For example, a restroom, laboratory, or commercial kitchen may require dedicated exhaust to prevent contaminants from spreading to adjacent spaces. In addition, ventilation systems must be commissioned and maintained so that their performance does not decline after occupancy.
Ventilation alone cannot guarantee a comfortable indoor environment. ANSI/ASHRAE Standard 55-2023 evaluates thermal comfort using environmental factors such as air temperature, radiant temperature, humidity, and air speed, as well as personal factors including clothing and activity level (ASHRAE, 2023).
The standard recognizes that occupants may experience spaces differently even when the thermostat displays the intended temperature.
Consequently, HVAC design should consider the building envelope, solar heat gain, insulation, glazing, air distribution, humidity control, and occupant loads. Poorly placed diffusers can create drafts, while excessive radiant heat from windows can cause discomfort even when the air temperature is acceptable. A successful system must therefore provide reasonably uniform conditions while allowing appropriate local control when possible.
IEQ design also has an important role in reducing exposure to airborne infectious particles. ANSI/ASHRAE Standard 241-2023, Control of Infectious Aerosols, establishes requirements for reducing exposure through ventilation, filtration, and air-cleaning systems (ASHRAE, 2023). Rather than relying on one technology, the standard uses the concept of equivalent clean airflow. This approach allows a building to combine outdoor air, filtration, and air cleaning to achieve a desired level of protection.
For instance, a building may increase outdoor-air ventilation when conditions permit, use higher-efficiency filters, or operate portable air cleaners during an infection risk management mode. These strategies must be properly designed, installed, commissioned, operated, and maintained to be effective. Standard 241 also builds on compliance with applicable ventilation standards, emphasizing that infection-risk strategies should supplement, not replace, basic IAQ requirements (ASHRAE, 2023).
Together, ASHRAE Standards 62.1, 55, and 241 demonstrate that building performance is multidimensional. Energy efficiency, indoor air quality, thermal comfort, and resilience should be considered together rather than treated as separate goals. An efficient HVAC system that provides poor ventilation or uncomfortable conditions is not truly high-performing.
For HVAC professionals, the design process should continue beyond equipment selection and energy modeling. Engineers must consider how systems will perform during normal operation,
changing occupancy, extreme weather, and periods of increased health risk. By applying recognized standards thoughtfully and adapting them to local conditions, the industry can create buildings that use energy responsibly while supporting healthier, more comfortable, and more resilient indoor environments.
ASHRAE. (2023). ANSI/ASHRAE Standard 55-2023: Thermal environmental conditions for human occupancy. https://www.ashrae.org/technical-resources/bookstore/standard-55-thermal-environmental-conditions-for-human-occupancy
ASHRAE. (2023). ANSI/ASHRAE Standard 241-2023: Control of infectious aerosols. https://www.ashrae.org/about/news/2023/ashrae-publishes-standard-241-control-of-infectious-aerosols
ASHRAE. (2025). ANSI/ASHRAE Standard 62.1-2025: Ventilation and acceptable indoor air quality. https://www.ashrae.org/technical-resources/bookstore/standards-62-1-62-2
The ASHRAE descriptions confirm that Standard 62.1-2025 covers ventilation, filtration, controls, air cleaning, and operations; Standard 55-2023 addresses environmental and personal factors affecting thermal comfort; and Standard 241 uses equivalent clean airflow to combine ventilation and air-cleaning strategies.
