Heritage Restoration, Inc.

Bathroom Venting

The are many common house problems both large and small caused by poor renovation and construction methods.  Some of the bigger problems are flashing, poor drainage, incorrect insulation, or substandard framing and finishes.  The smaller issues are nuisances that people may not notice at first, but can turn into rather large problems later.  The most common nuisance turned problem for new and old houses is proper ventilation.


A friend was recently telling me that her father flipped his lid over a discovery in his 10 year-old house.  He is an out of state builder who hired a local contractor to build a house, so he thought he was on top of them.  It is a nice enough house, with a front porch, central stair with an open first floor plan, and an attached garage.  The house was vinyl sided, with vinyl railings and a wood deck.   The house is starting to wear and parts are starting to fail.  Pretty standard stuff.


Recently, the bathroom fan stopped working.  He decided to take out the unit and replace it.  All he had to do was buy a new unit, disconnect the old one, and “pop” in the new one.  Well, then he discovered the horror that made his blood boil: the fan was not connected to the outside.   By the words coming from the bathroom, my friend thought he got hurt.  Nope, this was bigger.  Why?  Assuming you have proper bathroom ventilation and using it will cause more moisture damage than not having any fan at all.


A shower can create from a cup to a pint of water vapor.  This water vapor has to be managed, or else you can have an unhealthy space or, worse, house.  A healthy house keeps the relative humidity either equal to the exterior, or less by dehumidification, like dehumidifiers or air conditioners.  A good relative humidity range is between 25% and 60%.  While scientists and allergy sufferers beg to differ, the range is really based on your health and the building’s health.  Too low and you get nosebleeds, too wet and the building gets mold.  So when a bathroom does not vent properly, now you have concentrated moisture hitting wood surfaces, or even worse, fibrous insulation.  Say hello to mold.


Installing a fan is relatively easy, right?  You fasten the fan to your ceiling joists, run the power and voilà, it works.   Well, you just finished the easy part, which is the part where many walk away.  Unless you are exhausting into a well-ventilated area with no insulation, you must vent the fan out of the house.  Would you ever not duct a stove hood (smelly), dryer vent (hot, wet and linty), or radon mitigation system (dangerous)?  So why treat the bathroom different?


The best method of install is a hard pipe duct.  Yes, a bathroom vent can be a flexible vinyl duct, or aluminum flex pipe, but I cannot help but think about all of those nooks and crannies getting trapped moisture and growing mold.  The flexible aluminum tears easy, and the vinyl breaks down over time.  When installing the duct, pay attention to the directions.  There are limits to the length of pipe and how many bends to get the most out of the fan.  Use foil faced duct tape on every seam or bend.  The gray duct tape that everyone has is great for everything BUT ductwork.  It dries, looses its stick and falls apart over time.  Ducts going through an unconditioned space should be wrapped with insulation.


The exterior vent can be either installed on a roof or on a wall.  It is essential to buy a quality vent.  A good vent has a sturdy flap, well designed not to fall off during installation, which means it will fall off later and allow cold air to rush into your house.  To cut the hole, you will need a properly sized hole saw (easier), or if your good, a reciprocating demo saw or jig saw (harder).  The vent has side tabs that are designed to go under the siding or roof, not over it and caulked.  These can be installed without caulk when they are installed right.  You may need to remove some siding or roofing to get it in there.


Like many things, it is harder and takes more time to do it right.  So when someone gives you a quote for $600 to install a fan and another gives you a quote for $300, you will get a complete job either way, just one is right, and the other is not.  If it was easy to do it right, anyone could do it.



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