Last week’s article focused on replacing an existing vent fan, I mentioned that replacing a vent fan was easier than installing a new one where one never existed, so this week we will look at why that is. The trade skills needed to install a new vent fan, where none previously existed include carpentry skills, electrical skills, ducting skills, roofing skills and possibly drywall skills if you mess up the ceiling during the process.

To start with, choose the location you would like for the fan to be. Then go up into the attic and make sure there are no obstructions that would prevent the vent fan from being installed in that spot. Things to look for would be the ceiling joists, even the roof rafters, if you were choosing a place along an outer wall. The size of the vent fan’s outer box varies but averages about 10 to 12 inches square and about 6 to 10 inches high, depending on the brand and features of the unit, so it’s good to check the attic space to make sure you don’t cut a hole in the ceiling from down below only to find out later that the “rough in” housing box won’t fit the space or that a ceiling joist is in your way.

Once you have the space selected, you will want to try and rotate the “rough in” box in such a way that you can access the electrical box and the direction the duct work will face. You have to be able to gain access to these two areas. If it’s not possible to access these after the housing is secured to the framing, then you might want to wire up the box and secure the ductwork to the outlet before actually mounting the housing to the joists.

Speaking of wiring, you have to find a source of electricity and send it through a wall switch and from the switch back up to the vent fan electrical connection box. This project requires a level of intermediate skill so I’m assuming a serious do-it-yourselfer possesses these skills, if not, enjoy the article’s content and hire someone to install your fan. So I will skip the details of how to wire the switch and what size wire is needed, etc. those details would be an article in itself.

The new code requirements dictate that the duct work needs to be vented to the outside through the roof, (this is where the roofing skills kick in. A roof vent is made just for this application. It’s not the typical “turtle shell” vent that you often see in the roofs of patio homes, also referred to as static vents. Static vents cost about $8 to $10 each. These specific roof vents for exhaust fans have a heavy gauge steel body that is smaller in size and curves slightly downward with a back-draft door or flap to prevent wind from blowing back down into the room as well as a heavy hardware cloth to keep out those that don’t need to be there such as birds and squirrels. It also has a 4-inch diameter connector on the attic side to conveniently secure your ductwork to. This type costs about $30.

Of course, you may have seen other vent fans, either in your attic or in the attic of others, that had no ductwork at all or if they did the duct just ended somewhere in the attic space and caused you to wonder why you would want to go through the added trouble and expense to install a roof vent cap?

Good question! There have been many installed over the years in that manner without any noticeable negative consequences but keep in mind, the moisture you’re removing from the interior of the bathroom is being transferred into the attic and ask yourself, “Am I OK with that?” Not to mention that the code enforcers are always lurking about to find someone violating the new vent code – just kidding. However, the codes are there to provide us minimum guidance on the best practices to protect our homes and lives so it is good advice to follow.

JD Norris is the owner/operator of DreamMaker Bath&Kitchen and a certified S.C. Master Builder, certified “Aging in Place” Specialist and certified Green Professional. If you have any projects that you would like discussed in an upcoming article, email me at