Is Your Bathroom Properly Ventilated?

bath 02.11.15

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We've seen it probably more than 100 times. In an attic, the bath fan discharges directly into a pile of insulation. You would be surprised that it's more common than many people realize! If you don't know the condition of yours, it's worth a quick investigation. So, what are the indicators of a properly ventilated bathroom? Here are a few tips.

1. Select the correct size bath fan. Many have a square footage chart included at time of purchase, but there are tables available online as well, such as this one from HVI:

2. Ensure adequate make up air can reach the fan. As pictured, allow a minimum of 3/4" clearance under the door, and even more if possible. Use caution, however, that hollow doors only have a small solid rail at the bottom which could limit the cut off.

3. Always terminate the ductwork to the home exterior. In the photo, the duct is attached to a pre-cut galvanized sheet, and connected

  • This preset bath fan timer is a great solution for ensuring the bath fan runs for an adequate amount of time. The 30 minute preset is typically used for showering.
  • The duct shown is terminated to the exterior, which is required by code in most areas. Minimize the twists, turns, and fittings used in the ductwork for the best airflow.
  • The "paper test" in action.
  • Ensure proper make up air, because that is usually the only spot where it is drawn from during a shower.
  • Building Moxie
    Building Moxie Baltimore, MD
    thanks Paul @ Hamtil Construction LLC it did get me thinking ... excellent tip on looking at swapping out only the motor. I'll look into it. cheers my friend.
  • Hamtil Construction LLC
    Hamtil Construction LLC Saint Louis, MO
    Good tips Vicki and thanks for adding to the discussion. The smoke test for fans is a good one, and I would say is more reliable, especially when checking the make up air under
  • Hamtil Construction LLC
    Hamtil Construction LLC Saint Louis, MO
    Cherie Dunkel-Hoysock That is a new one for me. You mean that you share a sewer lateral in the yard out to the main sewer line? Is it undersized? Have you had a drain
  • Vicki
    Vicki Smyrna, GA
    they from weatherization used incense to test but paper is very good idea. they put duct from bathroom ceiling toward to eave instead of to the attic.
  • Hamtil Construction LLC
    Hamtil Construction LLC Saint Louis, MO
    Sharron W Thanks for the feedback! Interestingly, building code in many places states that you can forgo the bath fan if there is fresh air in the room, i.e. from a window, and
  • Vicki
    Vicki Smyrna, GA
    ty for sharing. we learned from weatherization that it should go out of the house, not to the attic. we have timer to turn one hour before we go to shower. we are thinking to have humidity sensor bathroom fan exhausted to turn on by itself whenever there
  • Hamtil Construction LLC
    Hamtil Construction LLC Saint Louis, MO
    Barbara Kalyta Sorry to hear about the issue. To me, it sounds as though you may have a plumbing vent issue, which is separate from a bathroom fan vent. While a vent fan may
  • Hamtil Construction LLC
    Hamtil Construction LLC Saint Louis, MO
    Thanks for the feedback Building Moxie, and I have read that post by Sean, which is a good one on the topic!
  • Hamtil Construction LLC
    Hamtil Construction LLC Saint Louis, MO
    Well, it's not really a good idea to have it discharging into the attic. Code requirements for us dictate that it must terminate to the exterior, and that is the ideal way to do
  • Erin H
    Erin H Las Vegas, NV
    I learned that trick from Mike Holmes and none of my bathrooms are properly ventilated. They don't really take pride in the housebuilding anymore. The developers just want to crank out as many houses as possible to make a bunch of money. My house is less
  • Peter Klarman
    Peter Klarman Bayside, NY
    When my first floor and basement bathrooms were renovated the first task was to vent the first through the roof and the basement through the brick wall.
  • Cherie Dunkel-Hoysock
    Cherie Dunkel-Hoysock Pottsville, PA
    I am currently remodeling my home that is attached to my neighbors. I do not have ventilation and plan on installing one. However, we share a sewer and everytime my neighbors flush their toilet I lose my water in my toilet and it always smells like
  • Sharron W
    Sharron W Memphis, TN
    Hamtil Construction LLC This is SUCH great information! Our house is so old and I am confident that the bathroom fan is not properly vented....the Master Bath doesn't
  • .
    . Albert, OK
    Thanks for the great info Paul.
  • Barbara Kalyta
    My powder room is not vented and usually smells horrible. The toilet also is constantly plugged up. Nobody should have to use a plunger as often as I do. I have no idea of what needs to be done to fix it. The room is in a former carport. Over the packed
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