Improving indoor air quality: From basic to better and best steps
According to the U.S. Environmental Protection Agency (EPA), indoor air is often more than 10 times (and sometimes, more than 100 times) more polluted than outdoor air. Indoor air pollutants contribute to asthma as well as other respiratory conditions and diseases.
Indoor pollutants include
- Volatile organic compounds (VOCs) from offgassing building materials, paints and finishes and furnishings.
- Other toxic chemicals emitted from cleaning products, pesticides and hazardous household supplies.
- Mold, which grows on moist materials and surfaces.
- Carbon monoxide and nitrogen dioxide gases, which can be released from gas-fueled combustion appliances.
- Particulates from wood-burning fireplaces or cars running near the house.
- Tobacco smoke.
Indoor air quality (IAQ) can be particularly compromised during winter and summer months, when the home is more likely to be sealed tight to keep heated or cooled air from escaping.
The three general strategies for improving IAQ are
- Source control.
- Improved ventilation.
- Air cleaning.
Source control—eliminating sources of pollution or reducing their emissions—is the most effective and should be the first step you take. Many source control options are easy and inexpensive.
Improved ventilation will improve indoor air quality by increasing the amount of outdoor air coming into your home, diluting concentrations of indoor pollutants, and pushing stale indoor air out of the home. However, some ventilation improvements may increase energy costs unless you make design changes to your home. The third strategy, using mechanical air cleaners to filter pollutants out of your indoor air, can be used to supplement source control and ventilation but it is not recommended as the sole solution.
Below is a range of tips—from basic to better to best practices—for protecting and improving the air quality in your home. For additional information about indoor air quality and healthy homes, visit the EPA’s Indoor Air Quality website or the American Lung Association’s Health House website.
Basic Steps to Cleaner Air
These easy and inexpensive source control measures will eliminate pollution or reduce emissions from cleaning products, gas appliances, building materials and furniture.
1) Clean with the least toxic product that will do the job.
The powerful chemicals in many conventional cleaning products can have a toxic effect on human skin and lungs. In addition, the propellants in aerosol products can be inhaled, so it’s prudent to use pump products instead. Find out how to make nontoxic cleaners from common household ingredients (such as vinegar and baking soda). Or, you can purchase nontoxic or less-toxic formulated cleaning products at most stores. GreenSeal, Greenguard, and Scientific Certification Systems (SCS) certify residential cleaning products that comply with their green standards.
2) Avoid having your clothing conventionally dry cleaned, or air out dry-cleaned clothing before bringing it inside.
Perchloroethylene (PERC), the most commonly used dry-cleaning solvent, is a potential carcinogen. In the report Hung Out To Dry, the Coalition for Clean Air recommends allowing cleaning solvents to offgas by removing clothes from the plastic dry-cleaning bag and placing them outside for four to five days. Alternatively, most fabrics that are labeled “dry clean only” can actually be cleaned through a PERC-free “wet cleaning” process that is increasingly being offered by professional dry-cleaning shops, or some can even be cleaned at home using a mild soap. For more information on alternatives to toxic dry cleaning, read Green America's article on the topic.
3) Dispose of unused paint, solvents, pesticides and other household chemicals promptly, and tightly close the containers of products still in use.
These products can emit harmful gases that pollute the air and may cause health problems. Minimize the use of hazardous products as much as possible. For essential household chemicals, buy them in smaller sizes that you can use right away. Earth 911 offers an easy-to-use national directory of safe disposal sites for toxic household wastes. If you need to store any hazardous chemicals, keep them in a ventilated and locked outdoor shed away from children, pets and flame sources.
4) In temperate climates, use natural ventilation to cool your home.
A natural ventilation strategy relies on the buoyancy of hot air (the stack effect) and wind (cross ventilation) to increase the amount of outdoor air coming into your home. Natural ventilation can reduce total energy consumed by 10 to 30 percent compared with a home using a forced-air cooling system.
Although natural ventilation is best incorporated into a home’s overall design (e.g., proper window placement when designing the home), there are simple ways to apply natural ventilation in any home: open both the top and bottom sashes of double-hung windows, and open windows on opposite sides of the same room for cross-ventilation. Opening windows at night during the summer will bring cool, fresh air inside, and the thermal mass of the house will help the interior stay cool for part of the next day. The greater difference in temperature between inside and outside air at night also will cause more rapid air exchanges and vent air pollution from inside more thoroughly. In addition, outside air may be cleaner at night due to fewer cars on the road.
5) Use the exhaust fan over your stove to remove gases like carbon monoxide and nitrogen dioxide and the fans in your bathrooms to remove water vapor.
Make sure your gas range has a hood fan that exhausts to the outside—some exhaust systems are ductless hoods that exhaust air pulled from the stove right back into the home. Bathroom fans are also important since poor moisture management in a home can allow molds to grow. Also, if your home’s walls, doors and windows are tightly sealed and energy efficient, you may need to open a window slightly when running an exhaust fan or when you’re using a fireplace, to avoid creating negative pressure. Without another way for outside air to replace the air leaving through the exhaust fan or chimney, air may be drawn through the exhaust pipes for your furnace or hot water heater.
6) Employ other simple moisture management measures to keep your home’s interior dry.
Be sure to fix any leaks and clean up any household spills as quickly as possible. Standing water and moist materials provide a habitat for mold and microbial growth (and can also attract pests).
7) Replace the air filter in your furnace and air conditioner at the start of the heating or cooling season, or as recommended by the manufacturer.
Filters actually become more effective in capturing and removing particulate air contaminants as they get dirtier and build up a “dust cake.” This increased effectiveness comes with a cost, however, as the pressure drop increases and less air gets through. It is a good idea to change the filter for the furnace at the start of the heating season, as the dust cake from the previous year has been sitting in the cold, dark basement throughout the summer and may have started to grow molds.
8) Room-size air cleaners can be effective tools for removing pollutants in one or more rooms.
If you are concerned about pollution in a particular room and it’s not possible to remove the pollution source, consider buying a room-size air cleaner. Some sources recommend air cleaners for improving air quality in one or several rooms, but not for the whole house. See the EPA’s Guide to Air Cleaners in the Home for information on the various types of air cleaners.
9) Don’t allow smoking inside your home or around your home (near your windows or doors).
This one may seem obvious, but lest anyone forget, tobacco smoke is a pollutant.
Better Steps to Cleaner Air
These steps to improved indoor air quality are modestly priced, but may require some advance planning.
1) Remodel during temperate months of the year, when you can open outside doors and windows to naturally ventilate construction areas without reducing energy efficiency.
During the winter and summer months, when heating or cooling systems are in use, opening doors and windows will reduce your home’s energy efficiency. So if you’re doing any remodeling or home improvements that involve noxious fumes (e.g., painting, gluing, sealing), it’s best to do the work when the weather is mild and you can have doors and windows open.
Direct floor fans toward the open windows to exhaust the fumes outdoors. Also, when applying emitting finishes, such as paint, remove absorptive items (such as upholstered furniture and rugs) from the room so that they don’t absorb and re-release the VOCs.
2) Use low-emitting, low-maintenance building materials to achieve improved indoor air quality year-round.
Selecting low-VOC (low in volatile organic compounds), low-emitting, low-maintenance products can help you reduce the amount of pollution released into your home’s indoor air, thereby avoiding the need to take more drastic steps to clean dirty air. Green Home Guide has advice on selecting healthy flooring, furniture, paints and coatings, and insulation (formaldehyde-free). Also, look for low-VOC adhesives and caulk and for pressed wood products (e.g., particleboard) that do not contain urea-formaldehyde. Greenguard, GreenSeal, and the Carpet and Rug Institute (Green Label Plus) certify building products that meet IAQ criteria.
3) Reduce the amount of carpeting, and keep it clean and dry.
Carpeting can absorb water and trap particulates and other contaminants; some types of carpeting also contain high levels of VOCs. Where possible, select a nonabsorptive type of flooring. Never use carpeting in the kitchen, bathroom, laundry room, basement or other areas of the house that are regularly exposed to moisture. Areas that are carpeted should be vacuumed regularly, ideally with a HEPA (High Efficiency Particulate Air filtering) vacuum. And if carpeting gets wet, make sure that it is completely dried within 12 hours to prevent mold growth. When having carpeting professionally cleaned, you can choose a company that uses a no-chemical and low-water process.
4) Add a fresh air intake to your forced-air heating/cooling system’s ducting.
A fresh air intake will allow fresh replacement air to enter the house when you’re using exhaust fans or the fireplace. If you already have a ducted air system, you can add a dedicated outdoor air opening by extending the return-air ductwork to the outside. To ensure fresh air delivery, use a system with automated circulation (e.g., a fan-cycler). You may also want to install a filter in this outdoor air source to capture air contaminants such as pollen and prevent them from entering your house.
5) Install a whole house fan system.
A “whole house” fan system brings stale indoor air upwards and out the top of the house through the attic vents. This type of fan system also provides a good, energy-efficient alternative to air conditioning on moderately warm days. (Note: If you live in a particularly humid climate, also consider using a dehumidifier.)
6) Design your garage to keep vehicle fumes from entering your home.
If you’re building a new home, consider building a detached garage (or no garage). If you have an attached garage, tightly seal the wall between the garage and your conditioned space, and install an exhaust fan system that either runs continuously or uses an automatic timer linked to an occupancy sensor, garage door opener, or carbon monoxide detector. Also, do not install HVAC equipment or air-handling ductwork in the garage.
Best Steps to Cleaner Air
Even if you take all of the steps above, your home could still contain sources of indoor air pollution. The following are some additional technologies and strategies that may be more complex or costly to implement, but they can provide substantial improvements in indoor air quality.
1) Install an energy recovery ventilator (ERV) to provide a continuous supply of fresh air while minimizing loss of heat and water vapor.
This ventilation system (also referred to as an air-to-air heat exchanger) is connected to the existing forced-air heating/cooling system and uses fans to exchange stale indoor air with fresh outdoor air. Note that these systems cost several thousand dollars, so they do not have an immediate payback. To make sure that the incoming air is adequately filtered, select a system that has a HEPA (High Efficiency Particulate Air) filter, or a filter with a high MERV (Minimum Efficiency Reporting Value), i.e., a minimum MERV of 8 or, even better, 10 or higher.
2) Use a heat pump water heater to increase energy efficiency and improve indoor air quality.
Heat pumps achieve energy efficiency by moving heat around, as opposed to liberating it—the heat for the next batch of water to be heated is reclaimed from the warm, humid air being exhausted. Heat energy comes both from cooling the air being exhausted from about 72° F to 42° F (sensible heat reclamation) and from the condensation of the water vapor back into a liquid (latent heat reclamation). Heat pump water heaters use 30 to 50 percent of the electricity consumed by conventional electric water heaters.
The improved IAQ stems from the moisture management aspect of this approach. The amount of mechanical ventilation provided directly matches the amount of hot water consumed. Also, because the hot water use reflects the level of human occupancy (with more people in the home, more washing occurs), the result is mechanical ventilation with heat recovery that corresponds to occupancy levels. However, some experts have expressed concerns about the reliability of heat pump water heater systems. For guidance on how to select the right system and have it properly installed, read this article from the Department of Energy.
3) Install a radiant hydronic heating system rather than a forced air system.
Forced air systems stir up dust and allergens because they heat a home by blowing heated air into it. Radiant hydronic systems heat a space by pushing warm water through tubes underneath the floor; the warm floors radiate heat, rather than pushing air and dust around. It is easiest to install a radiant heating system when building a new home or an addition, but they can also be added to existing rooms.
How to reduce the use of VOCs in your home
Thanks to David Bearg and Dean Sherwin for their edits and advice on this article.