EPA Indoor airPLUS and Radon Resistant Construction

One of the prerequisite programs required for PHIUS+ Certification is the EPA’s Indoor airPLUS Program.  Born out of a need to minimize indoor air pollutants, the EPA dove-tailed this program with the ENERGY STAR Labeled Homes Program, which is also a prerequisite for the home or dwelling unit to earn both Indoor airPLUS and PHIUS+.  This serves to ensure that the dwelling unit is relatively tight, insulation is properly installed, the HVAC systems are properly sized, and bulk moisture throughout the building assembly is properly controlled.

Read the full technical bulletin here.

Indoor airPLUS then takes indoor air quality to the next level. Integrating the Construction Specifications and Checklist requirements into the design, homes/dwelling units can then be verified to ensure greater precautions are taken for moisture control and dehumidification, air intakes are protected from birds and rodents, HVAC systems are kept clean, better filter media is used, and potential sources of moisture and contaminants are vented to the outdoors. Additionally, HVAC systems and ducts are prohibited in garages, pollutants from combustion equipment are minimized, and low VOC products are used.

One of the unique and important aspects of Indoor airPLUS is the requirement for radon-resistant construction measures in EPA Radon Zone 1. If you are not familiar with the Radon Zone map, it can be found here:  https://www.epa.gov/radon/epa-map-radon-zones.

Radon is a naturally occurring radioactive gas that can cause lung cancer. In fact, the EPA estimates that 21,000 deaths each year in the U.S. are attributable to radon exposure. The EPA has very good resources to read up on the health risks of radon. Their site can be found here: https://www.epa.gov/radon/health-risk-radon#head.

So why should PHIUS stakeholders be concerned with this? As mentioned above, PHIUS relies heavily on prerequisite programs such as ENERGY STAR and Indoor airPLUS. Since the airtightness standards for PHIUS Certified projects are up to 10 times more stringent than a typical code-built home, dilution of the indoor air cannot occur as readily. PHIUS ventilation requirements go well beyond those of systems found in typical Code built or even Energy Star Labeled homes. Good ventilation design, whether for code or for PHIUS starts with source control, i.e. minimizing the source of contaminants along with proper ventilation.

An example of a passive radon system.

In high risk areas such as Radon Zone 1, EPA Indoor airPLUS requires installation of a passive radon system, at minimum. EPA also recommends utilizing active radon systems to further reduce radon concentrations in the home, although this is not yet an Indoor airPLUS requirement. The most modern radon standards are developed through an ANSI-accredited consensus process by the AARST Consortium (American Association of Radon Scientists and Technologists). EPA recommends following the ANSI/AARST CCAH Standard for 1-2 family dwellings and townhouses (max. total foundation area of 2500 sq. ft.) or the ANSI/AARST CC-1000 Standard for larger foundations, which often apply in multifamily buildings. However, the key components of a passive radon system for the purposes of Indoor airPLUS verification are succinctly outlined in Item 2.1 of their Construction Specifications.

ANSI/AARST will soon publish updated standards to provide guidance for the design and installation of two radon system options in new low-rise residential buildings. These systems, passive and powered, are designed to reduce elevated indoor radon levels by inducing a negative pressure in the soil below the building. The practice provides design and installation methods through soil depressurization systems that can be installed in in any geographic area.

Each of the two options consists of soil gas collection and a pipe distribution system to exhaust these gases. The first standard is for the design of passive radon reduction systems, sometimes referred to as a “radon rough-in” (ANSI/AARST RRNC). The second newly updated standard (anticipated in early 2020) includes details for a fan-powered radon reduction system, as well as radon testing (ANSI/AARST CCAH). Passive systems can result in reduced radon levels of up to 50%. These standards suggest that when radon test results for a building with a passive system are not acceptable, the system be converted to fan-powered operation. Typically, the action level is 4 pCi/L (Picocuries per liter). If the tested radon level exceeds 4pCI/L, then a fan is added to further depressurize the soil and positively vent the gas to the outside.

Recently, the EPA Indoor airPLUS team sent out this Technical Bulletin. The Technical Bulletin provides simple guidance on the installation of passive and active radon systems. Please pay particular attention to the drawings in the Bulletin, and note that the active system depicted has the fan located in a vented attic. This is outside the pressure/thermal boundary of the home. This has special significance with homes/buildings constructed to PHIUS Standards, because often, the attic space is WITHIN the pressure/thermal boundary of the home. Therefore, the fan cannot be located in the attic and must be outside the pressure/thermal boundary. The reason for this is, should there be a failure on the discharge or pressurized side of the fan, the building can actually be filled with radon gas.

Some other precautions that include a tight seal at the slab and vapor barrier to the vertical riser. Additionally, ensuring the riser is clearly labeled as “RADON” to minimize the chance that a plumbing waste line will be accidentally connected to it in the future is also important.

Tony Lisanti CEM, CPHC
PHIUS+ QA/QC Manager

With thanks to Nicholas Hurst from the EPA Indoor airPLUS Team