If the exhaust fan has two ducting collar size options (typically 4” and 6”), always use the larger duct size if possible. The exhaust fan should be located at the highest point in the bathroom (typically ceiling) and located near (within ~5 feet) the shower.
Some fans will work in either a ceiling- or wall-mount installation. Check the size of the exhaust port on the fan to make sure it fits your duct work. A diameter of 4 inches is common for exhaust ducts, but some high-CFM fans fit a 6-inch-diameter duct.
When you operate the fan, typically air is pulled from the bathroom through a 4 inch exhaust pipe.
Are bathroom extractor fans a standard size? Domestic extractor fans tend to come in two sizes: 4 inch/100mm and 6 inch/150mm. This size refers to the size of the impeller (the revolving part inside the extractor fan that sucks the air out).
If the exhaust fan has two ducting collar size options (typically 4” and 6”), always use the larger duct size if possible. The exhaust fan should be located at the highest point in the bathroom (typically ceiling) and located near (within ~5 feet) the shower.
Fan Size: Select a 4-inch fan for smaller bathrooms and a 6-inch fan for larger spaces. Safety Zones: Ensure the fan is suitable for the bathroom's zone and has the right IP rating.
Section M1507.
This section notes that air exhaust from the bathroom must be sent outdoors, not indoors, to the same residence or indoors to any other dwelling unit. It cannot move air to a crawlspace or attic.
For medium-sized bathrooms, use 80 to 99 CFM bath fans. For large bathrooms that are over 100 square feet but under 150 square feet, use over 100 CFM bath fans. For extra-large bathrooms, add 50 CFM for every toilet, 50 CFM for every bathtub or shower and 100 CFM for a jetted bathtub.
Well, you can't! You'd often blow air from one bathroom into the other, and local building inspectors wouldn't approve it. But while you can't have two fans with one vent, you can make one fan and one vent serve two bathrooms. This setup requires an in-line exhaust fan.
Use Solid Ducting Wherever You Can
The smooth sides of solid ducting provide a huge increase in performance: Smooth sides allow the air to travel through the ducting without being impeded by 'ribs' and 'imperfections' associated with flexible duct.
Grilles and vents come in different sizes. A standard floor vent size has a duct opening of 4 inches x 10 inches.
Draw a mark on the bathroom ceiling where you'd like to install the vent fan. For optimum performance, locate it between the shower and the toilet. Use an extra-long, 3/8-inch-diameter spade bit to bore a reference hole through the ceiling and into the attic.
The most common types ducts that can be used for a bathroom exhaust fan installation are rigid ducting, semi-rigid ducting, flexible ducting or a rigid duct and flexible duct combination.
The required size of the drain shall be determined in accordance with Chapter 30. Vent pipes shall be not less than 11/4 inches (32 mm) in diameter. Vents exceeding 40 feet (12 192 mm) in developed length shall be increased by one nominal pipe size for the entire developed length of the vent pipe.
Is it safe to run an exhaust fan all night? The short answer is: yes. It is safe to run a bathroom exhaust fan all night.
Yes, the toilet and sink can share the same vent, as can the shower. It's common to have one main vent pipe for multiple fixtures, although you might need a larger pipe. You should check with local building and plumbing codes to confirm you'll have adequate piping for your home.
Sec. 62. (a) Main Vent. The drain piping for each toilet shall be vented by a one and one-half inch (1 1/2") minimum diameter vent connected to the main drain by one of the following methods: (1) A one and one-half inch (1 1/2") diameter (min.)
When sizing a vent fan, a factor to consider is duct size and length. Most 50 CFM fans will run well with a 4-inch round duct. But as you get up into the higher CFM fans, duct size will have to be increased to a 5- or 6-inch round duct.
To fulfill the local exhaust airflow requirements of ASHRAE 62.2 (2010) and the International Residential Code (IRC 2021, Section M1507), bathroom fans should have a mechanical exhaust capacity of ≥ 50 cfm for intermittent operation or ≥ 20 cfm of ventilation when operated continuously.
Vent pipes must be installed so they stay dry. This means that they should emerge from the top of the drainpipe, either straight vertically or at no less than a 45-degree angle from horizontal, so that water cannot back up into them.
While most bathroom fans have a 100mm spigot (the diameter of the air outlet on the back), kitchen fans tend to have a 150mm diameter spigot.
The extraction rate you need for your bathroom will depend on the room's size. However, building regulations state that the minimum fan extraction rate your bathroom should have is 50 m^3/hr (or 15 l/s) if the room doesn't have an openable window, so do ensure you at least meet this level.