A prior study  estimated that 21% (confidence limits of 12% to 29%) of current asthma, defined as having asthma symptoms or requiring asthma medication in the past year, was attributable to dampness or mold in homes. This estimate was based on statistical analyses of the results of ten studies published in the refereed archival literature that investigated how the prevalence of current asthma differed between occupants of homes with and without dampness or mold. Additionally, this estimate relied on the population-weighted average prevalence (47%) of dampness or mold in seven studies of U.S. homes. An estimated 21.8 million persons in the U.S. had asthma in the 2001 to 2005 period , thus, the 21% (12% to 29%) reduction in current asthma predicted if dampness in homes was eliminated translates to 4.6 (2.7 to 6.3) million avoided cases of current asthma. The associated annual economic benefit of this reduction in current asthma was estimated to equal $3.5 ($2.1 to $4.8) billion , primarily from reductions in medical care costs. A more practical 30% reduction in dampness and mold in homes translates to prevention of 1.4 million cases of asthma with an economic benefit of $1 billion annually.
Another prior study  analysed the results of 19 studies published in the refereed archival literature and estimated that 8% to 20% of common respiratory infections are attributable to dampness and mold in U.S. houses. A 30% reduction in dampness and mold translates into a 2% to 6% reduction in common respiratory infections. The associated economic benefits have not been estimated.
Compared to homes, less information is available about the health effects of dampness and mold in work places. The available data were reviewed by Mudarri and Fisk . They concluded that the evidence of increased respiratory health effects in offices and institutional buildings with dampness and mold was reasonably robust. Based on a survey of 1400 office workers , the occupants of the 23% of office buildings with dampness and mold have 30% more sick leave due to respiratory health effects than the occupants of office buildings without dampness and mold. From a 30% reduction in dampness and mold in U.S. offices, Fisk et al. , projected 1.5 million days per year of avoided absence in U.S. office workers. Using the average daily cost of salaries and benefits for office workers as the value of a day of absence, the annual economic benefit is approximately $0.5 billion.
The amount that dampness and mold can be reduced in U.S. homes and offices is uncertain and the estimates described above assumed a 30% reduction. We have the knowledge and technical capabilities to reduce dampness and mold in buildings by a large percentage; however, real-world reductions in dampness and mold are constrained by poverty, a lack of understanding of the consequences, the lack of incentives for improvements in rental housing, and other factors. The estimate that a 30% reduction in dampness and mold is practical and achievable is based on professional judgement. The results presented here can be scaled for other percent reductions in dampness and mold.
The implementation costs of retrofitting and remediating existing buildings to achieve reductions in dampness and mold may be considerable, given the necessary measures; e.g., repairs in roofs, building envelopes, and plumbing systems to reduce water leaks, and changing the way thermal insulation and air and moisture barriers are used in some building envelopes. Data for estimating the implementation costs were not identified. Consequently, the benefit estimates presented in this web site do not account for the implementation costs. The estimates also do not include several potentially large economic benefits associated with reduced dampness and mold, including reduced costs for repairing or replacing moisture-damaged building material, for mold remediation, and for health care for health effects other than asthma. The costs of improving design and construction practices in new construction, as needed to reduce dampness and mold problems over time as the building stock changes, would likely be much less than the cost of reducing dampness and mold through remediation of existing building problems.