Installing a bathroom fan that works

Cold weather is on its way, and this means bathroom exhaust fans will become more important.

Cold weather is on its way, and this means bathroom exhaust fans will become more important.

Without the ability to open a window all the time to let out steamy shower air, winter is the season when the integrity of your home depends on effective mechanical ventilation.

So how’s yours doing? Does it create more noise than good? There’s still time to make things right before temperatures drop and windows steam up, and work begins with a simple calculation.

To be effective, a bathroom fan needs to change all the air in your bathroom at least eight or nine times an hour. Ten is even better.

Any less than this and excess moisture will have a chance to damage walls, ceilings and windows before it’s drawn outdoors. If the moisture ever gets out at all, that is.

Begin by determining the size of fan you need by multiplying the bathroom’s length, width and ceiling height in feet. Set this number aside for a minute then look at the fan you’ve got (or the one you’re planning to install).

All exhaust fans are rated in cubic feet of air moved per minute (CFM), so you’ll have to multiply this number by 60 to get an hourly figure. Can the fan you’re looking move at least eight times the total volume of air in your bathroom in 60 minutes?

If not, you need a bigger fan, but watch out. Standard bathroom exhaust fans only work properly in the tiniest of bathrooms. If you’ve got anything larger than an ordinary bathroom, you definitely need a larger than ordinary fan.

Noise output is another issue. Larger fans are usually slightly louder, though you should never go for a quieter fan that’s not big enough. Even today’s largest bathroom fans generate a background sound somewhere around one “sone”. This is a unit of sound output used in the exhaust fan industry, and a one sone rating is quiet indeed.

The last time I installed a bathroom fan in an existing bathroom, the unique shape of the fan unit I chose made the job much easier.

It was a Panasonic WhisperFit model designed especially for retrofit situations. The unit is thinner than comparable fans made for new construction, with a housing depth of 5 5/8 inches versus eight inches for standard designs.

One of the biggest challenges when installing an exhaust fan where none existed before is electrical supply.

It’s one thing to cut a hole in the ceiling and route new ducts to the outdoors, but it can be very disruptive indeed to cut into your walls to re-route wires and install a switch.

An easy way around this is to tap into an overhead light fixture to power your new exhaust fan.

It’s usually a matter of running a few feet of new cable to the fan itself, directly from the box powering the light fixture nearby.

This approach eliminates the need to install a new wall switch. Your exhaust fan simply comes on and off with the light.

While the fan you choose is certainly important, the way it performs also depends on the kind of duct you select and the care with which it’s installed. If your duct is travelling through a heated area on its way outdoors, you’ll get best results using four-inch diameter metal pipe and elbows.

To maximize the output of the fan, and to keep moisture from escaping into attics and ceiling cavities, make sure all seams are covered with a layer of aluminum sealing tape.

This works much better than duct tape because it never lifts or peels off in time.

For installations where duct will travel through an unheated attic space, you’ll need to use flexible, insulated ducting to prevent warm, moist air from condensing on its way out of your house. Never let an exhaust fan vent into the attic space.

Exhaust fans are one of those home features that are usually less than they should be.

Invest the time and effort to address the important details and you’ll enjoy an effective installation that works like it should.

Steve Maxwell is Canada’s award-winning home improvement expert, and technical editor of Canadian Home Workshop magazine. Sign up for his free homeowner newsletter at www.stevemaxwell.ca

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

A GoFundMe campaign to support a Stettler couple following a fire has raised more than $3,000. (Contributed photo)
Family pet dies in Stettler fire

GoFundMe page has raised more than $3K so far

Canada's Alexis Lafreniere celebrates after defeating Russia 4-3 in the gold medal game at the World Junior Hockey Championships, Sunday, January 5, 2020 in Ostrava, Czech Republic. THE CANADIAN PRESS/Ryan Remiorz
As Alberta’s COVID-19 cases rise, so does tension over world junior championship

Alberta’s spike in COVID-19 infections and the virus’s infiltration of Canada’s team… Continue reading

Alberta’s chief medical officer of health, Dr. Deena Hinshaw, said growing COVID-19 case numbers continue to be a concern in the province. (Chris Schwarz/Government of Alberta)
Alberta announces 1,077 new COVID-19 cases Thursday

There are currently 14,052 active cases in the province

Carolina De La Torre, right, owner of Arepas Ranch in Calgary, poses for a photo with her husband in this undated handout photo. The Venezuelan woman who believes she was used as part of Jason Kenney's argument not to lockdown restaurants in the province remembers her encounter with the premier as a lot less dramatic than he suggested. THE CANADIAN PRESS/HO, Carolina De La Torre *MANDATORY CREDIT*
‘No crying’: Venezuelan refugee Kenney cited says interaction was less dramatic

EDMONTON — The Venezuelan woman who believes she was used as part… Continue reading

In this photo released by the official website of the office of the Iranian Presidency, President Hassan Rouhani waves to the crowd in a public gathering at the city of Yazd, some 410 miles (680 kilometers) southeast of the capital Tehran, Iran, Sunday, Nov. 10, 2019. Iran has discovered a new oil field in the country’s south with over 50 billion barrels of crude oil, Rouhani said Sunday, a find that could boost the country’s proven reserves by a third as it struggles to sell energy abroad over U.S. sanctions. (Office of the Iranian Presidency via AP)
Iran nuclear scientist assassinated

THE ASSOCIATED PRESS DUBAI, United Arab Emirates — An Iranian scientist that… Continue reading

skip2
Rimbey Christian School students experience the joy of giving

Grades three and four students raised $2,000 for Somalian children

kkk
Opinion: We’re weary of the wait for COVID vaccine

It’s official: vaccines are the new toilet paper. Justin Trudeau appears to… Continue reading

Actor Johnny Flynn portrays David Bowie in the film "Stardust" in this undated handout photo. THE CANADIAN PRESS/HO, Elevation Pictures *MANDATORY CREDIT*
‘Stardust’ is a Bowie pic without his music but that was always the plan: director

TORONTO — Gabriel Range’s controversial David Bowie drama “Stardust” has angered fans… Continue reading

Canadian figure skating champions Tessa Virtue and Scott Moir come to Penticton Oct. 6 with the Rock the Rink tour. This will be the pair’s last tour as they have announced they are retiring from the world of competitive figure skating. (Contributed)
Ice-dancers Moir and Virtue among 114 Order of Canada inductees

OTTAWA — Champion ice-dancers Scott Moir and Tessa Virtue are among 114… Continue reading

Mahomes vs. Brady spices up Thanksgiving holiday week

Mahomes vs. Brady spices up Thanksgiving holiday week

Cowboys miss chance for NFC East lead with another home loss

Cowboys miss chance for NFC East lead with another home loss

Arsenal, Leicester, Hoffenheim advance in Europa League

Arsenal, Leicester, Hoffenheim advance in Europa League

Keegan Messing performs during the Men's Short program at the 2020 Canadian Tire National Skating Championships in Mississauga, Ont., Friday, Jan. 17, 2020. If the world figure skating championships do go ahead in a bubble in March in Sweden, there is a good chance Canada won't be there. THE CANADIAN PRESS/Frank Gunn
Canada might not compete at world figure skating championships – if they happen

Canada might not compete at world figure skating championships - if they happen

Most Read