What Does it Take to “See” Air Leakage Through a Building Envelope?

Unwanted air leakage in buildings can cause health and comfort issues for the building occupants and contribute to rot and mold growth in building materials. Leakage also contributes to unnecessary energy consumption, ~4 quads (1172 TWh) per year in the buildings sector in the United States. Finding and repairing leaks through the building envelope can improve the energy efficiency, comfort, air quality, and moisture durability of the building stock. Typical methods of locating air leakage, such as infrared imaging or smoke tracing, rely on concurrent blower door operation, which also measures the total leakage rate of the building. These methods can be disruptive to occupants and cannot measure the contribution of individual leaks to prioritize sealing efforts. Oak Ridge National Laboratory is working on a refraction-based fluid flow imaging technique that can measure the leakage rate of individual leaks from the inside or outside of the building. The working principle of this technique is based on the refraction of light caused by the exfiltration as there is a small difference in density between the exfiltration and ambient air. We discuss the operation of the air leak detector and key variables that affect its performance. We also present preliminary results showing the visualization capability of this new air leak detector under different conditions. Experiments were completed with different claddings, air temperatures, and lighting conditions.