Determining the building airtightness using measurements of

CO2 Concentration


Project abstract

Building airtightness is defined as the resistance to inward or outward air leakage through unintentional leakage points or areas in the building envelope such as e.g. window frames or wall junctions. Airtightness is the fundamental building property that impacts infiltration and exfiltration (the uncontrolled inward and outward leakage of outdoor air through cracks, interstices or other unintentional openings of a building, caused by pressure effects of the wind and/or stack effect). One of the ways to determine the airtightness of the building is to use a fan, temporarily installed in the building envelope (a blower door) to pressurize the building. The other nonintrusive way is to determine it indirectly by using CO2 measurement. The CO2 measurement is a good indicator of occupancy, as long there is no other significant source of it which is the case in most buildings. Analysis of the CO2 level decays during vacant intervals provides the infiltration rate for building zones without mechanical ventilation [1]. Infiltration rate is measured in Air changes per hour unit, abbreviated ACPH or ACH.  Air change rate is a measure of the air volume added to or removed from a space in one hour, divided by the volume of the space.




The project execution is divided into the following mini projects. They could be studied independently (only certain mini project), sequentially (mini project by mini project) or could be divided between a team of students (every student one task), based on the students’ preferences.


Mini projects

  • To measure, monitor and collect CO2 level measurement LARES Zigbee setup consisted of ZBS-122 sensors, ZBR-100 router and ZBG-100 gateway with LabCon-SW could be used. The sensors are wireless and could be easily used for performing experimental measurements in different building zones (rooms). The goal of this project is to develop a user-friendly computer program, written in MATLAB or Python, used to determine building zone infiltration rate based on measurements of CO2 levels. The experiments will be performed in one of the zones of FER skyscraper building.


  • As an upgrade of the first mini project, for interested students, there is a possibility to continue working with the Zigbee setup by developing the Python routines for estimation of window openness. The performance of the routines will be tested on a back-up copy of FER skyscraper smart control system database. If the developed routines will perform well it is possible to integrate them into FER skyscraper smart control system.


Additional information

[1] Roulet Claude-Alain & Flavio Foradini (2002) Simple and Cheap Air Change Rate Measurement Using CO2 Concentration Decays, International Journal of Ventilation, 1:1, 39-44, DOI: 10.1080/14733315.2002.11683620