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The air renovation of a building should be controlled in order to ensure a proper level of indoor air quality while minimize heat losses. It is a crucial point for the future energy efficiency goals. However, air infiltration rate in buildings is a complex parameter which is influenced by several boundary conditions. Although a detailed dynamic analysis could be used to properly characterize the phenomenon, estimated values can be obtained from experimental methods, as Blower Door test and gas concentration-based approaches. Given that, the market provides affordable sensors which permit recording CO2 concentration, the present study has implemented those methodologies using CO2 as a gas tracer to estimate the air infiltration rate.
For the present study, CO2 concentration measurements have been carried out in a typical Spanish residential building. Weather data have been provided by a nearby meteorological station. Using data collected during unoccupied hours, the CO2 decay method has been implemented. Furthermore, Blower Door tests have been performed and compared with the CO2 concentration-based method.
Infiltration rate results using the decay method differ between different time periods in a considerable way, ranging between 0.08 and 0.49 air changes/hours. These variations are mainly due to differences in wind speed, wind direction and temperature gradient between the interior and the exterior of the building. Although these factors clearly influence the external air infiltration level, they alone are unable to describe in a complete way the air tightness of the building envelope due to the complexity of the phenomenon (building shape, local wind distribution and wind gusts). This paper aims to contribute enhancing awareness regarding infiltration field study and suggest a simple and not invasive methodology to obtain the n50 parameter useful as input for building models calibration.