Indoor air quality (IAQ) is of great value to homeowners, builders, energy auditors, and codes-and-standard bodies. Lawrence Berkeley Laboratory (LBL) is developing new IAQ metrics that will provide an easy-to-understand IAQ score.

Audiences for IAQ Metrics

IAQ metrics are for building-industry professionals, including energy auditors, energy raters, and home inspectors.  However, the index or score must be easy to understand for the general public. A single numerical score would be preferable. Discussions with builders indicate that they like the idea of a numerical score or rating. The IAQ score allows users to compare different homes in marketing strategies, get credit for a home with better IAQ, and to evaluate how best to invest in home upgrades. The IAQ score is analogous to the $/point exercise energy raters currently use for home energy ratings.

What new IAQ metrics will include

Among the most important goals of scoring is to build upon IAQ characteristics that are easy to observe and report. Researchers are working on methods of valuing IAQ such as these.

  • One important IAQ-related characteristic is the asset rating, like the asset ratings of a home appraisal. Asset ratings include paint condition, number of bathrooms, and number of bedrooms. The asset rating doesn’t consider the behavior of the current occupants but only the characteristics of the home itself.
  • Another important IAQ -related characteristic is outdoor air quality. If the outdoor air is polluted, the home may need filtration and air-tightening to prevent outdoor air from polluting indoor air.
  • A new IAQ score or index may need to consider that the indoor air quality within a home varies from one room to another. Therefore, the mitigation strategies for solving IAQ problems may need to vary room-to-room accordingly.

Scientists are working toward a method for scoring indoor air quality (IAQ). This score would be similar to energy scores like the HERS Index (HERS = Home Energy Rating Systems). The HERS Index rates homes from 150 down to zero — zero being the best rating and denoting that the home is a net zero energy home. Homes with higher IAQ scores would have more indoor air pollutants than homes with lower scores. With the IAQ index, 150 would represent a home with very poor indoor air quality and a zero would represent exemplary IAQ.

IAQ Index – Determining Points

The number of points are based on the following three factors.

  1. The hazard type and level
  2. How much that an observable feature mitigates the hazard
  3. The usability, effectiveness, durability, and limitations of the mitigation strategy

Then you combine three separate sub scores as described above, those being health, odor, and moisture. The IAQ index with base health score on disability-adjusted life years (DALYS). Scores for odor and moisture would be less precise and more subjective.


  • Use DALYs based on contaminants of concern and their likely concentrations
  • Based on existing literature, plus current and soon to be started field studies


  • Various indexes: mean RH, hours above RH limit, number of times above RH limit for more than 24 hours… etc.
  • Adapt ASHRAE 160 Mold Index (currently LBNL using this in Attic study for CEC)


  • Most sources are from occupants
  • Could use CO2 or RH as a surrogate for bioeffluents?

More information from Saturn books and courses

ASHRAE 62.2 Ventilation Standard Mini Course (2.5 CEUs)

Whole-Building Ventilation Short Course (8.0 CEU)

Indoor Air Pollutants Mini Course (1.5 CEUs)

Also see this LBL website