Non-Intrusive Measurements to Incorporate the Air Renovations in Dynamic Models Assessing the In-Situ Thermal Performance of Buildings

Abstract

This paper reports the analysis of the feasibility to characterise the air leakage and the mechanical ventilation avoiding the intrusiveness of the traditional measurement techniques of the corresponding indicators in buildings. The viability of obtaining the air renovation rate itself from measurements of the concentration of the metabolic CO2, and the possibilities to express this rate as function of other climatic variables, are studied. N2O tracer gas measurements have been taken as reference. A Test Cell and two full size buildings, with and without mechanical ventilation and with different levels of air leakage, are considered as case studies. One-month test campaigns have been used for the reference N2O tracer gas experiments. Longer periods are available for the analysis based on CO2 concentration. When the mechanical ventilation is not active, the results indicate significant correlation between the air renovation rate and the wind speed. The agreement between the N2O reference values and the evolution of the metabolic CO2 is larger for larger initial values of the CO2 concentration. When the mechanical ventilation is active, relevant variations have been observed among the N2O reference values along the test campaigns, without evidencing any correlation with the considered boundary variables.