A project team is planning a new office building in a cold climate.

Infiltration is uncontrolled outdoor-air movement through cracks, joints, penetrations, gaps, doors, windows, and discontinuities in the building envelope. Sealing these leakage paths directly reduces cold-air entry during winter and conditioned-air loss throughout the year. The project should establish a continuous air barrier, coordinate transitions between assemblies, seal service penetrations, specify effective door and window interfaces, and verify performance through envelope inspection or whole-building air-leakage testing. Additional insulation reduces conductive heat transfer but does not stop air moving through unsealed gaps. Low-emissivity glazing reduces radiant and conductive window heat transfer, but leakage can still occur around poorly sealed frames. Air sealing is therefore the most direct strategy for reducing infiltration-related peak heating loads, energy consumption, drafts, and condensation risks.