Drafty exhaust fan in bathroom
specialgranny
10 years ago
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Comments (6)
bpchiil
10 years agoklem1
10 years agoRelated Discussions
What Size Exhaust Fan for Bathroom
Comments (3)Building Code Requirement: Minimum ventilation for the bathroom is to be a window of at least 3 sq. ft. of which 50% is operable, or a mechanical ventilation system of at least 50 cubic feet per minute (cfm) ducted to the outside. (IRC R 303.3, IRC M 1506.3) Heating Ventilation Institute (HVI) Recommendations: HVI is an industry association of heating and air conditioning product manufacturers that, among other things, tests and certifies ventilation products and publishes consumer guides on ventilation issues. These are the HVI recommendations for venting bathrooms: Small Bathrooms: HVI recommends that in small bathrooms, up to 100 square feet of floor space, the exhaust fan be sized to provide a ventilation rate of 1 cfm per square foot (about eight air changers per hour). This usually results in a ventilation requirement of less than 50 cfm, so the code minimum fan size must be used. Example 1: The bathroom is 5' x 9' (with 8' ceilings). Multiply 5x9 = bathroom area of 45 sq. ft. At 1 cfm per square foot the minimum recommendation is a fan rated at 45 cfm. This is less than the code minimum 50 cfm, which must be used. Medium and Large Bathrooms: For bathrooms larger than 100 square feet in area, HVI recommends a ventilation rate based on the number and type of fixtures present, according to the following table: Toilet 50 cfm Shower 50 cfm Bathtub 50 cfm Tub/Shower Combination 50 cfm Whirlpool Tub 100 cfm To calculate the minimum fan rating, add the cfm for each fixture in the room to arrive at a total cfm. Example 2: The bathroom is 20'x12'. There is a tub, a separate shower enclosure and a toilet. Toilet 50 cfm Shower 50 cfm Bathtub 50 cfm Minimum Fan Rating 150 cfm Toilet Compartment: If a toilet is in an enclosed stall with a door, then the toilet enclosure is considered by most code authorities to be a separate room. Likewise, if a shower is enclosed right to the ceiling, it will be considered a separate room. These guidelines recommend a separate mechanical exhaust system for "each enclosure", which means a fully enclosed toilet or shower must have its own exhaust fan separate from that of the rest of the bathroom. In most localities, this is also the building code requirement. A steam shower always needs its own ventilation. Strictly follow the manufacturer's recommendation for venting a steam shower. Otherwise you will have mold growing in places you would not think mold could grow. Example 3: The bathroom is 15'x15'. There is a tub, a separate, fully enclosed, shower and a fully enclosed toilet in a stall with a door. The fully enclosed toilet and fully enclosed shower should have their own exhaust fans rated at 50 cfm each. The bathroom fan will exhaust only the bathtub and should also be rated at the code minimum 50 cfm. How Long to Ventilate: When house air is exhausted to the outside, heat goes with it, meaning that your furnace has to work harder to make up for the lost heat. You want to exhaust moist air to reduce the risk of mold and mildew, but once the moist air is gone, you want to stop ventilating. HVI recommends that the fan be left on for a minimum of 20 minutes after use of the bathroom. A timer is a good solution, allowing the fan to turn off automatically at the proper time. There are also fans on the market now that sense the level of humidity in the air and automatically turn on when it is too high, and turn off when it is back to normal. Unfortunately, there is no fan that senses odor, so a manual switch is still necessary....See MoreBathroom exhaust fan installed in the floor, anyone?
Comments (13)Babka: ha. they (fixtures) are vented to the space above, (which is under the stairs), not to the outside - which is against the code, I know that much. I guess they (whoever added this bath) ran into the same problem with venting fixtures as we are facing trying to figure how to vent the exhaust fan. and maybe that's why there is no exhaust fan to start with. The bathroom is under the staircase whichi s in the middle of the house, and there is space directly above it because the ceiling is short. But then the ceiling height changes as you go to any neighboring room (the rest of the house around has much higher ceilings). Basically, you can put the duct vertically through the ceiling above the bathroom, but then as you turn it 90 degrees towards in the direction of any outside wall, it would have to come out through the wall of any room around, not in the ceiling above the rooms. And if you try to go higher with the duct so that the turn is at the level of the over-the-ceiling space for these rooms, then the duct would have to come out through the staircase! Hard to explain, but I hope you go the picture. Also, even if we could somehow get the duct to the space over the ceiling of any adjacent wall, then we still can't open up that high ceiling to run the duct further because it has some fancy beams and moldings (house is over 100years old) so we cannot touch the ceiling. That's why I wrote "absolutely no way" for the ceiling route Unless, as somebody above suggested, we place the fan in the ceiling, but run the duct through the wall down to under the house (actually through the under-the-stailrcase part as the stairs go down). But as far as I understand that comment, we will have to install some inline fans in the duct to keep the air moving down......See Moreinsulating bathroom exhaust fan
Comments (1)1. Avoid using the flexible, "accordion-style" pipe if at all possible: since it doesn't have smooth walls it can accumulate dust and mold more easily. 2. For insulation of the pipe, get HVAC foil tape and use it to seal all the joints; it's about the same dimensions as regular duct tape, but more tenacious and won't deteriorate over time. After you have sealed all the joints, you can wrap it with fiberglass batting and tape it to stay in place around the pipe. When I've done this, I've not only taped the seam that runs parallel to the pipe, I've put a wrap of tape all around the circumference every foot or so. Taping the insulation on will be easier and you will get a better result if you have foil-faced or paper faced batting with this layer on the outside. P.S: I've never tried spray foam, but it could be messy, and would be a pain if you ever needed to get at the ductwork....See MoreVertically-ducted Bathroom Exhaust Fan
Comments (5)Photos? I prefer a inline fan but if you have no attic get the largest and quietest fan you can. Then you get a foot of rigid duct, an adjustable elbow, and another short length of duct to go through the roof. No need to go straight up....See Morespecialgranny
10 years agoUser
10 years agoLee Helwig
2 years ago
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