HVAC efficiency and indoor air quality in airtight homes

Modern home construction and energy-efficiency upgrades, such as spray foam insulation and high-efficiency windows, are creating increasingly airtight building envelopes. While this reduces drafts and energy bills, excessive airtightness can lead to poor indoor air quality, excess humidity, and pressure imbalances. The U.S. Environmental Protection Agency notes that indoor air can be two to five times more polluted than outdoor air, often due to insufficient fresh air exchange.

In coastal or subtropical regions, humidity significantly impacts perceived temperature and HVAC performance. High relative humidity slows sweat evaporation, making rooms feel warmer than the thermostat indicates. Effective cooling in these environments requires systems that prioritize moisture control alongside temperature regulation. Maintaining relative humidity between 45% and 55% is generally recommended to prevent clamminess, condensation, and musty odors.