Heating and Cooling, Sustainability/Business Continuity

The Importance of Achieving Optimal IEQ in Commercial Buildings with VRF Systems

The COVID-19 pandemic heightened awareness of how building systems operate and impact occupant wellness. The average person is reading articles, watching videos, engaging in social media exchanges, and asking pointed questions. They want to know what building owners and facility managers are doing to provide healthy spaces to live, learn, work, and visit. Smart buildings designed for occupant health and wellness are highly marketable and also offer improved comfort, efficiency, resilience, and sustainability.

Understanding IEQ

Indoor environmental quality (IEQ) describes how an indoor environment affects occupant health and wellness. Most people spend about 90% of their time indoors, so what they breathe, feel, and hear within the built environment has significant implications for their quality of life. Indoor air quality (IAQ) is the most well-known IEQ component, with clean, fresh air universally recognized as a prerequisite for health. By necessity, IEQ is more comprehensive than IAQ alone.

The Relationship Between IEQ and Sustainability

Optimal IEQ and sustainability are interrelated. Sustainability is the judicious use of thoughtfully selected resources to meet human needs while minimizing environmental impacts and waste. Designs for improving sustainability and IEQ both require purposeful control over how air, thermal energy (heat), and moisture enter, exit, and flow through the building.

Sustainable buildings feature air-tight envelopes, insulation, and glazing to control the movement of thermal energy. Fresh air enters the building through controlled ventilation instead of haphazard air filtration and leakage. These measures give sustainable buildings reduced heating and cooling loads compared to a similarly sized conventional building in the same region. Low sensible loads and energy-efficient mechanical equipment like Variable Refrigerant
Flow (VRF) zoning systems limit the building’s demand on the electric grid. Sustainable buildings also use all-electric mechanical systems and appliances where possible to limit or eliminate greenhouse gas (GHG) emissions from on-site fossil-fuel combustion. Superior control over how the building operates makes sustainability possible and creates opportunities to improve IEQ for occupants. For example, a VRF zoning system for smart heating and cooling keeps energy consumption to a minimum and uses the same level of precision to maintain occupant thermal comfort. Order and predictability enable developers, building owners, and project teams to truly design the indoor environment, rather than leaving it to chance.

Improving IEQ with VRF technology

VRF zoning systems deliver the precise amount of conditioning to each zone to satisfy heating and cooling loads while maximizing comfort. The systems are all-electric, require no fossil fuels, and include an outdoor unit and up to 50 indoor units connected by refrigerant lines.

VRF heat-recovery systems can provide simultaneous heating and cooling, making them suitable for multi-zone buildings with diverse thermal profiles such as dorms, multifamily applications, office buildings, hotels, and mixed-use facilities.

VRF controls help facility managers optimize heating and cooling with centralized equipment control and performance data. The insights, reports, and capabilities available through VRF controls support predictive maintenance and help coordinate complementary IEQ equipment for ventilation, filtration, and humidity control. VRF systems can also integrate with building automation systems (BAS) through standard communication protocols like BACnet.

IAQ Strategies and VRF Systems

To achieve high IAQ, contamination control strategies must mitigate contaminants like viruses, bacteria, allergens, dust, PM 2.5, and volatile organic compounds (VOCs). Strategies include source control, elimination, filtration, and dilution.

Source control means avoiding building materials and products likely to introduce contaminants (e.g., formaldehyde, other VOCs). In multifamily applications, this may include using all-electric appliances to reduce on-site combustion and indoor emissions.

Elimination can be accomplished with exhaust fans in areas like bathrooms or commercial kitchens.

Filtration removes airborne contaminants and particulates. The Minimum Efficiency Reporting Value (MERV) under ASHRAE 52.2 uses a scale of 1-20 to describe how effectively a filter can capture particles of a given size. For example, a filter with a rating between MERV 13 and 16 can capture particles larger than 0.3 microns. A High Efficiency Particulate Air Filter (HEPA) has capabilities in the range of MERV 17 to 20 and can be expected to remove 99.97% of airborne particles as small as 0.3 microns. As pleated filters increase in depth and efficacy, engineers must account for potential pressure drops and slower air movement. Every increase in efficacy comes with performance tradeoffs like a need for greater fan energy. Since April 2020, ASHRAE has recommended using MERV-13 filters or the highest level achievable for non-healthcare buildings.

Fresh outside air dilutes indoor contaminants including occupant CO2. In an airtight building designed to optimize IEQ, dilution is handled by the ventilation system. VRF systems are purpose-built for heating and cooling but can coordinate the operation of complementary ventilation equipment through controls. Depending on the region and application, the consulting engineer may specify an energy recovery ventilator (ERV), dedicated outdoor air system (DOAS), or outside air unit (OAU) to introduce and condition fresh, outdoor air. In addition to diluting contaminants, ventilation systems increase oxygen levels and can help control humidity. All three options are regulated by state and local codes developed from ASHRAE 62.1 and the International Mechanical Code.


IEQ and sustainability are complementary design objectives. Both are functions of enhanced control of building operation, and the methods for achieving one supports achieving the other. All-electric VRF systems can improve sustainability and IEQ by enhancing control of thermal comfort and energy use, coordinating IAQ equipment, and operating quietly. The public’s increased attention to how buildings operate and impact human beings may give healthy, sustainable commercial buildings a market advantage.

Joe Cefaly is Senior Manager of Applications at Mitsubishi Electric Trane HVAC US, where he provides engineering and applications support for both commercial and residential products. He’s worked at Mitsubishi Electric for 12 years, previously serving as a mechanical engineer in the Northeast. Joe is a LEED Accredited Professional and Certified Energy Manager. He earned a bachelor’s degree in physics from Union College and his MBA from Northeastern University.

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