Uncontrolled airflow (i.e. leakage) through the envelope can be the major source of heat loss and can lead to other problems. Since warm air can carry large amounts of water vapour, airflow is also the main means by which moisture is carried into the envelope.
Controlling airflow protects building materials from moisture damage, improves comfort and makes for a cleaner, healthier, safer and quieter home. Controlling airflow prevents uncontrolled air leakage through the building envelope, provides for fresh air supply and the exhaust of stale air, and provides draft and combustion air for fuel-burning appliances.
Airflow 2.4.1 Crack
An air barrier blocks airflow through the building envelope. It reduces heat loss by preventing air from passing in and out through the envelope and protects the insulation and structure from moisture damage. The air barrier, when located on the exterior, may also act as part of the drainage plane. Standard building materials, such as exterior sheathing, building paper and house wrap, act as the air barrier.
First, most older houses are so loosely built that, even after extensive air-leakage control work, enough air will still come in to provide ventilation. Second, the air barrier is just the first step in the control of airflow.
Cold outdoor air cannot carry much water vapour. In poorly air sealed homes, uncontrolled airflow brings colder, drier air indoors and forces the warm, moist air out through openings in the upper walls and attic. The moist air condenses and causes mould and structural damage. 2ff7e9595c
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