The building envelope, walls, roof, windows, doors, and foundation, acts as the barrier between indoor and outdoor conditions and must manage multiple functions simultaneously. Thermal control prevents unwanted heat gain or loss while allowing controlled temperature management. Moisture management controls water vapor movement to prevent condensation and moisture accumulation that leads to mold growth. Air flow regulation manages air exchange rates while preventing uncontrolled infiltration of outdoor pollutants. Pressure balance maintains appropriate pressure relationships between indoor and outdoor spaces. When the envelope fails in any of these functions, indoor environmental quality deteriorates, creating health risks and comfort problems for occupants.