Understanding WELL v2 certification

As WELL v2 certification becomes more prevalent, project managers, engineers and designers need to understand which preconditions and optimization features are impacted by the systems they design

By Richard Vedvik, PE, IMEG Corp., Rock Island, Illinois August 12, 2021


Learning Objectives

  • Understand the WELL v2 structure and certification.
  • Know the concept areas in WELL v2 that affect mechanical, electrical and plumbing system design.
  • Learn about the preconditions in WELL v2 that apply to MEP systems.

The International Well Building Institute WELL program considers occupant health concerns including both the perception of health as well as physical condition. This thought process follows the idea that the subjective attitude of building occupants can be correlated with the physical environment.

WELL v2 has 10 concept areas with 23 mandatory preconditions and an additional 97 possible optimizations. The 120 optimizations are labeled as “features” and are individually numbered by category. The 10 concepts are air, water, nourishment, light, movement, thermal comfort, sound, materials, mind and community. Certification requires either letters of assurance or performance verification in the form of testing on-site.

There are unique testing requirements for air quality, water quality, lighting, temperature and acoustics and the testing and sampling methods are defined in the WELL Performance Verification Guidebook. Verification may be a detailed performance test, a visual inspection or a spot check, as defined in the guidebook.

For some feature points, testing will be ongoing during occupancy through active monitoring and data logging. One of the aspects that sets WELL certification apart from other types of building design guidelines is the use of active monitoring and annual data submission.

How engineers can use WELL

As WELL certification becomes more prevalent, engineers should know how their systems are impacted. The International Well Building Institute was launched in 2014 with the first version of certification standards called WELL v1; the second version was issued in 2018 called WELL v2.

This article will focus on the impacts that each of the WELL v2 concept areas and associated features has on mechanical, electrical and plumbing systems in commercial (nonresidential) buildings. MEP engineers will have the greatest responsibilities in the concepts of air, water, light, thermal comfort and sound. It is important for MEP engineers and project managers to understand how the entire scorecard is structured; the goal of this article is to serve as a holistic primer for each concept.

The driving force behind the standard is promoting a healthy building environment that looks at the human experience with a holistic approach. The process has multiple steps and a substantial amount of documentation to help guide the design teams and develop the appropriate building scorecard. The scorecard can be thought of as a nutrition label for the building, providing a quick glance at how the building promotes health and wellness.

The scorecard results in certification at three levels: silver, gold and platinum. The design team will ensure all preconditions can be met within the project scope and budget, then choose optimizations based on the desired certification level with a secondary goal of providing a diverse scorecard.

There is an additional approach for shell and core buildings with multiple tenants. WELL core has four scorecard levels and is adapted to account for the spaces the building owner can and cannot control during design and construction.

Projects should know if they are going for WELL certification at the onset of the programming phase. Project registration is the first step in the process and basic building information is needed at this time. Additionally, the project will need to choose between WELL v1 and WELL v2 and the precertification process should identify the target compliance level.

Once registered, the project team will include certified professionals and a dedicated WELL reviewer, coaching support and a performance testing agent. WELL certification documentation is updated quarterly and designers should check regularly for updated information. For detailed information designers can reference “WELLographies,” which are white papers that are available on the IWBI website.


Improvements of air quality are believed to be linked to improved focus and alertness. Concerns of indoor air quality include adequate ventilation air (air that is from outside the building), interior contaminants, exterior contaminants, interior material off-gassing and microbial sources. There are four precondition categories. Feature A03, ventilation effectiveness, is the one that heating, ventilation and air conditioning engineers and designers will need to address.

The other preconditions are related to tobacco use on the property, the management of construction pollution and measurements of particulate matter organic gasses and inorganic gasses. Ventilation effectiveness compliance method depends on the system being either mechanically ventilated or naturally ventilated.

The mechanical ventilation system will be expected to meet one of four standards. Buildings pursuing natural ventilation methods have performative requirements based on the desired certification level. That is to say, a gold certification has more stringent requirements than a silver certification as it relates to parts-per-million.

In the United States, the applicable standard for either mechanical ventilation or natural ventilation is ASHRAE 62.1: Ventilation for Acceptable Indoor Air Quality for commercial buildings or ASHRAE 62.2: Ventilation and Acceptable Indoor Air Quality in Residential Buildings for occupancies classified as dwelling units. Within this standard, engineers will reference tables for minimum ventilation rates, minimum exhaust air rates, acceptable indoor air quality and requirements for various types of ventilation systems.

Feature A06, enhanced ventilation, can be pursued by providing enhancements to the ventilation requirements, which is to go above and beyond the minimum requirements in the precondition feature. Feature A07, operable windows, uses a design practice that the industry has moved away from. This feature includes points for managing the using of operable windows by using hourly monitoring of exterior air quality and temperature.

Active monitoring is a common theme throughout the air concept category and is focused upon in feature A08, air quality monitoring and awareness, which requires a system that logs data for reporting for annual submissions to maintain certification.

MEP engineers will also be engaged in the combustion management feature A10, combustion minimization, which either bans or limits the amount of emissions from combustion sources including water heaters and hot water boilers.

The requirements of particle filtration for ventilation systems are defined in feature A12, air filtration, which correlates outdoor air particulate thresholds with MERV ratings for filters and requires the pressure drop across the filter be monitored to alert staff when replacement is needed.

HVAC designers will be involved in feature A13, active volatile organic compound control, which can include activated carbon filtration to mitigate indoor levels of VOCs. Both A12 and A13 include ongoing reporting to ensure filter media are being maintained.

The last feature in the air concept category is microbe and mold control, for which ultraviolet emission can be used to control microbial growth on cooling coils in forced-air cooling systems. Additionally, interior humidity levels are managed to control interior condensation. Ongoing reporting is also required for this feature.


Drinking water quality is the primary focus of the water concept category. Plumbing system designers will need to coordinate with the local water utility for historical water quality at the site as well as design filtration systems to ensure drinking water properties are maintained. The need for adequate, daily water intake is well documented.

There are a variety of factors that affect the quality of drinking water and system designers will be faced with the challenge of quantifying water quality that enters the project site and then ensuring the water meets the prescribed standards.

Within this concept there are three precondition features and six optional features. Six of these features focus on controlling and mitigating harmful contaminants. Most of the aspects of these features require on-site testing as well as ongoing testing and reporting to ensure water quality thresholds are being maintained. All of the parts in feature W01, fundamental water quality; W02, water contaminants; W04, enhanced water quality; and W05, water quality consistency, require performance testing or ongoing data reporting.

Feature W08, hand-washing, affects the size of the sink and faucet selection to ensure the water column is of sufficient size and positioned to keep hands away from surfaces.


Historically, lighting was used for wayfinding and task illumination. Electric lighting or lighting-on-demand, has resulted in longer days and shorter evenings, which influences human health and stress. It has only been 100 years since half of the U.S. homes had electric light. Since the widespread adoption of electric lighting, our afternoons indoors do not have enough light and our evenings have too much light, compared to being outside.

It is difficult to ignore effects that artificial light has on the human body. We now know that the spectral density of lighting affects the circadian clock and its production of melatonin. Melatonin is made by our body but is naturally suppressed when our body interprets our surroundings as “daytime.”

The light concept has two preconditions features and six optimization features. Feature L01, light exposure and education, requires daylighting design meet a series of criteria that the lighting designer will need to coordinate with the architect. Two primary options are provided: either daylighting in common spaces only or daylighting in all spaces.

There are two main metrics used in this feature: spatial daylight autonomy and visible light transmittance. The spatial daylight autonomy metric is used to quantify the amount of daylighting that is present in a space relative to the total size of the space. It answers the question “Am I getting enough usable daylight in my space to promote well-being?”

Figure 3 provides output from a spatial daylight autonomy analysis. Visible light transmittance is a value that is associated with the optical property of exterior glazing and it indicates the amount of light that passes through the window. A higher value indicates an increased amount of light transmission. It is important to note that visible light transmittance is affected by the window frame. An enhancement to the precondition requirements is identified in feature L05, enhanced daylight access.

Feature L02, visual lighting design, is a precondition that relies on the Illuminating Engineering Society 10th Edition Handbook for indoor and outdoor lighting illuminance level recommendations. To verify compliance, the project verification includes annotated design documents and on-site performance testing. Lighting design used to be a process of calculating the foot-candles (or lux) at the task height and then choosing fixture locations that minimized shadows at the task location.

As color temperature options increased, designers started to consider how colors would be rendered. Color rendering may be architectural, based on surface finishes, or it could be for medical applications where the hue skin tone is important. More recently, the spectrum of color — not just the overall color temperature — is of interest.

One application of lighting color and spectrum is in feature L03, circadian lighting design. This feature requires that the lighting designer use the spectral data file for the lighting fixtures chosen to perform calculations at the vertical plane of the occupant’s eye location(s). Both melanoptic and photopic levels need to be quantified, as this feature sets a minimum equivalent melanoptic lux for regularly occupied spaces.

Another circadian metric is circadian stimulus, which looks at spectrum and also melatonin suppression levels. A CS of 0.7 means that 70% of melatonin is being suppressed (max measured). When CS is less than 0.1, amber lighting, there isn’t a measurable effect on melatonin suppression. With CS greater than 0.3, blue light, suppression is effective.

Feature L04 is glare control, which incorporates both interior and exterior lighting source glare control. The lighting designer and electrical designer will coordinate shade control that allows for either automatic control or occupant controls. There are additional requirements for manual controls to ensure daylighting is provided. Glare for interior luminaires requires luminance data and photometric information, and the designer needs to coordinate both the fixture selection, mounting height and the fixture orientation.

The concept of visual balance, identified in feature L06, visual balance, requires photometric study of uniformity between spaces and within the space. Glare from reflections is included in this feature, requiring surface finish coordination with the architectural design team.

Feature L07, electric light quality, continues the visual comfort approach of this concept. Luminaire selections will include specifications for color rending index or may comply with IES TM-30 fidelity, gamut and color rending index ranges listed in the feature.

Rounding out the light concept category is feature L08, occupant control of lighting environments, which defines requirements for lighting controls and relates to circadian tuning and occupant adjustment of lighting color in addition to levels.

Thermal comfort

The thermal comfort concept uses the same building systems (i.e., air handling units) as the air quality concepts, but uses a different series of metrics. Like the air concept, requirements are split between mechanically ventilated and naturally ventilated spaces. The mechanical system metric in prerequisite T01, thermal performance, and feature T02, enhanced thermal performance, are the predicted mean vote that uses heat balance concepts to describe thermal conditions and relate multiple comfort factors that an average person would agree with.

ASHRAE Standard 55: Thermal Environmental Conditions for Human Occupancy is a standard for thermal comfort that applies to projects in the United States. Features T03, thermal zoning, and T04, individual thermal control, relate to zoning and individual control, respectively. Building HVAC designs commonly combine multiple offices on a single zone to mitigate cost and feature T03 allows for multiple occupants.

While private offices are a fairly straightforward application of shared thermostats, an open office concept may be more complicated to implement. The heating systems in feature T05, radiant thermal comfort, are limited to hydronic or electric systems for at least 50% of the occupied areas. Radiant heating systems provide a substantial improvement to thermal comfort.

A computational fluid dynamics analysis was done for three different perimeter heating options along perimeter glass in a cold climate. Comfort is best achieved with consistent temperatures from head to ankles. This feature also includes a dedicated outdoor air system to achieve ventilation requirements. These systems offer energy savings by allowing for a variety of thermal control systems such as hydronic fan coil systems, chilled beams, variable refrigerant flow or even forced air systems that can be solely recirculation.

Feature T07, humidity control, is achieved by controlling relative humidity for at least 98% of operating hours during the year. The systems required to achieve this goal will vary based on physical location and will be affected by the arrangement of building entrances and locations used for taking humidity measurements. Control of humidity can be accomplished in a number of ways and will likely be accompanied by feature A14, microbe and mold control for ultraviolet treatment of cooling coils that will remove moisture from the air during the summer months.

There are two beta features within the concept that enhance the physical comfort of the site: T08, enhanced operable windows and T09, outdoor thermal comfort. Feature A07 is a precondition of feature T08 because both apply to operable windows. This enhanced point further refines operable window requirements and associates opening characteristics with seasonal temperatures. An interlock is required between window position and mechanical cooling operation, resulting in a likely need for sensors at each window to monitor the status. This enhancement feature further requires low openings during summer months and high openings during winter months, which needs to be coordinated with the architectural team for sensor positions and function.

Feature T09 rounds out this concept by awarding points for providing adequate shading by area or via temperature modeling of shading elements. This feature also requires a computational fluid dynamic study of wind speeds in areas designated as exterior seating to ensure wind speeds are not sustained at levels that would discourage use of exterior seating areas.


The aspects of a typical acoustical study will seem familiar to designers performing the calculations and preparing the necessary documents for the sound concept features. The only precondition is S01, sound mapping. Background noise level metrics can be either dBA (A-weighted overall sound pressure level) or noise criterion, known as NC. The acoustical designer will need to take all noise sources into consideration, both interior and exterior, to develop the necessary metrics.

Interior noise commonly includes HVAC systems, for which modeling is required. Exterior noise includes traffic, which can be modeled using software from the Federal Highway Administration. These calculations will provide overall dBA at the building façade, which the designer can use to correlate glazing transmission loss with interior noise contribution.

The second part of precondition S01 requires acoustical privacy be identified by listing the transmission loss metrics for demising walls and doors.

The third part of this feature includes identifying spaces as being either loud, quiet or mixed. This classification impacts decisions made to achieve optional features. The first optimization feature S02, maximum noise levels, identifies the maximum permissible noise levels for several pre-defined interior spaces. Higher points are available for quieter results during performance testing on-site. Feature S03, sound barriers, is related to S02 in that it quantifies transmission loss of demising partitions and doors, which contributes to a reduction in overall noise levels.

Feature S04, sound absorption, sets maximum permissible levels of reverberation time, labeled as RT60. This is the amount of time, in seconds, it takes a sound impulse to decay by 60 decibels. This metric is used to characterize a space as being “lively” or “dry,” and most occupants will relate “lively” to a room with noticeable echoes. To control reverberation time, sound absorption elements are typically added to the ceiling and walls and the second and third parts of this feature set quantities for surface treatments with a minimum noise reduction coefficient of 0.70.

The spaces identified as “quiet” in S01 are referenced in feature S05, sound masking, for scope of sound masking, with a maximum defined sound masking level. Other areas known for congregating — such as dining, corridors and open offices — have a higher sound masking level requirement. Impact insulation class is a measurement of noise transfer through floor-ceiling elements as a result of physical impact, i.e., footfall.

Feature S06, impact noise management, specifies minimum insulation ratings, all of which will require a resilient flooring solution to achieve.

Active speech amplification systems are identified in feature S07, enhanced audio devices, which focuses on speech intelligibility and accessibility though the use of audio equipment. Requirements are based on location and can be audio/video systems, public address systems or speech reinforcement systems, with separate requirements for each. The second aspect of this feature allows for individuals to have access to or away from the systems listed in this feature.

Hearing conservation is an important aspect for all employers and building owners to consider and feature S08, hearing health conservation, focuses on how noises can adversely affect occupants. Compliance with this feature requires access to hearing protection, compliance with applicable regulations and no-cost audiogram testing. This feature also requires the designation of a qualified supervisor that is responsible for the execution and maintenance of the conservation program.

This article focused on the concepts and associated features that heavily rely on MEP support, and designers can expect coordination with the entire design team as other features are pursued. Achieving compliance with nourishment, movement, materials, mind and community will require participation by all project designers.

Educational resources for building occupants occur in several concepts and features and MEP designers can assist the team for applicable information. Educational resources can include active monitoring results for air quality using the building automation system or information on healthy options for water, nourishment, light and movement.

There are additional points available for innovation aspects that provide designers with additional freedoms to exceed requirements with a focus on the goals and mission of WELL. As designers become more familiar with the concepts and features within the WELL certification system, a similar holistic approach to building design is likely to become prevalent in noncertified building designs.

Author Bio: Richard Vedvik is a senior electrical engineer and acoustics engineer at IMEG Corp. Vedvik has experience in the health care, education, commercial and government sectors. He is a member of the Consulting-Specifying Engineer editorial advisory board.