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Proper Exhaust Fan Ventilation

Proper Exhaust Fan Ventilation

A few weeks ago we discussed the importance of properly insulated vent ducts to prevent mold and water damage to your attic due to condensation. Another common mistake that can lead to sever roof decking, support beam and ceiling rot and mold is improper exhaust fan ventilation.

Problem with bathroom exhaust fanAttic damage

Pictured to the right is a common mistake: this bathroom fan was vented directly into the attic blowing moisture, causing mold growth and plywood rot. Plywood is made of thin sheets of wood veneer (or plies) arranged in cross-laminated layers to form a panel. OSB is made with
rectangular shaped wood strands cross-oriented in layers, and is the most popular alternative to plywood. Regardless, both products will delaminate, buckle and rot in the presence of high moisture content.

Proper exhaust fan ventilation solution

Properly insulated vent ductsProperly venting your bathroom exhaust fan through the roof is essential for removing moisture from your attic space. This is done by re-routing or installing duct pipe from the fan and then routing it to an exterior vent onto the roof giving an exit for moisture. It is important to note that proper exhaust fan ventilation isn’t enough on its own. It is imperative that insulated flex hose is used to reduce condensation problems.

Upgrading your attic ventilationProper attic air flow

Proper attic ventilation extends the life of your roof and makes your home more comfortable and energy efficient. In the summer, attic temperatures can soar to over 150-degrees Fahrenheit. This makes your home hotter inside and increases the level of energy consumption created by cooling and air-conditioning equipment. Hot, moist air can also create a breeding ground for mold and mildew under your eaves.

Improper ventilation and attic moldAttic Ventilation

Mold can commonly be found growing in attics. Attic mold growths can have a variety of causes. Inadequate ventilation is one of the major contributing factors (particularly to very extensive infestations). Attics that are particularly prone to moisture problems may need to be ventilated with vents that have motorized fans. Regardless, all attics need to breath.


If you suspect that your ventilation system, or duct system, might not be doing its job correctly, call a professional right away. Letting issues like this go can turn a simple clean up job into a major roof replacement job and cost you thousands of dollars. What do you have to lose? Our inspections are FREE. Visit our website to use our online scheduling tool where you can pick your own appointment date and time.

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