Conference Agenda

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.