In addition to chimneys, ventilation is needed for kitchens and bathrooms to remove and/or filter exhaust from within your home. Ideally, ventilation would always be to the exterior so that exhaust gases and moisture could be removed from the house entirely. However, this is often not the case. In this post, we’ll look at a common but prohibited method for ventilation that should be corrected if it exists in your home.
Kitchen ranges are often vented with recirculating ventilation from an above-range microwave or vent hood. These systems are very common and do a decent job, but as mentioned previously, venting to the exterior is always preferred when possible. Bathroom ventilation is where the defect typically comes into play, and that’s the focus of this article.
Unlike kitchen ventilation, which exists to remove and filter cooking gases, moisture and residue, bathroom ventilation serves the primary purpose of removing moisture. The exhaust piping for bathroom vent fans (mechanical ventilation) is routed into the attic space. Unfortunately, many contractors become lazy and stop there. The vent piping should extend through the roof and to the exterior so that the moisture is removed from the home entirely.
Of course, continuing the vent piping through the roof adds a whole new set of unwanted challenges for the contractor. It requires him or her to cut a hole through the roof decking, run the extra piping, and then seal and reshingle around the penetration. Not only that, but the duct should also be insulated to prevent condensation from forming and causing moisture problems. As you can imagine, this extra work is not exactly a dream job for contractors, and many simply leave the vent piping open in the attic if the attic isn’t finished. They assume that homeowners are too ignorant to know that this is improper and that it will really be fine (and go unnoticed).
As you can imagine, though, this simpler method is anything but “fine.” Rather than moisture exhausting outdoors as it should, it exhausts directly into the attic space where it contributes to high humidity, moisture buildup, and eventually mold or even rotten wood framing members. In addition, the indoor air quality inside the home will often be diminished without the homeowner even realizing it. It can also saturate insulation making it less effective at performing its job of preventing air movement to reduce the transfer of heat. Granted, it may take a while for these problems to become significant and noticeable, but they will eventually become worse and worse over time if the ventilation is not fixed.
If you have an unfinished attic and a vent fan in your bathroom(s), you should check your attic to make sure the vent ducts are all exiting through the roof. If you notice any that are terminating directly into the attic space, you should contact a qualified contractor to correct the problem by properly extending the vent piping through the roof, insulating it, and sealing the penetration(s) well. This will improve your indoor air quality, the performance of your insulation and energy efficiency, and prevent unwanted mold and other moisture related problems.
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