Installing a Bathroom Vent Fan to Prevent Mold

Bathrooms generate more moisture than any room in your home, and when that moisture gets into attics, walls and ceilings, it will create mold sooner or later, and rot too.
Installing a bathroom vent during home construction is much easier than retrofitting a bathroom with one.
Whether or not it’s a DIY home project depends on your level of skill and experience. A couple of power tools are needed too.
Hiring an electrical contractor to do the work is very common, and we’ll include prices for this type of work below. Keep in mind that in your community, you might need a permit for the work. Discuss permits with the contractor you hire, or call your local building department.

Bathroom Vent Fan Installation Tips

This house repairs guide gives you tips for bathroom fan installation, so whether you do it yourself or hire someone, you’ll understand what’s being done and why.
We include a list of tools and materials required for the job. In addition, you’ll find bathroom fan installation prices for doing it yourself and for hiring a professional.
Tips for saving money on a DIY or professional job are included.
Finally, we provide resources at the bottom of the post. These are external sources that give instructions, pictures and more.

The basics of a bathroom exhaust system include a fan  on the bathroom ceiling and a vent on an exterior wall of the home or through the roof.
Connecting the two with a length of hose allows the moist air to be effectively vented, so it can’t penetrate the structure and create mold or rot. Here are vent fan installation tips, with more resources below.

• Remember to check on whether or not a permit is required – your local authority or contractor will know this
• The fan in the ceiling should pull air out of the bathroom and push it through the hose and out of the home
• Fans are rated by their CFM rating – the cubic feet of air per minute that they move
• Select a fan that moves at least 1.1 times the number of square feet of the bathroom, so, e.g., a 100 square foot bathroom needs a 110 CFM fan
• The fan should be located between the toilet and the shower for maximum effectiveness
• The fan mounting bracket attaches to two joists, and you might need a stud finder to locate the joist
• The wiring can go to an existing electrical feed to the bathroom, often where the light switch is, though a new switch will need to be added
• If your home has an attic, wiring the fan to an existing switch is fairly easy
• If there’s no attic, the job is much more difficult unless you run the wire outside the wall and conceal it with a cover
• The hole for the vent must be cut through the sheathing on the house and siding too, if it’s been installed
• The vent should mount to two studs in similar fashion to mounting the fan
• Once the vent is installed, the cover should be attached from the outside
• The vent hose should be securely attached to both the fan assembly and the vent using included hardware and clamps
• Shorten the hose, if necessary, to ensure that there isn’t enough excess for the hose to kink

Bathroom Vent Fan Installation Cost

These vent fan installation prices will give you an idea of what your costs will be for DIY projects and for hiring a professional contractor for the work.

DIY Bathroom Fan Installation Cost: The fan itself will cost $40 to $100 based on its CFM capacity and the quality. Some come as kits with a vent included. If not, the vent will cost $8 to $15 and hose typically costs $1 to $2 per foot. Here’s a list of the tools you’ll need and their costs. They are all offered in a range of quality, so that accounts for the price spectrums:

• Stud finder: $10 to $25
• Corded or cordless drill and bit kit: $40 to $100
• Jig saw: $35 to $100 or circular saw: $40 to $200
• Wire snips for cutting the hose: $12 to $30
• Roll of Romex wire: $14 to $100 depending on length needed
• Small package of wire nuts: $5
• Step Ladder for inside: $35 to $100
• Caulk and caulk gun to seal the outside vent: $20 to $50
• Extension ladder for outside: $75 to $200
• If you go through the roof, then you’ll need roofing cement, shingles and roofing nails: $30 to $60

Professional Bathroom Fan Installation Cost: This is a half-day job for a contractor. With the fan and other materials, the cost will be $150 to $300. The variable in costs include the complexity of the job, whether or not a permit is needed and the cost of living in your area.

Saving Money on Bathroom Vent Fan Installation

If doing the work yourself, the easiest way to save money is to borrow the tools required. Also, measure the amount of wire you need, and don’t buy more than is needed. Power tools can be rented, but the rental cost is typically pretty high, and you’d be money ahead in the long run to buy the tools, since they’re useful for many different house repair jobs.

When hiring a contractor, it always makes sense to get multiple estimates for the best price for where you live.

Additional Resources for DIY Bathroom Vent Fan Installation

Here’s more help for the job. The resources will give you a better idea of what you’ll need to do if you plan a DIY bathroom fan installation.

Hawk Environmental – This is an excellent overview of the job including how to know when to replace a bathroom fan and how to properly vent the fan hose.

Martys Musings – This post from a DIY blog has instructions with pictures that will help you understand exactly what you’re getting into.

AirKing – Here are some FAQs from a manufacturer of vent fans that will answer many of your questions.

Colonial Electrical – This information from an electrical contractor addresses the need for a bathroom fan.

Energy Vanguard – These pictures with descriptions show you how NOT to install a bathroom exhaust fan.