PERC commissioned a study to investigate the impacts of vent-free gas products on indoor air quality (IAQ) in residential energy conservation structures, specifically energy-efficient homes. Such homes are usually characterized by low air exchange rates with outdoor air, and high insulation values. Modeled indoor air quality levels of five combustion-related chemicals, including carbon monoxide (CO), carbon dioxide (CO2), nitrogen dioxide (NO2), oxygen (O2), and water vapor (H2O) were compared to nationally- and internationally-recognized IAQ guidelines and standards. This research is built upon existing research and modeling tools that have a proven track record of predictive power for unvented gas heating appliances. These appliances include gas logs, fireplace systems, fireplace inserts, free-standing gas stoves, and heaters, which collectively are referred to as “unvented” or “vent-free” heaters.
The results of the current study indicate that the use of vent-free gas heating appliances in energy conservation homes does not result in adverse indoor air quality (IAQ) impacts in nearly all cases for each of the DOE Heating Regions for which simulations were conducted. The work in this current study applies to “low-rise” residential structures, focusing primarily on detached single family homes.