Moisture is a big concern for any client and air leakage is an often overlooked aspect of managing moisture. At Foxhound Inspections, our qualified home inspectors make sure we pin point problematic areas and address them to our clients.
Air flow can transfer moisture vapor through and into building assemblies in amounts 10 to 100 times more than what would typically occur by vapor diffusion. Significant air leaks -- from a bathroom into a cold attic, for example -- can deposit a large amount of moisture vapor on cool surfaces and create condensation and water accumulation that can damage building materials and make some insulation materials ineffective. Without reasonable air-leakage control, the use of vapor diffusion retarders is of limited benefit. Similarly, attempts to pressurize a building in a hot-humid climate to control against the intrusion of outdoor humidity and to depressurize a building in a cold climate are far more effective with a tighter building shell.
Some amount of natural air leakage under the right climate conditions can be a good thing. Old houses naturally breathe, and that can be beneficial. Under ideal conditions that may occur during some periods of the year, it can help to dry the house. Air leakage in the form of intended ventilation in attics and crawlspaces -- outside of the building’s thermal envelope -- is a good way to reduce moisture and is very effective in many climates. Air leakage through the thermal envelope can also allow for uncontrolled natural ventilation of the building for indoor air quality.
However, the benefits of air infiltration through a building’s thermal envelope are either unreliable or risky in many climates. Therefore, dependence on excessive or uncontrolled air leakage through thermal-envelope systems in modern buildings and new construction is generally discouraged. And, in fact, modern building standards and energy codes usually require fairly extensive practices to prevent the uncontrolled leakage of air through a building’s thermal envelope.
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