Air sealing is the process of identifying and closing unintended air leaks in building envelopes and HVAC systems to reduce energy loss and improve indoor comfort. Common leak locations include ductwork connections, wall penetrations, window frames, and foundation cracks. Sealing these gaps prevents conditioned air from escaping and unconditioned air from entering.
Methods and Materials
Technicians use duct mastic, spray foam, weatherstripping, and caulking to seal air leaks. Blower door testing identifies leakage rates in air changes per hour (ACH). Most energy codes target 3 to 7 ACH50 for residential buildings. Sealing ductwork can reduce leakage from 20-30% to below 5% in well-executed projects.
Energy and Comfort Benefits
Properly sealed homes reduce heating and cooling costs by 10-20% annually. Air sealing prevents drafts, improves temperature consistency between rooms, and reduces infiltration of outdoor pollutants and allergens. Sealing also enhances HVAC system performance by ensuring designed airflow reaches intended spaces rather than escaping through gaps.