This credit presents teams with a broad array of different strategies for maintaining healthy indoor air quality. Teams can pursue three strategies for one point or six strategies for two points.
The IAQ strategies outlined under LEED v4.1 can be achieved with varying degrees of difficulty (and cost), depending on your project design and other sustainability and performance goals. Be sure to review and understand the requirements of each strategy within the context of your building before committing.
Strategy 1. Entryway Systems
Entryway systems are a simple and effective way to prevent occupants bringing dirt and particulates into the building. These may include built-in products like grates, grilles, and slotted flooring systems, or temporary products like rollout mats.
As well as meeting the dimensional requirements (note: the 10-foot length must be in the primary direction of travel), all regularly used entryway systems must be permanent—meaning any rollout mats must be there all year round and not just brought out during wet or icy weather. Building O+M plans should also include weekly cleaning of entryway systems to ensure they continue to work effectively.
Strategy 2. Interior Cross-Contamination Prevention
Some necessary functional spaces within buildings, such as garages, janitors’ closets, and print/copy rooms, generate air pollutants as part of their normal function. Similar to previous iterations of this strategy, LEED v4.1 awards projects which effectively isolate and remove such pollutants before they have a chance to enter other areas of the building.
Isolating means pollutant producing spaces are fully enclosed with deck-to-deck (floor-to-ceiling) partitions and include self-closing doors. To meet exhaust requirements, each pollutant producing space must be negatively pressurized with respect to adjacent spaces in accordance with IEQp1 or a minimum exhaust of 0.5 cfm/sf.
Projects may benefit from locating pollutant-producing spaces towards the core of the building, which can limit duct runs and simplify the exhaust system.
Strategies 3 & 4. Filtration Systems
Minimum Efficiency Reporting Value (MERV) rating, designed by ASHRAE, is used to identify the effectiveness of filters to capture particulate matter. Scores range between 1 and 16. MERV 16 filters are identified as high-efficiency particle filters that are often used in healthcare facilities and labs but have, in some cases, been adopted in commercial and residential buildings during the COVID-19 pandemic. The design team needs to choose a minimum of MERV 13 to meet the credit requirement. However, in locations with high outdoor PM2.5 and PM 10, it is highly recommended to implement a higher MERV filter and change filters more frequently.
The MERV requirement applies to both fresh air filtration and recirculated filters. Please note that often ventilation systems have a set of prefilters with a lower MERV, and the requirement only applies to the main filters.
Strategies 5 & 6. Increased Ventilation
Increased ventilation significantly improves indoor air quality and has been a major strategy implemented during the COVID-19 pandemic to prevent the spread of disease. Increasing ventilation can also potentially result in a larger ventilation system with higher capacity but cannot be implemented on a system designed to provide minimum fresh air. The other consideration before pursuing these strategies is to ensure that you are aware of the energy penalty due to increased ventilation. Per the Energy Performance Requirement, the baseline energy model should still consider minimum required fresh air versus the proposed case’s fresh air flow.
If the project is under a more stringent ventilation code, like the Chicago Ventilation code, you might be able to automatically achieve this strategy. Additionally, since it would be a code requirement, you can avoid the energy penalty too.
Strategy 7. Operable Windows
Providing access to operable windows to 75% of occupants depends on the building type and function, but for most residential buildings it will not be a barrier. For other building types, providing operable windows requires early coordination and analysis to incorporate them into the design.
Strategy 8. Engineered Natural Ventilation
Engineered natural ventilation is consistent with the natural ventilation compliance path under the Minimum Indoor Air Quality Performance prerequisite.
Strategy 9. Carbon Dioxide Monitoring
This strategy only requires monitoring, which is required as a part of demand-controlled ventilation in the International Energy Conservation Code (IECC) and ASHRAE 90.1, so in many locations, this strategy should be automatically achieved since many energy codes across the U.S. are more stringent than the credit. Please note that LEED identifies densely occupied spaces as spaces with more than 25 people per 1,000 square feet, which may not be aligned with energy codes.
Strategy 10. Additional Source Control and Monitoring
This strategy is new strategy and is highly recommended. The strategy is advocating for a more sophisticated air quality monitoring system that covers more pollutants than CO2, including, but not limited to, PM2.5 and 10, total VOCs, ozone, and others. Having a multi-contaminant monitor is going to help the project to identify different sources of pollution and take action to minimize them. Compared to a simplified, CO2-driven ventilation strategy, which is only accounting for occupancy, this path could result in much better air quality in the space.
What’s New in LEED v4.1
- The point structure has changed, with three strategies for one point or six strategies for two points.
- New strategies have been added.
- For filtration, the credit now references ASHRAE 52.2–2017 (instead of 2010) and ISO 16890-2016 (instead of CEN Standard EN 779–2002).
- For CO2 monitoring, the referenced standard has been updated to ASHRAE 62.1–2016 (formerly 2010).
Should I upgrade?
The updates here are fairly minor, so pursuing a substitution is probably unnecessary; however, some new strategies would be beneficial, if possible, like strategy 10.