04/11/2025
A problem we are seeing more and more, mold around bathroom ceiling exhaust fans in newer homes. For the last decade, Eastern NC climate has been trending more humid for a longer duration throughout the year. Poor quality (leaky) dampers and improperly balanced HVAC systems without ERVs have been allowing hot humid air to flow inside the home and condense on bathroom ceilings. This leads to rampant and recurring mold growth. This is our current solution without adding an ERV (better solution). We first tape the fan housing to the ceiling, so no foam falls through onto the grill. Then we fabricate a box around the housing from polyiso RFB and tape the seams and joints, including a lid. After that we use expanding foam to air seal the entire housing, and the housing to the ceiling. The trick is air sealing the housing itself, and the housing to the ceiling, while also insulating. We then add an addition inline back flow damper to the exhaust duct, and ensure the duct runs to the exterior. This is a cost effective way to solve the problem. A better solution would be to install an ERV, to provide ventilation for the bathrooms, and positively pressurize the home to prevent back flow through any individual exhausts. An ERV, energy recovery ventilators are great as they scavenge some energy from the conditioned exhaust air, and temper the incoming make up fresh air. However this is not the solution for all homes and all customers. “Never make a home suck. “. Air Quality Control has been providing customers with innovative solutions for indoor air quality problems since 1999.
