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Indoor airPLUS Version 2: What Changes Are Coming?

The US Environmental Protection Agency (EPA) is adding a second level to its Indoor airPLUS specification for homes and residential buildings. What does this mean for building designers, developers, owners, and property managers that earn the Indoor airPLUS label for their buildings? Below, we have an overview of the changes to expect when Indoor airPLUS version 2 is launched.

If you’re new to Indoor airPLUS and are here looking for ways to improve indoor air quality (IAQ) and occupant health as part of your projects, you’re in the right place. We’re starting with an overview of the Indoor airPLUS specification:

Quick Refresher: What is Indoor airPLUS?

Americans spend up to 90% of their time indoors, where, according to the EPA, they can be exposed to indoor air pollutants associated with irritation of the eyes, nose, and throat; headaches, dizziness, and fatigue; and respiratory diseases, heart disease, and cancer.

Asthma, the most common chronic disease among children according to the World Health Organization, can be triggered by indoor air pollutants. The National Institute of Health says that living in substandard housing often leads to exposure to triggers and higher rates of allergen sensitization. EPA identifies those triggers as:

  • Secondhand smoke
  • Dust mites
  • Molds
  • Cockroaches and pests
  • Pets
  • Nitrogen dioxide
  • Outdoor air pollution
  • Chemical irritants
  • Wood smoke

Building designers, developers, owners, and property management companies have direct control over nearly all these triggers.

At SWA, we work with these entities to make buildings perform better. While the goal is often to reduce energy usage, water usage, material consumption, and carbon emissions, these efforts are futile if building occupants don’t feel safe, healthy, and well.

Indoor airPLUS is one pathway to deliver healthier buildings. The specification was developed in 2008 to build upon the energy efficiency and durability measures in the ENERGY STAR® program.

Whereas ENERGY STAR is the next step to performing better than code, Indoor airPLUS (which requires ENERGY STAR as a base program) builds upon the indoor air quality, water management, and durability measures of ENERGY STAR. The next level evolved to DOE Zero Energy Ready Homes (ZERH) in 2013. Passive House Institute US (PHIUS) formed in 2007 and began requiring ZERH in March of 2015.

Tiers above energy code and ENERGY STAR program: Indoor airPLUS, Zero Energy Ready Homes, and Passive House Institute US.

Image source: EPA

Indoor airPLUS Version 2: What to Expect

EPA drafted Indoor airPLUS version 2 to push the market forward while being mindful of added costs. This second level improves IAQ across the spectrum of new and existing housing stock while addressing affordability and creating opportunities for disadvantaged communities and populations to get access to safe, healthy housing.

The second public comment period for Indoor airPLUS version 2 just closed. EPA’s technical advisory team is replying to each and every comment with the intention of having the specification ready for use in early 2024.

Significant Changes

Here are a few of the most significant proposed changes for version 2:

Two levels: There will be two levels of certification. The base specification will not require ENERGY STAR certification and will have a lot of requirements accommodating existing homes and multifamily buildings.

Performance based: The more rigorous level, Gold, will require ENERGY STAR certification and incorporate additional performance-based metrics.

Required radon testing: Radon testing will be required, regardless of the radon zone in which the project is located. Radon is the number one cause of lung cancer among non-smokers and causes more than 20,000 deaths per year—which is why testing will be required for all Indoor airPLUS v2 labeled projects.

IAQ monitoring: There is proposed air quality monitoring in rooms that contain solid fuel burning appliances, like wood fireplaces.

Water detection: Water leak detection will be required for below-grade spaces, like basements.

Other Enhancements

The following enhancements coming in version 2 will help achieve optimal indoor air quality:

Filters: Filters must be MERV 11 (certified) or MERV 13 (Gold).

Portable air cleaners: Non-ducted (i.e., mini-split, hydronic, etc.) heating and cooling systems must also have stand-alone portable air cleaners for each of the two largest living spaces.

Combustion pollutant control: Ventilation must be balanced and feature outdoor air-measured (Gold) combustion pollutant control; no combustion equipment can be used within the home’s pressure boundary unless mechanically drafted or direct-vented.

Emissions standards: Material emissions must meet rigorous California Department of Public Health (CDPH) testing standards.

EPA Indoor airPLUS: Materials, Radon, Moisture Control, Combustion Pollutants, Pest Barriers, and Ventilation and Filtration.

Image source: EPA

The Bigger Picture

Currently, Indoor airPLUS version 1 is available for any residential project, regardless of size or height, that is receiving ENERGY STAR certification. For single-family homes and duplexes, that means the ENERGY STAR Homes program. For all other residential buildings, that means the ENERGY STAR Multifamily New Construction (ESMFNC).

Most raters are transitioning from ESMFNC v1.1 to v1.2 since the 45L incentive, updated in the recent Inflation Reduction Act, will require ESMFNC v1.2.

Also under revision, the ZERH v2 program drives all-electric buildings and recently closed its first public comment. The 2024 IECC draft is moving in a similar direction with electric vehicle-ready charging, tighter air-leakage testing thresholds, and more efficient equipment requirements.

The ENERGY STAR program’s commitment to no-less-than 10% better than code means that each next-step program—Indoor airPLUS, ZERH, and PHIUS—will continue to build rigor and results into their programs.

EPA’s technical advisory team is doing this with the Indoor airPLUS version 2 specification by weighing valuable stakeholder feedback and recognizing the challenge of improving IAQ while increasing program participation.

SWA & Indoor airPLUS

SWA is proud to play a role in the development of Indoor airPLUS version 2. SWA became an Indoor airPLUS partner in 2011 and has received the Indoor airPLUS Leader Award for 11 consecutive years.

Gayathri Vijayakumar‘s experience providing technical support to ENERGY STAR and as a member of the 2024 IECC development committee has been invaluable during the four revisions of Indoor airPLUS v1. And our involvement has increased through the development of Indoor airPLUS version 2. SWA’s Director of Building Enclosure Services, Bill Zoeller, has given critical feedback about moisture management and durability items. Scott Pusey has weighed in on ventilation and testing procedure issues. He, along with Steve Klocke and several SWA raters, gave feedback from a field person’s perspective. That pragmatic approach is critical to the development of standards and specifications where strategies are practical and implementable in the field.

Have questions about Indoor airPLUS, IAQ, or occupant health? Fill out our contact form to speak to one of our IAQ experts.

Karla Butterfield of Steven Winter Associates.


Written by Karla Butterfield, Sustainability Director on SWA’s Residential Building Services Team



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