Indoor Air Quality in Residential Buildings

The vast majority of people in the US who own their homes live in single-family detached houses (80.6 percent). Renters, however, are more likely to live in apartment buildings with five or more units (44.7 percent). The third primary type of housing in the US, mobile homes, have been the fastest growing category of housing, increasing 152 percent from 1950 to 2000. The 1970s and 1980s were peak growth years for mobile homes, increasing by 2.5 million units in each decade, although growth has slowed since the 1990s (see Table 1). [1]

People in the US spend an average of 65 percent of their time at home and as much as 90 percent of their time indoors, according to a May 1999 national survey conducted by the American Lung Association. Additionally, 90 percent of homeowners questioned in this survey were not aware that poor indoor air could be a problem, yet another national survey conducted in 2000 found that about 95 percent of people who responded to that survey said they thought the quality of air in their homes was either somewhat or very important.[2]

The increase in awareness is due in part to educational efforts by the US Environmental Protection Agency (EPA) and other public interest groups. The US Department of Heath and Human Services and the Surgeon General's Office, for example, established a Healthy People Initiative. Their conference report estimated that 25 percent of preventable illness worldwide can be attributable to poor environmental quality, and that air pollution alone is associated with 50,000 premature deaths and more than $40 billion dollars in health-related costs. Indoor air pollution is one of the environmental causes of these illnesses.

Four primary reasons are at the root of poor indoor air quality (IAQ) in residences:

• Energy conservation measures, including tighter, well-insulated buildings
  

• Increasing use of synthetic building materials, furnishings and finishes
  

• Poor design and construction
  

• Occupant activities, including poor maintenance of the home and its heating, ventilating and air-conditioning (HVAC) system

In general, gaseous and particle pollutant levels in the home are often 2 to 100 times higher than those found outdoors. A home's furnishings, building materials, appliances, cleaning chemicals, and hobby materials are just some of the sources of these pollutants. Excessive moisture in homes from water leaks and uncontrolled humidity also can lead to elevated allergens and molds. A consequence of air tight and well-insulated building construction is less fresh air enters structure, which allows pollutant levels to increase by trapping air inside. Eventually, they can become irritating and unhealthy to home occupants. Some also contribute to unacceptable and noxious odors.

In some cases, homes that are built to conserve energy or that are built to be "tight" are more likely to have indoor air quality problems than homes that are kept "leaky", because air pollution from indoor activities and materials does not get adequately flushed out of the home. Also, in a home that is left intentionally leaky, there is no way to control the air that enters through cracks and other openings.

Improving indoor air quality in apartments is the same as in homes. The key is to reduce pollutants at their source and then increase ventilation; however, apartment residents do not have as much latitude in making changes to ventilation as someone living in a single-family detached home. Nevertheless, there are still things that can be done, such as unblocking an air supply vent or opening a window to temporarily increase the ventilation. Poorly controlled central heating in multi-family units may drive residents to use their stoves for space heating, which is extremely dangerous!

This was found to be the case in three public housing authorities where monthly gas usage was five times higher in winter where oil-fired boilers provided the central space and water heating.[3] In cases like this when only the building owner or manager is in a position to correct the problem, encourage them to follow the EPA and National Institute of Occupational Safety and Health (NIOSH) guidelines found in Building Air Quality: A Guide for Building Owners and Facility Managers.

New, energy efficient homes, and older homes that have had energy conservation features correctly installed can achieve good indoor environmental quality, because many pollutants are less likely to enter the homes, and those that do can be removed with controlled ventilation. These homes use exhaust fans to remove excessive moisture and cooking odors and a tight building shell makes sure that toxins in soil gas do not enter the home. These homes also are built and furnished with materials that are low emitting and thus are minimal contributors of indoor air pollutants. Click here to learn more about green homes.

Homeowners should be aware of the potential impact of poor IAQ on their family's health and take steps to minimize their exposures. This portion of the Aerias site takes a closer look at variables that affect IAQ in residential buildings, including: