What Is the WELL Building Standard?

The WELL Building Standard is a performance-based certification system for buildings and organizations that focuses on human health and wellbeing. Developed by the International WELL Building Institute (IWBI) and launched in 2014, WELL evaluates how the built environment impacts the health, comfort, and productivity of the people who occupy it.

Where LEED focuses primarily on the environmental impact of buildings (energy use, water consumption, materials, site), WELL focuses on occupant impact. WELL and LEED are complementary — many projects pursue both certifications simultaneously — but they address different outcomes. A building can be LEED Platinum and have poor indoor air quality, inadequate lighting quality, or thermal discomfort. WELL addresses those gaps.

WELL v2, released in 2018 and the current active version, organizes requirements across 10 concepts, each containing precondition features (required for certification) and optimization features (points-based, for higher certification levels). WELL certification is achieved at Bronze, Silver, Gold, or Platinum levels based on the number of optimization points earned.

The 10 WELL Concepts

Air: Targets indoor air quality through ventilation rates, filtration, pollutant limits, source control, and monitoring. Requirements go beyond ASHRAE 62.1 minimums — WELL Air specifies particulate matter (PM2.5, PM10) concentration limits, VOC limits, CO₂ limits (typically 1,100 ppm above outdoor air), and formaldehyde limits. Continuous IAQ monitoring with visible displays is a common optimization feature.

Water: Addresses drinking water quality at the point of use — not just at the building entry point. WELL Water requires testing for microbiological contaminants, heavy metals, and disinfection byproducts. It also requires filtered water access at regular intervals throughout the building and specifies plumbing materials that minimize leaching.

Nourishment: Addresses food options available in the building — fresh produce availability, nutrition labeling, portion sizing. Primarily relevant to large employers with cafeterias; limited MEP design impact.

Light: One of the most impactful WELL concepts for electrical engineers and lighting designers. WELL Light targets both visual acuity (adequate illumination levels) and circadian health (appropriate light spectrum and intensity at different times of day). Key features include minimum illuminance on work surfaces (500 lux), limits on glare (UGR ≤ 19), and circadian lighting requirements — providing high color-rendering, blue-enriched light during daytime and reducing blue-wavelength light in the evening in spaces used in the evening. Tunable white LED systems that shift color temperature throughout the day are a common WELL Light compliance strategy.

Movement: Encourages physical activity through building design — accessible stairways, sit-stand workstations, active furnishing, exercise facilities. Primarily an architectural feature but affects MEP in terms of gym and stairwell HVAC and lighting design.

Thermal Comfort: Directly relevant to HVAC engineers. WELL Thermal Comfort requires individual thermal control or demonstrates compliance with ASHRAE 55 thermal comfort standards across all occupied zones. Personal environmental control systems (PEC) — individual occupant control of temperature, airflow, and radiant temperature — are a key optimization feature. Underfloor air distribution (UFAD) and active chilled beams are frequently used to provide the zone-by-zone control WELL Thermal Comfort rewards.

Sound: Addresses acoustic performance — background noise levels (HVAC noise criteria NC 35–40 for offices), speech privacy (sound transmission class ratings between spaces), and reverberation time in open plan areas. HVAC equipment selection, duct design, and vibration isolation have direct implications for WELL Sound compliance.

Materials: Targets hazardous material reduction — VOC limits for paints, adhesives, and finishes; restrictions on certain flame retardants and plasticizers in furniture; HVAC duct liner VOC emission limits. Relevant to MEP in terms of specifying low-emission ductwork, pipe insulation, and equipment finishes.

Mind: Addresses mental health and cognitive performance — biophilic design elements, spaces for rest and restoration, access to nature and views. Limited direct MEP impact but affects daylighting design and specification of circadian lighting.

Community: Addresses equity, inclusivity, and access — ADA compliance, lactation rooms, emergency preparedness plans. Some MEP touchpoints related to accessible restrooms and emergency systems.

Key MEP Design Implications

Ventilation: WELL Air typically requires outdoor air rates 30–50% above ASHRAE 62.1 minimums. Combined with WELL's filtration requirements (MERV 13 minimum for air handlers serving occupied spaces), this increases AHU sizing, filter housings, and fan energy. Energy recovery ventilation becomes more important at higher outdoor air rates to offset the energy penalty.

Filtration: MERV 13 filtration (minimum) is required by most WELL Air preconditions. Many MERV 13 filters have significantly higher pressure drop than the MERV 8 filters many systems are designed for — AHU fan sizing and static pressure calculations must account for this. Filter housings must be accessible for replacement, and replacement schedules must be established in the building operating plan.

IAQ monitoring: WELL Air optimization features typically require continuous monitoring of CO₂, PM2.5, VOCs, and temperature/humidity. This requires a network of sensors throughout the building, a monitoring platform to collect and display data, and an alert system that notifies building operations when concentrations exceed limits. Integration with the BAS is common.

Lighting controls: WELL Light circadian requirements drive specification of tunable white LED systems with time-based control schedules. Controls must be programmable to adjust color temperature (CCT) throughout the day — higher CCT (5000–6500K, blue-enriched) in the morning and afternoon, lower CCT (2700–3000K) in the evening for spaces occupied at night. Standard on/off and dimming controls are insufficient for WELL Light optimization features.

WELL vs. LEED: How They Complement Each Other

WELL and LEED can be pursued simultaneously with significant synergy. Both require energy modeling (LEED EA, WELL Energy concept), both reward IAQ monitoring and commissioning, and both credit high-performance HVAC design. Many WELL preconditions align with LEED EQ credits.

The primary tension between WELL and LEED is in ventilation energy: WELL requires more outdoor air, which increases HVAC energy and makes LEED energy performance harder to achieve. Energy recovery ventilation is the standard solution to resolve this tension — recover energy from exhaust air to condition the additional WELL-required outdoor air with minimal energy penalty.