Respiratory infection risk based ventilation and room conditioning design method with year-round thermal comfort control in modern office buildings

Abstract

The new decade will be a major challenge for built environment to satisfy building users and owners demands for superior IEQ in the work environment and tackle infection risk issues brought by SARS-CoV-2 pandemic. We collected thermal comfort and IAQ data from modern Estonian office buildings showing that improvements are needed in whole chain of the HVAC science, engineering and manufacturing because current solutions in these buildings have led to many complaints of draught and readjustments of supply air temperature have typically compromised energy performance. To achieve Category II or I IEQ, more systematic design methodologies are needed. Additionally, ventilation rate and air distribution dimensioning based on respiratory infection risk has to be taken into use as a complementary method of existing ones for office space AC and ventilation design, where both net floor area and occupant number define the required ventilation. Based on air velocity and temperature (operative, supply air and local) measurements conducted in five office buildings a new IEQ design methods were developed to satisfy the thermal comfort indices leading to low occupant complaints and not compromising energy performance at the same time. In well ventilated Category I and II office spaces, control of draught risk is an extensive design task for which new methodology was developed. Our method focuses separately on IEQ parameters during heating, cooling and midseason, from which the latter one is the longest and the most dominating one. The design method is presented by connecting thermal comfort and infection risk with ventilation rate. Infection risk based air flow rate selection diagram and corresponding air velocity diagrams for an open plan office and 3-person room showing the possibilities to size ventilation for the event reproduction number of R = 0.5 were constructed.