Ventilation Systems: The Good, Bad and Unhealthful

Ventilation Systems: The Good, Bad and Unhealthful

Many of us are relying on bathroom and stovetop vent fans for the peace of mind that comes with knowing they are removing stale or bad air. But most people don’t think about pulling fresh air in.

When a home is properly insulated and air leaks are sealed, fresh air can be lacking. In fact, for more than a decade, the U.S. EPA has warned that the tighter construction standards needed for energy-efficiency is causing a rise in indoor-air pollution — and major health threats. The solution is to bring in fresh air, in addition to removing stale, bad air.

Those who have been able to build Leadership in Energy & Environmental Design (LEED)-certified and other High-Performance Homes are most likely to have systems, such as an Energy Recovery Ventilator (ERV), that continuously pull in and filter outdoor air through the home’s HVAC system. But because an ERV can run $3,000 to $4,000 installed, some in the industry have looked to less-costly options.

Exhaust-only ventilation: Be careful what you’re breathing

“Exhaust-only” ventilation strategies are by far the most popular, because they are the least expensive.

And in theory, exhaust-only ventilation works. An exhaust-only strategy — most commonly bathroom or stovetop vent fans — pulls stale air out of the house, which is replaced by air coming into the house.  For every cubic foot of air you pull out per minute, the same amount is being brought back in, “allegedly fresh,” says Julie Tolliver, president of Energy Fitness for Homes in Cincinnati, Ohio.

t’s a terrible system,” Tolliver says. “Yes, it ‘works,’ by pulling stale air out and bringing outside air in. But you are bringing the air in through the worst possible places. Attics, crawlspaces, basements and gaps and cracks through the walls.  It drags in outside air, including pollen, dirt, spores and humidity, through gross places we never see, like through mouse poop, dead mice and nasty insulation, to circulate through our homes. And we consider it fresh air?”

Fortunately, there are other solutions that are less expensive than an ERV that filter the air they bring into the home.

What is an ERV?

An Energy Recovery Ventilator is an HVAC component that works by itself or in conjunction with a forced-air central cooling and heating  system. It gives the entire house fresh, filtered outdoor air, and it exhausts stale or contaminated air.

An ERV also reduces utility bills because it uses airborne heat energy to warm incoming air in the winter, reversing this process during the summer, when it extracts the heat from incoming air, sending it back out through the exhaust fan.

But because of cost and other climate considerations, the ERV system isn’t everyone’s first choice.

Supply-only ventilation with air filtration and dehumidification.

In Greater Cincinnati’s climate, with hot, humid summers and pollen-ridden air that often hovers in the Ohio River Valley, Tolliver favors supply-only ventilation systems, coupled with whole-home dehumidification that filters and dehumidifies incoming air as well as air inside the house.

The Santa Fe Ventilating Ultra Dehumidifier is one of Tolliver’s favorite options. It can be installed in your home’s ductwork, attic, basement or a closet, for focused or whole-house ventilation and humidity control. It uses MERV13 filtration to clean incoming air and has high energy-efficiency ratings.

Keeping tabs on home humidity levels, is very important. Air can become too dry when indoor humidity levels are less than 40 percent. On the flip side, humidity levels greater than 55 percent can cause mold growth. But continuous humidity monitoring is simple when you have a hygrometer, which can get for as little as $10 on Amazon or at your local big box store. Whole-home dehumidification prevents high humidity, which also feels more comfortable.

Still, supply-only ventilation dehumidifiers like the Santa Fe can cost up to $3,000 or more installed, depending upon which model you buy and your contractor’s charges.

Never fear. There are more options.

Fans with filters can work well, too.

Though some would call them primitive, there are other solutions homeowners can implement inexpensively, with moderate to no help from a contractor.

The most basic is making a box — with a Minimum Efficiency Rating Value (MERV)-13 filters — and attaching it to a sturdy box fan, using the fan to bring air into the home in a supply-only way — not out of the home in an exhaust-only way.

Tolliver says that you also can work with a contractor to install a sheet-metal tube — equipped with a pest screen, fan, filter and a damper — through a wall. It can be set to open for 15 minutes — as specified in ASHRAE 62.2 — every hour to ensure fresh air with contaminants filtered out is entering your home at regular intervals. Yes, this can be too cold in the winter, too hot in the summer, and not great for energy-efficiency.

But, Tolliver points out that a qualified contractor can design and connect a similar setup to your HVAC system through the ductwork. Fresh air then becomes part of your whole-home system, being filtered and dispersed through the existing ducts.

Don’t rely on popular air purifiers

Though they have become all the rage since the introduction of COVID-19, Tolliver cautions against popular purifies as a sole solution. Many of the them rely on colored light to kill germs and have inadequate filters or no filter at all. Filters with high efficiency ratings are key in improving indoor-air quality. 

And even when they contain the best filters, air purifiers by themselves don’t bring fresh air into your home.

“The ‘right’ amount of fresh-air ventilation can be calculated based on how tight your house is,” Tolliver says. “A home-performance or building-science expert can help you choose a solution tailored to your house, your lifestyle and budget that will provide high-quality indoor-air for you and your family year-round.”

— To reach Tolliver and our Ohio healthy-home team, email or call (513) 200-9471.

No Comments

Post A Comment