"Most Americans spend 90% of their time indoors. The air inside can be 2 to 5 times more polluted than outdoor air — and your HVAC system is either the solution or part of the problem." — U.S. Environmental Protection Agency
Building science doesn't recommend one silver-bullet product — it recommends a stack. Here are the four layers that work together, in priority order.
HEPA causes pressure drop, frozen coils, and compressor damage. MERV 13 is the building science sweet spot: captures PM2.5 and fine particles linked to cardiovascular disease without strangling airflow. Use pleated MERV 13, change every 60–90 days — not 90–120 as the box says. If your system is pre-2010, confirm static pressure tolerance with your tech.
TARGET: Pleated MERV 13 · Changed every 60–90 days · No fiberglassAbove 60% RH: mold grows, dust mites multiply, and structural damage begins. Below 30%: airways dry out, viruses spread more easily, wood warps. A whole-home dehumidifier or humidifier wired into your HVAC is set-and-forget. Standalone units work but need emptying — a $15 hygrometer checked weekly is your minimum investment.
TARGET: 35–50% RH year-round · Non-negotiable in FL, SE, Gulf CoastModern homes are sealed tight — great for energy, dangerous for air. Without fresh air exchange, CO2 builds, VOCs concentrate, and stale air causes fatigue. Per ASHRAE 62.2, homes need a minimum 0.35 air changes per hour. Energy Recovery Ventilators exchange stale air with fresh outdoor air while recovering 70–80% of conditioned energy.
TARGET: 0.35 ACH minimum · CO2 below 1,000 PPM · ERV for humid climatesMost builder-grade bath fans are decorative. They're quiet because silence sold better than performance for 30 years. Per HVI and ASHRAE 62.2: minimum 1 CFM per sq ft or 50 CFM for bathrooms — whichever is greater. Run 20 minutes post-shower with a timer switch. Kitchen range hoods need 400+ CFM to clear cooking pollutants at the source.
TARGET: 80–110 CFM bath fans · 400+ CFM kitchen range hoodThe Keep Your Air Healthy guide translates these four building science principles into a prioritized homeowner action plan — with product categories, targets, and what to ask your HVAC tech.
These are product categories that building science supports — not brand endorsements. Buy based on your system size, climate, and budget. Ask your HVAC tech to verify compatibility.
The ComfortHomeAI Prompt Guide gives you 40 copy-paste prompts engineered around real contractor playbooks. Audit a quote, diagnose an air quality problem, build a maintenance calendar — without a $150/hr consultant.
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