Linking House Characteristics and Owner Perceptions to Measured Methane Emissions in California Homes with Natural Gas

The California Residential Methane Emission Characterization (CARMEC) is an ongoing research study funded by the California Energy Commission to gather data from a diverse sample of homes with natural gas appliances. The study included measurements of methane leaks from the gas infrastructure present in homes and from the usage of a wide range of gas appliances. We surveyed occupants of the sampled homes to understand their usage patterns and opinions about their gas appliances. This paper represents a preliminary analysis of methane measurements made in a sample of 61 California homes from Redding, Chico, Merced, Fresno, and the San Francisco Bay Area. Measurements include whole house quiescent leaks and from the meter set assemblies, and emissions from gas appliances pilot light (if present), sustained combustion and transient emissions from ignition and extinguishment of burners. For the analysis on any associations between methane measurements and occupant survey responses, we focus on the measurements of whole house quiescent leaks and emissions from cooking appliances. While our field team did not observe any significant gas leaks or combustion safety issues with any of the gas appliances measured, about 20% of occupants report smelling gas inside their home or near gas appliances. Kitchens and garages are the common locations where gas smell was reported. We found that a higher percentage of occupants reported needing to replace one or more of their gas appliances in older homes built pre-1980. We found an association between higher whole house quiescent leaks in older homes and homes with a crawlspace. In limited cases, the responses from occupant survey were helpful in explaining the variations in methane emissions measured.