Indoor Air Quality Score Calculator

CO2 Level (ppm) affects two of the six sub-scores at once: it sets the CO2 sub-score directly (max 20 points), and it also feeds the source-control sub-score (max 10 points), which is derived partly from CO2 and partly from VOC readings. Filter MERV Rating only affects the filtration sub-score (max 20 points) and nothing else, so the same percentage change in CO2 Level moves IAQ Score by more.

The ventilation sub-score (worth up to 25 of the 100 IAQ Score points) caps out once Outdoor Air Supply reaches 1.5 times the ASHRAE 62.1 Required CFM for your Floor Area and Number of Occupants. Once you are already supplying that much outdoor air, more CFM keeps raising the displayed Ventilation Adequacy (%) percentage (which has no cap) but stops adding further points to IAQ Score, since the ventilation sub-score has already reached its own maximum.

The humidity sub-score (10 of the 100 IAQ Score points) is flat at its maximum anywhere inside the ASHRAE-recommended 40-60% relative humidity band -- there is no bonus for landing closer to the middle of that range. IAQ Score only starts losing humidity points once Relative Humidity (%) drifts outside 40-60%, where the sub-score declines toward zero as it approaches the extremes below 20% or above 80%.

Yes -- Total VOCs (µg/m³) sets the VOC sub-score (max 15 points) directly, and it also contributes to the source-control sub-score (max 10 points) alongside the CO2 reading, since low VOC and CO2 levels together are read as a proxy for good pollutant source control. So a change in Total VOCs moves IAQ Score through two sub-scores at once, even though only one output, VOC Score (of 15), reports the direct component.