Indoor Air Quality in Passive Houses
were a simple idea: construct a building that was well-insulated with a tight envelope, and the result was a very energy-efficient home. A proclaimed benefit of these homes, in addition to the energy efficiency, was improved due to continuous mechanical ventilation and filtered incoming air. Filtering the ventilation air only solved one issue, however. Many air pollutants in homes come from indoor sources. The goal of this study was to observe and quantify how passive houses were impacted by common indoor pollutants.
In this project, we measured fine particulate matter, carbon dioxide, carbon monoxide, ozone, nitrogen dioxide, total volatile organic compounds (TVOCs), and radon inside passive houses in Colorado and the surrounding areas. The homes were studied while unoccupied to determine a baseline condition, and then again while we performed a series of repeatable activities, like cooking and walking around. Bedrooms were also monitored overnight to determine if high temperatures or carbon dioxide build-up from respiration may have been an issue.
A pilot study was conducted in a passive house near Fort Collins in November of 2017. Results indicated that outdoor PM had little effect on indoor levels, while walking and cooking greatly increased indoor PM. TVOC levels appeared to be independent of any inside activities. CO2 levels were significantly increased by both activities, with cooking having a larger impact. Due to very low air exchange rates, CO2 and PM levels were slow to decay once elevated. In the bedroom, CO2 levels increased at night to above 1000 ppm. Overheating was not an issue in late fall, with an average temperature of 21.7°C and a maximum of 26.0°C. Relative humidity ranged from 12.2% to 34.2% with a mean of 25.3%. Overall, results showed generally good air quality that degraded during cooking. Thus, it was recommended to supplement ventilation with open windows or doors while cooking.
A was conducted in which indoor air quality was monitored in passive and tightly constructed homes in Colorado. Cooking tests resulted in 20-min average PM2.5 concentrations between 100 and 500 μg/m3, while no significant PM2.5 reduction was found between default ventilation and short-term boost. Additionally, the study found CO2 concentrations exceeded 1000 ppm in six of the ten tested homes.and formaldehyde exceeded the California OEHHA chronic limit of 9 μg/m3 in all buildings.
Ryan Militello-Hourigan cooking an egg in the passive house.
Air monitoring outside the house.
Air monitoring in the house.