Stay Cool: Benefits of Ventilation Fans

By Susan Casey | Sep 15, 2014
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“Today we are building better houses than we ever built before, and part of that component is that we air-seal the houses. It’s the best thing you can do for an occupant, energy-wise, because the cost of heating is reduced considerably, and a house is easier to cool. But there’s a caveat: what comes into the home, stays in it,” said Ken Nelson, northwest regional sales manager, Panasonic. “As people come in and out the front or back door, airborne particles come in, containing allergens, chemicals and mold. Dust comes in with pets.”

What’s the solution?

“A house has to have an air change occurring within it. In the past, we relied on random winds or random air pressure changes to do that for us. Adding continuous ventilation is a key strategy to reduce or eliminate those things,” Nelson said. “Installing and operating a quality exhaust fan provides a path for water vapor or contaminated air to exit a house. All we have to do is take the crummy old fan most people have in their homes—usually in their bathrooms—and replace it with a quality fan with intelligent controls to create a low-cost, inexpensive, air-change solution.”

For new construction, procedures for exchanging air are required by codes, including the International Residential Code (R403.5), ASHRAE 62.2 and California’s Title 24.

“In California, a bit of a sea change in design was caused when the 2008 Title 24 California energy code related to continuous ventilation went into effect,” said Brian Berg, P.E., CEM, associate principal, mechanical engineer, Glumac, Irvine, Calif. “Title 24 is on the leading edge of code making and energy usage in terms of ventilation. It’s stricter than ASHRAE 62.2, which is the industry standard for ventilation. Some of the national codes are coming up to speed with practices we’ve been doing for a few years.”

Codes have pushed improvement of fan products as well. Fan controls are now more intuitive, which allows for features—such as continuous low-speed, motion and humidity sensing—that address both the indoor air quality (IAQ) and moisture issues.

“Fans can kick into action by detecting a quick rise in humidity,” said Patrick Nielsen, marketing manager, Broan-Nutone LLC, Hartford, Wis. “Let’s say a bathroom has a 40 percent relative humidity. The sensor may be set at 80 percent relative humidity. However, if the humidity level goes from 40 to 50 very quickly, the sensor reacts before the level reaches 80. This is a benefit to the homeowner, especially ones with teenagers who are known to take showers and forget to turn on the fan, a practice that can result in mold growth.”

Codes have also pushed improvement of motor technology in terms of energy output. A motor’s energy efficiency is measured in cubic feet per minute (CFM) of air it can move per watt of energy used.

“Permanent split capacitor [PSC] motors were an improvement on the previous generation of motor and allow for an Energy Star-qualified product,” Nielsen said. “Now, brushless direct current motors, or BLDC motors, allow you to get huge efficiency over the PSC motors. You can get extreme efficiency, running at only 5–8 watts and moving 80 CFM of air on 5–8 watts.”

How does this affect electrical contractors (ECs)?

“In the past, no one has been the front line on residential exhaust fans,” Nelson said. “We’re asking [ECs] to be the front line. With today’s homes, we have to consider indoor air quality and moisture management, and we have to make sure that our homeowners understand why those components are important. Electrical contractors can do that.”

[SB]What about heating, ventilating and air conditioning (HVAC) contractors? Doesn’t this fall under their domain?

“I think there’s a perception on the part of builders that HVAC tradesmen might be more well-versed and know a little more about air movement, and they want to make sure the fans are moving the right quantity of air,” Nielsen said. “HVAC contractors have been getting more of that business than electricians. Some new construction might favor HVAC contractors, but when it comes to retrofit or new construction where new codes and standards for ventilation are involved, the projects are more heavily weighted to electricians.”

Why haven’t ECs jumped on this business opportunity? In part, tradition. Typically on large projects, a general contractor hires mechanical and electrical subcontractors. In that scenario, the mechanical or HVAC contractor purchases and installs the fan and duct work as designed by the mechanical and electrical engineers. The EC brings power to the fan. The contractors work in tandem. On smaller projects, such as single residences, the EC can complete the job.

In light of the development of more efficient products that are easy to install, ECs could offer fan upgrades to their existing customers as well.

“For years, electricians shied away from offering fan upgrades,” Nielsen said. “I think it was due to the reality that it was hard to estimate an accurate quote without seeing the situation firsthand. Traditionally, to change a bath fan meant crawling up in an attic, getting full of insulation and covered in cobwebs. New products have installation systems that allow for installation to be done from the room side. Today, an electrical contractor can approach a homeowner and quote with confidence.”

Be in the know

ECs must know a few things to get into fan installations. For instance, contractors need to keep noise level in mind.

“If we have to put in a constant, continuous fan, it may be something the resident is not used to,” Berg said. “We work with acoustical engineers to design systems so the resident is not going to hear it or be annoyed. Some of the current fans on the market are very quiet. Residents seem to be OK with those. We don’t get too many complaints as opposed to squirrel cage fans that feature a grill with the fan on its other side and duct work leading to outdoors. That is the noisiest option.”

Yet solving noise problems is not that simple.

“Noise level is cumulative. The longer a fan runs, the quieter it has to be to meet the standard,” said Samantha Rawlings, acoustical engineer, senior associate, LEED AP, Veneklasen Associates, Santa Monica, Calif. “One other thing to consider with the motors is the rpm. How quickly are they spinning? The noise is directly related to the speed of the fan. Motors themselves can generate a lot of vibration, so we often isolate them from the building structure. Otherwise, their physical movement can transmit vibration into the structure. Once it’s there, it radiates off walls, ceilings. You can hear it.”

Strategies for mitigating noise level range from product selection to placement. Some new fans are very quiet, i.e., 0.3 sones. And then there’s positioning. On a recent high-rise apartment house renovation project in downtown Los Angeles, Berg and his team’s design moved the fans away from the grill—inline fans—placed somewhere within the duct run. 

“Moving the fan a little farther away from the restrooms themselves dampens some of the noise so the residents can’t hear it,” he said.

Selecting the proper size fan for a home relies on a matrix. ASHRAE allows the ventilation calculation to be made in different ways. One way is to do the math based on square feet of living area and the number of bedrooms plus one. Another way is to use the chart, provided by ASHRAE, on page 36. Information about codes and guidelines are provided by the Home Ventilating Institute (, a nonprofit association of home ventilation products manufacturers founded in 1955.

To enter this market, ECs need to know that IAQ matters. That is a message that can be passed on to homeowners who may not be aware of the health, convenience aspects and economic advantages of indoor air quality and moisture-management products.

About The Author

CASEY, author of “Women Heroes of the American Revolution,” “Kids Inventing!” and “Women Invent!” can be reached at [email protected] and





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