Testing of a Tracer Gas Based Measurement Procedure to Assess Air Change Rates in Buildings

Buildings energy audits ask for a thorough analysis of the audit object. According to the series EN 16247, all the factors affecting actual energy consumption must be assessed and estimated. One of the hardest contributions to be quantified at this stage is air change rates of buildings, particularly when no mechanical air supply system is installed. In this case, just air leakages through the external envelope and users behavior (e.g. opening of doors and windows) will determine the actual figures of air change rates. As a consequence, no direct measurement can be made. Among the indirect measurement approaches, the procedure using the decay of indoor carbon dioxide concentration provided good results, as described in literature. However, a number of disturbing factors must be considered, because they affect the transient behavior of air exchange between indoor and outdoor. As a consequence, the experimental setup that must be used should be made up of a kit of sensors, and the concentration decay must be evaluated with respect to the actual behavior of related parameters, such as outdoor air pressure and wind speed. This paper will provide more insights into the possibility of developing a testing kit for the energy auditor, so that she/he can evaluate air change rates of buildings through quick on-site surveys in the audited object, and then use the information thus collected as an input for the energy audit process. Such a challenge requires the development of a quite cheap, easy to install and low invasive monitoring kit, which is based on state-of-the-art wireless and low power monitoring technology. In addition, data analyses must be quick and partially automated. Finally, a preliminary test performed in a room of the Engineering Faculty at the Università Politecnica delle Marche in Ancona (Italy) will be reported.