Adequate air quality is an integral part of healthy indoor environments. To comply with green building standards, project teams need to conduct air quality assessments before and during occupancy. In this blog post, we will explore how air quality is evaluated according to LEED Building standards.

Photo by Esaias Tan on Unsplash

What is the LEED standard?

The LEED (Leadership in Energy and Environmental Design®) certification is a globally recognized building rating system developed by the US Green Building Council in 1998. The standard applies to various types of buildings – from homes to commercial buildings – and different types of construction phases – from the design stage to existing buildings.

Buildings receive points according to nine categories and depending on their overall score, different certification levels are awarded: Silver, Gold, and Platinum.

Air quality in the LEED standard

Green building evaluation systems include different categories, but they all measure how good the air is inside. According to researchers, the average contribution of indoor air quality to green building schemes worldwide is 7.5%.

Depending on whether the facility is new/just renovated or already existing, the council sets different requirements for air quality monitoring. So, here we will divide buildings into two groups:

  • First group: newly built or renovated;
  • Second group: already occupied for more than a year.

First group: Air Quality Monitoring for BD+C and ID+C

Monitoring air quality can earn two points for both new buildings that just have been built or renovated (Building Design and Construction, or BD+C) or commercial interiors such as office spaces or hotels that are a complete interior fill-out (Interior Design and Construction, or ID+C).

Indoor Air Quality Assessment scores 2 points both for BD+C and ID+C.

The Indoor Environmental Quality category in LEED v4 for BD+C: New Construction and Major Renovation. Source: Scribd

Indoor Air Quality Assessment: Flush-Out VS Air Testing

Project teams can opt either for flush-out before and during occupancy (one point earned) or air testing before occupancy (two points earned).

Flush-Out is the process of forcing a specific amount of outdoor air through the building which requires several weeks to complete and a lot of resources. The idea behind this process is to remove pollutants that off-gas from new paint, finishes, and materials.

Air testing is conducted after setting up all interior finishes, but prior to occupancy. This method has its own advantages. First, the building owner can earn two points by sampling the air for all required air pollutants. Second, it isn’t as time-consuming as Flush-Out. Finally and most importantly, air testing adds more value in the long-term as the actual air sampling provides more tangible results compared to flushing the building as chemicals will only be flushed out for a period of time.

Air Testing for BD+C and ID+C

The project team needs to test the air before occupancy, but during normal ventilation operations.

To earn 1 point, the building owner should conduct tests for:

  • Particulate matter PM2.5;
  • Particulate matter PM10;
  • Carbon monoxide (CO);
  • Ozone (O3).
Source: USGBC

For an additional point, VOC testing is possible.

Source: USGBC

LEED Pilot Credits for BD+C: Performance-based indoor air quality design and assessment

Besides regular assessment procedures, the US Green Building Council introduces Pilot Credits on a regular basis, new credit requirements proposed by USGBC members for testing. These credits are temporary and will likely be applied for using the “Innovation in Design” form when submitting documents. This way USGBC seeks new innovative methods to assess indoor environments. If the pilot credits receive positive feedback from members, they may be included in future LEED versions.

For example, recently a new pilot credit “Safety First: Managing Indoor Air Quality during COVID-19” was introduced to the LEED O+M rating system. It focuses mostly on improving ventilation and air filtration without considering the level of air pollutants inside the building. However, a high level of particles in the air is associated with a greater chance of transmitting viruses which we investigated through research in this blog post.

Other pilot credits that actually incorporate measuring air pollutants in new buildings refer to LEED BD+C: Performance-based indoor air quality design and assessment (max 7 points).

Here are the main takeaways from these requirements:

Tier 1. Contaminant-based IAQ Design (1 point)

  • Design and perform engineering analysis to make sure indoor contaminants don’t exceed maximum concentrations. The list of target contaminants is provided further below.
  • Air cleaning devices should be tested for not producing harmful byproducts such as ozone, formaldehyde, etc.
  • Air monitoring devices should be installed at all times.

Our little comment: If you are wondering how it’s possible that electronic air devices produce harmful pollutants, think of air scrubbers – some models generate ozone.

Tier 2. Baseline IAQ evaluation (1-3 points)

The building owners should test indoor and outdoor air quality and conduct an occupant satisfaction evaluation. Tests and surveys should be conducted 30 to 60 days after the issuance of a certificate of occupancy.

  1. LEED-specific contaminant list (2 points, the table is below)
  2. And project-specific contaminant list (1 point). Meanwhile, a minimum four air pollutants must be measured: formaldehyde, TVOC, CO2, and PM2.5.

Tier 3. Demonstrate IAQ performance (3 points)

In the end, the project team should demonstrate IAQ evaluation, where the concentration of air pollutants shall stay at or below the concentration limits and occupant acceptability is at or above 80%.

Mandatory indoor VOC contaminant testing
Mandatory inorganic contaminant testing

This is the alternative method of getting air-quality related credits from the Indoor Environment Quality category.

Points allocation

Regular air quality monitoring is a good option for building owners as it guarantees constant monitoring of occupants’ wellbeing and the opportunity to take immediate actions on improving air quality if the monitoring system is integrated with HVAC.

Atmocube, an air quality monitoring system for commercial buildings, tracks major air pollutants and may be customized for specific project needs, i.e. adding new sensors or new module design.

Atmocube

Second group: Air Quality Monitoring for Existing Buildings

Fully operational buildings or those occupied for more than a year are evaluated according to the LEED Operations and Maintenance rating system (O+M).

The category responsible for monitoring air pollutants is called Indoor Environmental Quality Performance. Check pages 40-43 in the guide for detailed score calculations.

The building owners should conduct a yearly occupant satisfaction review and air quality evaluation. Based on these rates, the human experience score is calculated and adds up to a maximum of 20 points:

  • Occupant satisfaction score (50%);
  • CO2 score (25%);
  • TVOC score (25%).