Exhaust Roof Vent Clearance 1” or 2” tall collar is recommended for all climate zones 1 - 8.
Not less than 5 feet (1524 mm) of horizontal clearance from the outlet (fan housing) to a combustible structure. A vertical separation of 3 feet (914 mm) below an exhaust outlet for air intakes within 10 feet (3048 mm) of the exhaust outlet.
Many ceiling mounted fans will require at least 220mm of space (some more and some less, this is a generalisation). To be sure measure the cavity space and cross reference this with the information we have on each product listing. If you have a large roofspace above the room then this is not a concern!
Chapter 15 of the International Residential Code (IRC) requires bathrooms and toilet rooms to have a minimum local exhaust capacity of 50 cfm intermittent or 20 cfm continuous.
Considering that the exhaust from a dwelling unit is not considered to be hazardous or noxious and is of low volume, the 3-foot (914 mm) separation from windows is deemed to be reasonable.
For best results in removing moisture, the exhaust fan should be positioned as close as possible to the source of the moisture and away from any source of replacement air. Placing the exhaust away from doors or windows creates cross-ventilation, ensuring that it can effectively service the entire room.
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.
One Foot In, One Foot Out – Ideally, you should place a bathroom fan in the ceiling about 1 foot from the shower and between the shower and the door.
For better performance, duct runs should be as straight as possible. If a bend is necessary, 2 to 3 feet of straight duct should be allowed to run from the fan exhaust port to the first elbow in the duct run.
To ensure that air will circulate efficiently, your ceiling fan blades should have approximately 30 inches of clearance from the walls.
A mechanical draft venting system, excluding direct-vent appliances, shall terminate at least 4 feet (1219 mm) below, 4 feet (1219 mm) horizontally from, or 1 foot (305 mm) above any door, operable window or gravity air inlet into any building.
The building code requires that you allow for a 2.1m clearance between the fan's blade and the floor. We suggest installing the fan so that the blade sits between 2.1 and 2.4 metres above the ground, but this suggestion might not suit everyone.
Exhaust Fan: Primarily focuses on removing moisture and odours, aiding in humidity control and air quality improvement in targeted areas. Ventilation fan: Helps regulate temperature by drawing in cooler outdoor air, reducing indoor temperatures, and aiding in overall humidity control.
So how much space does an air return vent need to work properly? Home Inspection Insider explains that an air return vent needs 6-12 inches of space in front of it, and recommends that you do not put large, bulky furniture like couches and bookshelves in front of an air return vent.
To adjust the CFM, you can change the speed of the blower or alter the ductwork size. Increasing the blower speed won't have much effect if a room's duct is too narrow. A 12' x 12' foot room is 144 square feet. You generally need at least 1 CFM per square foot, meaning that room's duct should have a 144 CFM capacity.
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.
However, we recommend never going more than 10-20% large than the minimum CFM. We also recommend not going under the minimum CFM as the airflow exhaust fan will be underpowered and may not adequately remove the moisture needed.
The location should be between two wall studs and within 6 feet of the vent fan. Take a couple of reference measurements so that you can locate the spot from outside—from a nearby window, soffit, or other feature you can access from outdoors.
New NEC® Section 422.18(B) states that metal parts of ceiling-suspended (paddle) fans in bathrooms and shower spaces shall not be located within a zone measured 3 feet horizontally and 8 feet vertically from the top of the bathtub rim or shower stall threshold.
Flexible duct is acceptable for a bathroom exhaust fan. Approved by building codes-Chapter 15 of the International Residential Code (IRC), it is available in PVC, PVC coated aluminum, aluminum and insulated aluminum.
Seal holes in the fan housing with caulk, sealing putty, or metal tape. Install the fan then seal around the fan with caulk or canned spray foam. Seal the exhaust duct to the fan box with approved metal tape or mastic. Seal around the exterior fan duct vent with caulk or a pre-made exterior wall gasket.
When the fan is in the center of the bathroom, it actually drags the moisture from the shower across the room rather than venting it straight out and away. To prevent this, bathroom fans should be placed in the shower or just outside of the shower to eliminate moisture at the source.
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.
Wall Mounted Bathroom Exhaust Fans
You can attach a wall mounted bathroom exhaust fan to an external wall in a bathroom. This type of fan pulls the air out of the bathroom, through the ducting and outside via the external wall of your home.