Fan fight: builders and engineers debate proposed ventilation standards.

In the works for more than six years, 62.2, ASHRAE's first residential indoor air quality standard, recommends that every new home come with some form of continuous mechanical ventilation--such as a super-quiet, continually running bathroom fan vented to the outdoors; a heat- or energy-recovery ventilator; or a controlled air inlet into the return side of the air conditioning system's air handler. It also says each bathroom and kitchen should have an exhaust fan vented to the outside for spot ventilation.

In addition, the guidance, which is expected to be incorporated into some local building codes by around 2008, calls for ventilation in garages and unconditioned attics and crawlspaces that are adjacent to living areas and for builders to do a backdraft test on some water heaters located within a home's living area.

The standard, which is voluntary until code officials opt to incorporate it into local laws, is "good, basic common sense," notes Max Sherman, a Lawrence Berkeley National Laboratories engineer who chaired the ASHRAE committee that wrote it. "People need fresh air. The standard tells how to provide it."

Sherman says the envelope of the modern energy-efficient home is so airtight that fresh air can't penetrate it in the quantities needed for healthy indoor living. Occupants of homes with stale, dirty air, he notes, suffer from maladies ranging from asthma to allergies, and their homes are at risk for damage from mold.

And Sherman says the cost to comply with the standard is between $100 and $200, as most builders already install bathroom and kitchen fans and could meet the requirement for continual ventilation by upgrading just one of them to an ultra-quiet model that residents would be willing to run all the time.

"You certainly could spend thousands to meet the standard it you want to, but that's a question of design," the engineer says. "If you set out to meet the standard in a cost-effective manner, it doesn't cost that much. Some builders are already doing it and don't even know it."

Indeed, Patrick Nielsen, product manager for bath fans at Broan-NuTone, estimates 90 percent of builders already install bathroom fans that meet ASHRAE's minimum requirement for airflow of 50 cubic feet per minute (cfm), a measure of how much air the fan moves. But because noisy fans are less expensive than quiet ones, most builders choose fans with a sound--or sone--rating of 4 or higher, which is about as loud as a normal conversation or the comfortable volume on a television or radio.

ASHRAE says bathroom fans that provide intermittent ventilation should have a sone rating of no higher than 3, and those intended for non-stop operation--only one such double-duty fan is needed per house--should carry a sone rating of 1 or less, the equivalent to the unobtrusive sounds of a quiet night in the suburbs. Sherman says homeowners are more likely to let a fan run around the clock if it's so quiet they can't hear it.

Builders pay about $10 for a Broan-NuTone fan with a sone rating of 4; $25 to $30 for a fan with a sone rating of 3; and $70 to $80 for a fan with a sone rating of 1, Nielsen estimates.

"It's not going to break the bank at all," notes Juneau, Alaska, custom builder Marquam George, a member of the ASHRAE committee that wrote the standard.

But custom builder Dwight "Sonny" Richardson Jr., NAHB's representative from Alabama, disagrees. He says he will have to increase the size of the air conditioning units he installs by a half ton per floor if he is forced to vent bathrooms and kitchens to the outside.

"If we have to design for the extremely hot and the extremely wet, it's more front-end costs for the equipment and also higher operational costs," the builder says, explaining that a larger air conditioning system installed to accommodate summer humidity will sit dormant for much of the year.

Besides, Richardson notes, the Tuscaloosa lifestyle involves often-open windows and doors, so plenty of fresh air finds its way into even the tightest homes. "We're caught in a catch-22," he says. "If we get the reputation of building houses that are expensive to heat and cool, then we're shot."

Yet some--even manufacturers who stand to benefit from increased sales of ventilating equipment should the standard find its way into local building codes--say the document doesn't go far enough. The guidance says the mechanical ventilation system should draw outdoor air inside at a rate of 7.5 cfm per person plus 1 cfm per 100 square feet, an amount Dennis Dietz vice president of engineering for American Aides Ventilation, says is half of what people need for healthy living. "This is going in the wrong direction," he says, adding, "The standard does a disservice."

Nielsen agrees that "it's definitely a very minimal standard." But he adds, "We're definitely at least making ground. There are still too many basic 50-cfm bath fans going in very large bathrooms. I'd like to think that [the standard] is slowly making progress on that."

George, who admits that the standard "most certainly was a consensus" that "didn't get out what the committee wanted out there"--partly because of NAHB's opposition--adds, "It's a great step in the right direction ... for both the consumers and the builders out there."

Production builder Max Wade, vice president of Artistic Homes in Albuquerque, N.M., goes further: "It's absolutely necessary. Yes, those things add to the price of the home, but the potential liability and actual liability are far greater than how realistic it is just to put in the fans."

In Minneapolis and Washington, every builder already installs mechanical ventilation because building codes require it, as do local codes in various cities around the country. "It's working out fine," says Ed VonThoma, product development manager for Centex Minnesota, who says the builder has had fewer callbacks and "comfort complaints" since it started installing in-line fans in mid-range homes and heat recovery ventilators in upper-end models.

But what's necessary up North may not be a best building practice nationwide, says NAHB's Inks. "There's no dispute that whole-house ventilation is a viable means for controlling ventilation and indoor air quality, but in terms of establishing a one-size-fits-all approach, it's not the way to go," he says.

Inks objects to a standard that he says is based on a subjective definition of "acceptable indoor air quality"--ASHRAE calls it air that satisfies "a substantial majority of occupants"--and a lack of data to substantiate the need for mechanical ventilation. In addition, he says a good test for backdrafting is not available.

"This is not to say that this kind of guidance is not needed," he concedes. "But why don't we take a different tack and develop a guidance document that would allow us to be much more flexible?" In fact, Inks notes, NAHB is creating such a guidance for its members. "You're better off to provide guidance [rather than a standard that could become law] because home construction varies so greatly from area to area," he says.

Richardson agrees. "We always prefer a market-driven approach, and we always prefer an education approach to mandatory things," he says. "We think a consumer is fully capable of understanding and telling a builder what he wants."--This story first appeared in BUILDING PRODUCTS magazine.

The ASHRAE Guidance

Vent bathrooms, kitchens, toilets, and laundry rooms directly outdoors. Use energy-efficient and quiet fans.

Avoid locating furnaces, air conditioners, and ductwork in garages or other spaces where they can inadvertently draw contaminants into the house.

Properly vent fireplaces, wood stoves, and other hearth products; use tight doors and outdoor air intakes when possible.

Vent clothes dryers and central vacuum cleaners directly outdoors.

Store toxic or volatile compounds such as paints, solvents, cleaners, and pesticides out of the occupiable space.

Minimize or avoid unvented combustion sources such as candles, cigarettes, indoor barbecues, decorative combustion appliances, or vent-free heaters.

Provide operable windows or additional mechanical ventilation to every space to accommodate unusual sources or high-polluting events, such as the use of home cleaning products, hobby activities, etc.

Use sealed-combustion, power-vented, or condensing water heaters and furnaces. When natural-draft applications must be used, they should be tested for proper venting and should be located outside the occupiable space when possible.

Put a good particle filter or air cleaner in the air handling system to keep dirt out of the air and off of the ductwork and heating and cooling components. Maintain it or replace it regularly as required.

Distribute a minimum level of outdoor air throughout the home using whole-house mechanical ventilation.

Source: American Society of Heating, Refrigerating and Air-Conditioning Engineers' Standard 62.2-2003, Ventilation and Acceptable Indoor Air Quality in low-Rise Residential Buildings, and 2001 ASHRAE Handbook, Fundamentals, Chapter 26, Ventilation and Infiltration