Bathroom Fan & Dryer Vent Exhausts: How Improper Roof Venting Leads to Moisture, Odors & Leaks
Bathroom fans and dryer vents are designed to exhaust warm, moist air outside. This is important for preventing the bathroom and laundry room from getting overly humid, which could otherwise lead to issues like condensation, water damage, and mold growth. These exhaust vents normally stick up through the roof to ensure the moisture gets vented outside and not into the attic. However, the vent pipes in some older homes do just lead to the attic or have other venting issues, such as the pipes not being insulated. When warm, moisture-laden air is released into cold attic spaces, it can damage insulation, roof framing, and the roof deck. Proper roof venting is essential to protect the attic and the roofing system.
Why Exhaust Venting Mistakes Show Up in Winter
In places like Virginia, Maryland, and DC that experience cold winters, it’s crucial that the bathroom vent and dryer vent through the roof blow the warm, moist air outside. Attics always get quite cold in the winter because outdoor air flows in through the soffit, gable, and ridge vents. Improper venting leads to the moisture in the warm air condensing on all of the cold surfaces, which can create major attic moisture problems, including mold growth, odors, and structural damage.
Another concern with improper dryer and bathroom fan venting is that it causes the attic and roof deck to heat up whenever the exhaust fan or dryer is running. If there’s snow on the roof and the deck is warmer than the outdoor air, ice dams can form on the roof and potentially result in significant damage to the shingles and gutters or lead to the roof leaking.
Common Roof Venting Problems That Lead to Moisture and Odors
The two most common issues are fans being vented into the attic or not being fully encased in insulation. A bathroom fan or dryer that exhausts moisture into the attic is always the biggest concern, as it leads to significant condensation issues in winter. In colder climates, it’s also essential that the vent pipes in the attic are insulated. If they’re not, the pipes will get cold enough that condensation forms inside them whenever the fan or dryer is running. This often results in water leaking out of the seams in the pipe and damaging the insulation on the attic floor and the drywall on the ceiling near the pipe.
Some vents use flexible ductwork instead of rigid metal pipe. The concern with flexible ductwork is that it’s quite easy to tear it or put a hole in it, which then allows moisture to escape. You can also encounter an issue where the pipe or duct comes loose, resulting in all of the moist air being vented directly into the attic.
The part of the vent pipe on the roof has a metal damper in it that blocks cold air from flowing down through the pipe. When the fan or dryer is running, the force of the air pushes the damper open to allow the air to escape. The outside damper can sometimes get stuck, which also leads to condensation forming in the duct in the attic.
Another serious concern is a roof vent leak where water seeps in around the vent pipe. This can happen because the metal flashing around the vent pipe is missing, wasn’t properly installed or needs to be resealed.
When an Inspection Is the Right Next Step
Improper roof ventilation is definitely not something you should ignore. One fairly sure sign of poor or improper ventilation is a moldy attic smell or visible mold growth on wood or insulation. Water stains on the ceiling around the bathroom fan or kitchen exhaust fan also indicate that condensation keeps forming inside the vent pipe. By scheduling an inspection as soon as you suspect any type of problem, you can avoid costly damage or needing to pay for professional mold remediation. The biggest concern with waiting to fix any type of ventilation issue is moisture damaging the roof deck and greatly shortening the life of the roof.
Protect Your Attic and Roof System With Proper Exhaust Venting
With more than 45 years of experience, R&K Roofing is the trusted choice for roof repair in Virginia, Maryland and the DC area. Our expert team can identify and fix any roof ventilation issues or any other problems. We work with residential and commercial roofs, and we offer free estimates on all of our services. To schedule a roof ventilation inspection for your home or business, contact us today.
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