Determine a methodology for calculating the needed fresh air

Abstract

By improving thermal properties and air tightness of buildings, there is a change of indoor air quality in buildings – without any ventilation (natural or mechanical) there is a significant deterioration of indoor air quality. In low-energy and passive houses about 80% of total energy consumed for heating is used to heat the fresh air needed for occupants. The aim of the paper is to determine a methodology for calculating the needed airflow rate (including fresh air) in an occupied room, based on carbon dioxide measurement and calculation, in order to maintain a comfortable level of indoor air quality. The calculated airflow rate should optimize the investment and the operating costs of HVAC equipment. In the work calculation methods used to determine the ventilation airflow rate are analyzed. A methodology for calculating the ventilation airflow rate for a room with people inside by using the measured values of carbon dioxide concentration is presented. The connection between carbon dioxide concentration and ventilation airflow rate is verified by experimental measurements. This methodology is applicable in Slovakia because it complies with all current standards. The result obtained by using this calculation method is almost the same with the results achieved from experimental measurements. To confirm the results, we present a case study of an office with occupants, in which the ventilation airflow rate calculation method is applied.