Conference Agenda

In recent years, the adoption of sustainable building materials has become essential in efforts to combat global warming. As a result, the use of wood in public buildings has been increasingly prioritized. In the case of Japan, many public hot spring facilities were mainly constructed with reinforced concrete for earthquake resistance and ease of maintenance, there is now a noticeable shift towards wooden structures in these facilities. Wood plays a vital role in creating a warm and inviting atmosphere within hot spring facilities, offering bathers a sense of healing and relaxation. However, without effective humidity control, these environments can encourage the growth of decay-causing bacteria. This risk is present not only in the hot and humid summer months but also in winter, when the high temperature and humidity generated by the hot spring water can accelerate the deterioration of both wooden interior finishes and structural materials. Furthermore, this can lead to health issues for occupants due to the growth of wood-decay fungi and other harmful microorganisms. This study examines the risks of mold and wood decay in wooden and reinforced concrete hot spring facilities in a mountainous region of Shimane Prefecture, where heavy snowfall and high humidity persist during winter despite low temperatures. Findings reveal that, despite regular maintenance, sustained high humidity led to progressive decay in the wooden facility, necessitating major renovations within 12 years. In the concrete facility, temperatures of ≥25°C and humidity levels of ≥85% promoted bacterial decay 94.5% of the time. Enhancing ventilation and moisture control is crucial to mitigating these risks. These insights will help identify thermal environmental factors contributing to wood decay, aiding in the prevention of moisture damage in future facility construction and renovation.

Energy efficiency retrofits that include improved ventilation may reduce indoor radon concentration while those that only increase the airtightness of the building envelope above grade have the potential to result in increased radon. A field study of 24 townhouses in Edmonton, Alberta, was conducted to evaluate the impact of deep energy efficiency retrofits on indoor radon concentration in occupied homes. The energy retrofits included increased roof, wall and frost wall insulation, replacement of the gas furnace with a heat pump, rooftop solar and offsite renewables, and installing triple-glazed windows and heat recovery ventilators. Indoor radon concentration was measured using a continuous radon monitor in both the basement and on the upper floor of each dwelling for a one-month period prior to the retrofits, during March 2022, and after the retrofits were completed, during March 2024. Guarded and unguarded blower door testing was conducted both before and after the retrofits were completed for 12 of the study houses. The airtightness of the housing was increased by the energy retrofits, with the air changes per hour decreased from a median of 3.5 to 1.2 ACH for the guarded testing and from a median of 5.0 to 2.6 ACH for the unguarded testing. There was no consistent trend in indoor radon following completion of the energy retrofits: decreasing in 12 townhouses, remaining similar in 3 townhouses, and increasing in 9 townhouses. The median indoor radon concentration measured in the basement was 96 Bq/m3 pre-retrofit and 86 Bq/m3 post-retrofit. Health Canada recommends radon testing in houses if substantial renovations have been completed and mitigation for houses with radon concentration over the guideline value of 200 Bq/m3. These results suggest that the energy efficiency of existing housing can be improved while maintaining or decreasing the indoor radon for retrofits that include heat recovery ventilation.

The good news is carbon monoxide (CO) levels outdoors are now almost always under 1 ppm and rarely over 3 ppm. This is far below the EPA NAAQS limits of 9 and 35 ppm average for 8- and 1-hour exposures set in 1971 when CO levels were higher. The bad news is CO levels inside many buildings are now higher, even in some all-electric buildings, due to CO that occupants make and exhale 24/7 and CO they generate when frying, baking, or broiling food, burning candles or incense, and operating gas-powered equipment indoors such as forklifts. Over 100 epidemiology studies show average CO exposures as low as 1 to 3 ppm average over 1 to 8 hours associated with statistically significant increases in same-day mortality from many specific causes including heart attacks and from all causes. The latter increase by about 1% for each 1 ppm or interquartile range increase in CO, which is more than from particulate matter. Although the EPA never lowered its CO NAAQS, other authorities have recently lowered their CO limits based on these studies. We review indoor CO limits adopted in 2021 by the World Health Organization (allowing up to 3.5 ppm average for everyone, 60% less than its prior low limit), and in 2024 by the American Conference of Government Industrial Hygienists (allowing 15 ppm average for workers, 40% less than its prior limit) and a Dutch advisory board (allowing 7 mg/m3 average for workers, about 6 ppm, a 65% decrease). Given that CO dataloggers can record CO accurately in tenths of ppm for under $100, we recommend ASHRAE standards require indoor air monitoring of CO 24/7 and use ventilation to keep CO below the WHO limit. When paired with carbon dioxide monitoring, the ratio of (CO*100)/CO2 can distinguish exhaled CO from exogenous CO.