Ventilation Controls: Meeting Code and Managing IAQ – GreenBuildingAdvisor

By Jon Harrod | December 11, 2025

Getting the right amount of ventilation air is important. We need enough to dilute pollutants, but too much can drive up heating and cooling costs. Excess ventilation can also make homes dry and drafty in winter and harder to dehumidify in other seasons.

How much ventilation is enough? Beginning in 2012, the International Residential Code (IRC) set whole-house airflow requirements based on square footage and number of bedrooms. These prescriptive targets are a good starting point, but they don’t account for differences in occupancy or behavior.

Imagine a family of five living in a 2000-sq.-ft., three-bedroom house. They have a gas cooktop and use conventional cleaners and air fresheners. Now imagine an identical house with two occupants, an induction cooktop, and nontoxic household products. The two homes might have very different levels of CO2, volatile organic compounds (VOCs), and fine particulate matter (PM2.5). But under the IRC, their ventilation targets are the same.

Pollutant loads also change over time. VOCs may off-gas from building products over months or years. CO2 levels are low when a house is empty, rise when occupied, and reach peak levels during large gatherings. Cooking can drive short-lived spikes in PM2.5, even when kitchen exhaust fans are turned on.

Moisture and pollutant concentrations in the outdoor air are also variable. That’s why ventilation in winter—when outdoor moisture levels are low—helps keep a house dry, while ventilating with humid summer air can make moisture problems worse. Bringing in polluted air—for example, during smog or wildfire events—can also hurt indoor air quality.

Ventilation controls allow us to adjust the rate of air exchange. In this article, I’ll walk through the steps to select and configure a basic set of controls. These controls will deliver a baseline airflow rate that matches code requirements.…