The evidence that improving indoor environmental quality (IEQ) can increase comfort, decrease adverse health effects, decrease absence rates, and increase work and school work performance is presented in other sections of this web site. This section provides estimates at the national level of some of the benefits and costs of taking practical steps to improve indoor environmental conditions in U.S. buildings. The estimates account for the existing IEQ conditions in buildings that are subject to practical improvement, the expected size of improvements in health, absence, and performance when IEQ is improved, and (when possible) the costs of improving IEQ. The estimates rely on journal-published analyses that take advantage of recent large advances in information about the impacts of IEQ on people's health and performance.
Increased Ventilation Rates: When the rate of outdoor air supply (ventilation rate) is increased, the indoor air concentrations of many pollutants emitted from sources inside the building are diminished. As reviewed in the section of this web site on building ventilation, throughout the normal range of ventilation rates encountered in buildings, higher ventilation rates are on average associated with fewer adverse acute health effects and improved office work performance. There is also evidence that occupants of buildings with higher ventilation rates have lower rates of absence from work or school, and improved schoolwork performance. The primary standard for minimum ventilation rates in commercial buildings specifies a minimum ventilation of 8 liter per second (L/s) per person for offices, using the standard's default value for occupant density. Based on a recent analysis, the projected practical benefits of increasing ventilation rates in U.S. offices to 15 L/s per person, in buildings with lower existing ventilation rates, include 0.6% to 1% increases in work performance and 10% to 19% decreases in sick building syndrome symptoms in 12 to 16 million workers, plus 7 to 10 million days of avoided absence. The associated total annual economic benefit ranges from $9 billion to $14 billion. The estimated annual energy and implementation costs were very small relative to the estimated benefits. For changes in ventilation rates in other types of buildings, such as homes and schools, no analyses were identified of the costs and benefits at the national level.
Better Control of Indoor Temperatures: Indoor temperatures in U.S. commercial buildings are often not precisely controlled. The Thermal Comfort Standard of the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) defines thermal comfort zones for winter and summer within which a majority of people are thermally comfortable. Many buildings are operated with the goal of maintaining temperatures within these comfort zones. As discussed in the section of this web site on performance and productivity, indoor temperatures also affect performance of office work, and performance is maximized with a temperature of approximately 21 °C to 23 °C. In offices, a large study indicates that as temperatures in the winter decrease below 23 °C, sick building syndrome symptoms diminish. Taken together, this evidence indicates an opportunity to improve overall thermal comfort, increase work performance slightly, and decrease sick building syndrome symptoms by avoiding winter work-time temperatures greater than approximately 23 °C in U.S. offices. Using data from a large survey of indoor office temperatures in the U.S., in most offices temperatures exceed 23 °C during at least a portion of winter work days. The benefits of avoiding winter temperatures above 23 °C were estimated. The estimated benefits included an average 0.2% increase in work performance in 40 million workers, an average 12% reduction in winter dissatisfaction with thermal comfort in 40 million workers, and prevention of 8 million cases of weekly sick building syndrome symptoms. The total estimated annual economic benefit was $3.4 billion with an annual implementation cost less than $0.4 billion.
Reducing Dampness and Mold: As indicated in the section of this website on dampness and mold, dampness and mold problems are common in homes, schools, and offices. Occupants of homes with dampness and mold have more respiratory health symptoms, more frequent asthma exacerbation, and more respiratory infections such as common colds. Based on a survey of approximately 1400 office workers, sick leave due to respiratory health effects is increased in offices with dampness and mold. Published analyses estimated that 4.6 million cases of current asthma, with an annual cost of $3.5 billion, and 8% to 20% of common respiratory infections, are attributable to dampness and mold in U.S. homes. Large reductions in dampness and mold are technically feasible, but due to economic constraints and other barriers a moderate 30% reduction is more realistic. Given estimates of the total impacts of dampness and mold in U.S. homes, the estimated benefits of a 30% reduction in dampness and mold in U.S. homes include prevention of 1.4 million cases of current asthma, saving $1 billion annually in health-related costs including mortality, morbidity (costs of medical care) and indirect costs (e.g., lost work and/or school days), and a 2% to 6% decrease in common respiratory infections. An estimated 23% of offices have dampness or mold. The estimated benefits of a 30% reduction of dampness and mold in offices include 1.5 million days of avoided absence per year, worth $0.5 billion per year in avoided lost work.
Improved Particle Filtration: Particle filtration in buildings can substantially reduce people's exposures to particles from both outdoor air and indoor sources. While the health effects of indoor-generated particles are poorly understood, higher concentrations of outdoor air particles are strongly linked to premature death and a variety of adverse health effects. Many U.S. homes have particle filters installed in the air handling systems associated with furnaces and air conditioners. These filters are often intended to protect heating and cooling equipment from build-up of unwanted materials on surfaces (e.g., heating and cooling coils, fan motors), but with low efficiencies for removing the small particles most important to health. Some homes have no particle filtration at all. Systems for removing small health-relevant particles in homes are becoming more readily available. Most U.S. commercial buildings filter the incoming outdoor air and the recirculated indoor air, but often the filters used have low particle removal efficiencies. Consequently, there appears to be a considerable potential to prevent premature deaths and reduce adverse health effects though improved particle filtration in buildings.
Other Opportunities: The estimates described in this web site of possible national-level benefits of improved IEQ serve as examples. There is a much larger set of likely opportunities, but in many cases with less supporting data.
Uncertainties: The estimates of the practical national-level benefits of improved IEQ have a high uncertainty, perhaps a factor of two or three, primarily because of the uncertain extent to which IEQ affects health, performance, and absence. Most of the estimates rely on analyses of the results of many studies, which reduce uncertainty. Because the underlying data are much more limited, uncertainties are higher for reductions in absence when ventilation rates are increased, for reductions in absence when office dampness and mold are decreased, and for decreases in SBS symptoms when high winter temperatures are avoided.
The estimates of benefits of improved IEQ account for the average impact of IEQ on health, performance, and absence. The benefits of specific actions will vary among buildings; for example, the benefits of increased ventilation rates are likely to be higher in a building with strong indoor sources of air pollutants than in a building with weak indoor sources of air pollutants.
Stakeholders and Barriers: There are a variety of barriers that make it challenging to fully capitalize on the opportunities for large benefits from improved IEQ. The evidence for large benefits was developed only recently and is not broadly recognized. Investments are required to achieve many of the benefits. People often fail to make investments even when the payback is large, particularly when the magnitude of benefits is uncertain. Also, the individual who needs to make the investment (e.g., a building owner) sometimes does not directly benefit from improvements in the health or work performance of the occupants of a building (e.g., tenants); thus, there may be little incentive to make the necessary investments. Sharing the benefits among building owners and tenants could provide the necessary incentives.
Comparison to Prior Estimates: The potential for large benefits had been predicted a decade or more ago but current data allow more accurate estimation of the magnitude of benefits and costs.