Are bathrooms required to have exhaust fans?

Do bathroom exhaust fans go outside?

Bathroom vent fans must be vented to the out of doors. Venting this fan into the attic is simply asking for problems. The excessive moisture will cause condensation on the roof members, insulation and eventually cause mold. It is never OK to vent directly into an attic even if the attic itself is vented.

The cause of condensation. Moist indoor air condenses inside a cold, uninsulated duct and water runs down into the fan. Water stains on the ceiling around your bath fan may indicate a leak coming from the vent cap on your roof, but condensation is the more likely culprit.

Installing a bathroom fan obviates the need to install a window. The bathroom fan should pull out at least 50 cubic feet per minute (cfm). Because windows provide light as well as ventilation, if you go the fan-only route you need to install artificial lighting. The exhaust fan must route to the exterior.

In fact, most dryers are essentially acting as exhaust fans when they run because they take air from the room and exhaust it outside. As far as I know no active fan is required by code in laundry rooms. Most laundries vent the dryer outdoors which is sufficient to dissipate humidity from the room.

Each bathroom has its own exhaust fan; each fan vents separately out the roof. If you have two bathrooms that are close together and one has an exhaust fan and the other doesn’t, you might be wondering if you can tie a new exhaust duct into the existing one. You mount a switch in each bathroom.

An effective means of egress in the event of a fire is the reason there are window requirements on the bedroom space. Technically, a bedroom must have two means of egress, so a second door will suffice, but it must open to the outside, which makes the exterior door a less practical solution. Not any window will do.

As the name indicates, these fans are installed directly in the ceiling of the bathroom. The ceiling-mounted exhaust fan removes moisture and odors from the bathroom by expelling the suctioned air from the room, via the housing, through ductwork, and out the roof or overhanging soffit.

Bathroom vent fans must be vented to the out of doors. Venting this fan into the attic is simply asking for problems. The excessive moisture will cause condensation on the roof members, insulation and eventually cause mold. It is never OK to vent directly into an attic even if the attic itself is vented.

How long should a bath fan run after a shower is used? The Home Ventilating Institute recommends that a fan should be left on for 20 minutes more to clear humidity adequately and to ensure moisture and condensation in the fan body or ducting is minimized.

Exhaust fans with a UL listing for installation over a tub or shower on a GFCI circuit can be installed over a tub or in a shower. This applies to most Air King exhaust fans and exhaust fans with light. Units that include any type of heating function to them are not able to be installed over a tub or shower.

If your attic doesn’t have proper ventilation, the best way to increase the flow of fresh air through your attic is by adding vents to the soffit boards on the bottom of your eaves. Soffit eave vents work in conjunction with gable, roof, or ridge vents to provide a natural flow of air through your attic.

Ideally, half the vents should be located in the soffit at the bottom of the roof and half in gable or ridge vents near the top to allow for natural circulation of air through the attic. Example: a 50′ x 30′ attic would have a total area of 1,500 sq. ft., divided by 150 equals 10 sq. ft. of total vent space needed.

Also, soffit helps your building breathe. With vented soffit, air can flow through the vents to provide regular air circulation to your attic. Air flow is tremendously important for your entire home. Bottom line — you need to let your attic cycle the heat and moisture away from your house.

The soffit board is tucked away under the fascia board. It is usually the board that you see most of from street level. The soffit can be ventilated to allow the flow of air into the roof area. Without adequate ventilation, condensation will form in the roof void increasing the risk of timber decay.

The Types and Styles of Roof Vents

Box Vents:

Wind Turbines: Also called whirlybirds.

Power Vents: Power ventilators (roof or gable mounted) also known as PAVs (Power Attic Vents) have motors that turn large fans to drive hot air and moisture out of the attic.

Ridge Vents:

Off Ridge Vents:

Cupola Vents:

Soffit Vents:

The primary purpose for having an exhaust fan is to remove the moisture out of the bathroom. These fans help to control and eliminate bathroom odors. Additionally, they add to the safety of the home and it’s residents by reducing fumes from cleaning agents that could potentially cause health related issues.

Air movement is typically measured in cubic feet per minute (CFM). Ventilation rates based upon eight air changes per hour are generally suggested. For most bathrooms this works out to one CFM per square foot of bathroom area. For example, a 7′ x 10′ bathroom would require a 70 CFM fan.

Exhaust fans work by sucking hot or humid air out of a small, localised area, allowing fresh air to enter from elsewhere (perhaps a doorway or vent) in order to replace it. The warm air that’s drawn out using an exhaust fan is then pulled through a ducting system and expelled outside.

For bathrooms up to 100 square feet in area, HVI recommends that an exhaust fan provide 1 CFM per square foot (approximately eight air changes per hour) to properly ventilate the bathroom. Example: Bathroom is 8’x5′ (with 8′ ceilings). Multiply 8 x 5 = 40 sq. ft.

Sones are not decibels or volume, but rather how sound is sensed. Sones are a linear measurement, like inches. Doubling the sone value is equivalent to doubling the loudness (i.e. one to two, two to four is doubling the sound level twice). One sone is equivalent to the sound of a quiet refrigerator in a quiet kitchen.