How to Remove Air Pollution in the Home

We all want homes that are comfortable and energy efficient. But all our efforts to replace drafty windows, seal up air leaks, and blanket wall cavities with insulation have had an unfortunate consequence: They’ve made the air in our houses less healthy to breathe.

More of the airborne pollutants that once might have found their way outside—household chemicals, smoke, pet dander, and cooking gases, to name a few—are building up inside. Our well-intentioned efforts to restrict the flow of air in and out of our houses have led to indoor air-pollution levels that can be two to five times higher than those outside, according to the Environmental Protection Agency.

Indoor Air Quality

That doesn’t mean we should give up on making our houses tighter, of course. But it does mean now is a good time to pay as much attention to indoor air quality, or IAQ, as we do to energy efficiency.

That begins by getting a better understanding of how to balance the movement of air in and out of a house, and of mechanical systems that usher in fresh air and expel stale air without compromising energy efficiency—or comfort—in all seasons. Monitoring your IAQ is a useful first step in raising awareness, too. Because when we know what we’re up against, and how to minimize our exposure, we can all breathe easier.

Home Ventilators

Ventilation is the key to good indoor air quality. In the past, houses mostly relied on natural ventilation—air moving freely through windows, doors, and leaky walls—to flush out stagnant, contaminated air.

But sealing a house to prevent energy loss halts the healthy level of air exchange you get with natural ventilation. In 2012, as building codes demanded tighter construction for energy efficiency, requirements were added for whole-house mechanical ventilation. As TOH expert Richard Trethewey puts it: “If you’re going to insulate, you’ve got to ventilate.”

In most existing houses, mechanical ventilation is limited to bath fans and range hoods that exhaust steam or cooking odors. These fans remove the bad air, but often the fresh air needed to replace it—called makeup air—simply slips in through cracks in walls, down chimneys, and through basements and attached garages.

Not only is this air as hot or cold as the air outside, it’s very likely picking up contaminants on its way in. Extreme lack of makeup air can cause dangerous back-drafting of combustion appliances such as furnaces and gas-fired water heaters.

Energy Recovery Ventilator

A home’s ventilation system should balance the amount of air going out and coming in. And to save energy, you want to make sure the energy used (and paid for) to heat or cool your home doesn’t flow out with the stale air.

Enter the energy recovery ventilator, or ERV. This box-like device moves air in and out of the house while conditioning it to about the same temperature and humidity level as the air inside. You get fresh air, customized for a healthy, energy-efficient home.

An energy recovery ventilator ensures a steady supply of clean, conditioned air.

How does an ERV work?

Two fans draw air into the ERV: One brings fresh air in from outside the house, the other draws stale air from inside. The two airstreams are channeled past each other—but do not mix—in an exchange core made of a conductive material such as aluminum or plastic that allows the heat and moisture from one stream to transfer to the other. The ERV may be programmed to run periodically on its own, or may be activated along with a furnace blower.

ERV installation

The way fresh air is moved through a house via an ERV depends on factors such as the presence of existing ductwork, the age and efficiency of the furnace, and the layout of the home. Usually an ERV is tied into existing ductwork in a forced-air system (as shown, below). But an ERV can also be installed independent of the HVAC system, along with its own 6-inch ducts. This approach is typical in homes with electric or hydronic heat.

ERV system cost

ERV units cost between $800 and $1,500, with installation running $1,000 to $2,000, depending on the scope of the work. Some states offer rebates; to see if yours does, check the database of the NC Clean Energy Technology Center.

Balanced Ventilation System

This home’s balanced ventilation system relies on an ERV tied to an existing forced-air HVAC system. Along with kitchen and bath fans, it maintains indoor air quality without compromising energy efficiency.

1. ERV intake

Fresh air is drawn in through a duct and passes through the ERV’s core, where heat and moisture are exchanged. In this case, cold winter air is warmed by the outgoing conditioned air so the furnace does not have to work so hard to bring it to room temperature.

2. Furnace

In this home, air that is conditioned by the ERV passes through the furnace, where it is fully heated and then distributed through the HVAC ductwork.

3. Air return

Stale, conditioned air from bedrooms and living areas is drawn back toward the ERV, where most of it is exhausted outside after transferring its heat to the incoming air.

4. Bath vent fan

Odorous, moist air that can lead to mold and mildew vents directly outside to prevent recirculation through the house’s HVAC system.

5. Range hood

Cooking gases drawn through the range hood are ducted outdoors. This high-powered hood requires dedicated makeup air, which enters through a vent behind the cabinet that is activated when the vent fan is turned on.

6. Sealed fireplace

A sealed insert helps control both indoor air pollution and energy loss by sending combustion gases up the chimney, not into the room.

Other ways on how to improve indoor air quality

While a balanced system of mechanical ventilation is the most effective way to improve indoor air quality, here are some more steps you can take.

Boost your existing exhaust system

Make sure bath fans vent outdoors (and not into a ceiling or attic). Run them for 20 minutes each time the room is used, or install a switch that activates the fan when the lights come on. Replace a recirculating range hood fan with one that vents outside, and, if you can, add a makeup air damper nearby that opens when the hood is operating.

Upgrade air-handler filters

Filtration is no substitute for ventilation; still, regular replacement of your air-handler filter or, better yet, upgrading to a more effective electrostatic filter can cut down on the recirculation of irritants. Look for a filter with a MERV (minimum efficiency reporting value) rating between 11 and 14. Check filters monthly and replace if dirty, or at least every six months.

Spot-clean the air

Stand-alone air purifiers can effectively remove airborne contaminants in a confined space, says the EPA. Some filter both gases and particulates; others address one or the other. The Association of Home Appliance Manufacturers’ Verifide program tests air cleaners’ performance; check ratings at AHAM Verifide.

Shut the door on pollutants

Seek out no-VOC paints, cleaning products, and furnishings; look for third-party green certification seals. If you must introduce chemicals into your home, buy only what you need, and dispose of leftovers promptly.

Indoor Air Quality Testing

New interest in IAQ has led to a wave of devices that will keep tabs on your home’s air quality. Many will alert you via smartphone to changes in IAQ, or communicate with your smart thermostat to activate the ventilation system. “Knowledge is power,” says TOH home technology expert Ross Trethewey.

Decide what pollutant you want to monitor.

Not all devices track all pollutants. If someone in your home is allergic to dust or pollen, for example, you’ll want to make sure the one you select tracks those specific particulates.

Pay attention to the sensor.

The sensor is the most critical part of the monitor. A table of sensors tested by the EPA is available at epa.gov/air-sensor-toolbox. Be prepared to pay more for a good one.

Consider the next step.

Knowing that your indoor air is unhealthy only gets you so far. A monitor that can trigger ventilation either directly or through a smart thermostat ensures a quick response to poor IAQ.

Choosing an Indoor Air Quality Monitor

FOOBOT

Airboxlab

The Foobot tracks tiny respirable particulate matter (PM2.5), total VOCs (TVOCs), temperature, and humidity. Its LED display indicates overall air quality by glowing blue (good) or orange (bad); the app rates your IAQ on a numerical scale from 0 to 100.
$199; Foobot

AWAIR GLOW C

Awair

The retro-styled Awair 2nd edition (left) tracks temperature, humidity, CO2, TVOCs, and PM2.5. The plug-in Glow C measures only TVOCs, temperature, and humidity, but will trigger “non-smart” devices like air purifiers or fans that are plugged into it.
$199 and $89; Awair

LASER EGG


Kaiterra

With a clock-like appearance, both the Laser Egg (left) and Laser Egg+Chemical track PM2.5, temperature, and humidity; the latter also monitors TVOCs. Both are Wi-Fi-enabled and work with other home appliances via Apple Homekit and IFTTT.
$149 and $199; Amazon

TEMTOP M10

Temtop

The Temtop M10 has no Wi-Fi connectivity and no app, but offers at-a-glance readings of PM2.5, TVOCs, and formaldehyde with a series of clicks. Two other versions are available: The P10 measures only particulates; the M10i offers Wi-Fi connectivity.
$80; Temtop

AIRVISUAL PRO


IQAir

The AirVisual Pro rates household air using EPA’s Air Quality Index of 0 (good) to 500 (hazardous) and compares that score with locally reported conditions. It tracks PM2.5, temperature, humidity, and CO2, and recommends remedial action when IAQ is poor.
$269; IQAir

WAVE PLUS AND MINI

Airthings

The Wave Plus (shown) monitors temperature, humidity, air pressure, TVOCs, CO2, and radon, but not particulates. The desktop Wave Mini tracks temperature, humidity, air pressure, and TVOCs. Both offer app control and a color-coded display.
$269 and $79; AirThings

Factors That Increase Indoor Air Pollution