Estimation of space heating CO2 emissions based only on CO2 fluxes observations

Heating buildings is a significant contributor to CO2 emissions in cities located at mid- and high-latitudes. This study aims to enhance our understanding of the average daily cycle and interseasonal variability of CO2 emissions from space heating. To achieve this goal, we have developed a methodology solely relying on observations to identify the contribution of space heating to CO2 fluxes measured in the urban inertial sublayer. This method offers two main advantages. Firstly, it allows for the estimation of space heating contribution with high frequency, facilitating the analysis of its daily cycle. Secondly, our estimation is independent of other methods that do not rely on observations, such as modeling or fuel-consumption based approaches. Our methodology was developed using original CO2 flux data measured at rooftop level. Utilizing such data raises theoretical questions. However, the results demonstrate that with adapted processes (non-rotation of data and the exclusion of data with excessively high absolute vertical speeds), the measurements are entirely valid. Our estimation is consistent with estimations made using established methods, such as numerical modeling with the urban canopy model TEB, Heating Degree Days, and gas consumption methods. •Measurements of CO2 fluxes at rooftop level require specific processes.•Fluxes measured at two levels are used to derive CO2 emissions from space heating.•CO2 emissions from space heating are estimated sub-day using only observations.•Our estimates agree well with other methods: gas consumption and heating degree days.