Air Infiltration & Building Envelope Pressurization: The 0.30 CFM Benchmark

## The Mechanics of Air Infiltration in Residential Buildings Air leakage accounts for up to 40% of the heating and cooling load in older American homes. When wind blows against an exterior facade, it creates positive pressure on the windward side and negative pressure (suction) on the leeward side, forcing air through microscopic gaps in window assemblies. ### The Stack Effect in Winter: In multi-story homes, warm indoor air naturally rises and escapes through attic bypasses and upper-floor vents. This creates a low-pressure vacuum on the lower floors that sucks freezing outdoor air through worn-out lower-level window weatherstripping. ### Laboratory Air Leakage Testing (ASTM E283): Windows are tested in pressurized chambers at a pressure differential of 75 Pascals (equivalent to a 25 mph wind): - **Old Wood/Aluminum Windows:** 0.50 to 1.50 cfm/sq ft (drafty, whistling sashes). - **Standard New Windows:** $\le 0.30$ cfm/sq ft (industry code baseline). - **ServiceFind Windows Pro High-Performance Units:** $\le 0.02$ to $0.05$ cfm/sq ft (virtually airtight). Seal your home envelope with ServiceFind Windows Pro. Call for a **Fair Quote**.