Indoor Climate & Fixtures

Residential HVAC furnace air filters standardize nominal dimensions (16×20×1", 16×25×1", 20×20×1", 20×25×1", 20×25×4") that measure 0.5 inches smaller in actual size, rated on the ASHRAE 52.2 MERV scale from MERV 1 to 16.

Ceiling fan blade spans standardize to room square footage: 36" for small rooms (<75 sq ft), 42–44" for bedrooms (75–144 sq ft), 52–54" for living rooms (144–225 sq ft), and 60"+ for great rooms, requiring a minimum 7-foot blade floor clearance.

Window curtain panels standardize lengths across 63" (sill length), 84" (8-foot ceiling floor length), 96" (9-foot ceiling floor length), 108" (10-foot ceiling), and 120" (two-story), with a 1.5× to 2× fullness width multiplier.

Domestic light bulb bases standardize screw (Edison) and pin configurations. The E26 (26 mm) base serves as the standard medium screw in 120V North America, E27 (27 mm) in 230V Europe, E12 (12 mm) for candelabras, and GU10 for 120V/230V twist-lock track spotlights.