Analysis of Indoor Air Quality in a Naturally Venti-lated University Building, Determination of an In-door Air Quality Indicator

Abstract

The indoor environment is characterized by thermal comfort, indoor air quality, lighting, acoustics and others compo-nents. A pilot study was performed in order to figure out a venti-lation indicator. The study is focused on the search for the indica-tor, which can specify a minimum ventilation rate for office buildings and school buildings. How should ventilation system control perform – based on which pollutant? In the indoor air, there are many pollutants which might be subject of investiga-tion. The study continues and develops the results of Clear – up project implemented at the CTU during years 2008 – 2012. The indoor air quality is analysed and evaluated in an office building of a university based on the concentration measurements of chemical pollutants. The office building envelope has been re-cently retrofitted. The paper is focused on the question how the IAQ in an office is influenced by a natural ventilation rate and by a new retrofit-ted facade. The comparison of Czech, German and World Health Organization (WHO) standards is included. The main results are expressed by percentage frequency of the measured concentra-tions divided by permissible exposure limits (PELs). The aim of the manuscript is to find an indicator for a naturally ventilated office. The measurements were carried out in November and December 2014. The selected pollutants were measured: total volatile organic compounds TVOC, carbon dioxide and formal-dehyde. The measurements were carried out in three different standpoints. These standpoints were specially chosen in order to describe IAQ in the whole office and anticipate non-uniformity in pollutants distribution. The SF6 tracer gas was used to determine air change rate. The measurements were carried out by a photo-acoustic field gas monitor. Its measurement principle is based on the photoacoustic infrared detection method. The concentration decay method was used to determine the air change rate via nat-ural ventilation through the building envelope. The air change through building envelope was calculated according to SF6 con-centration and the air changes according to some selected pollu-tants were calculated. The boundary outdoor conditions were taken from measurements made by the Czech Hydro Meteorolog-ical Institute (CHMU) and the National Institute for Public Health (SZU) for the city of Prague location. The air change val-ues were given in a table. The manuscript showed the IAQ indi-cator. The paper shows the importance of boundary conditions (outdoor pollution conditions and indoor equipment) of the IAQ calculations and measurements. The manuscript is intended to generalize the obtained results. According to the standard [7], the ventilation rate is supposed to be 0.1 1/h. The ventilation rate through the facade and building envelope is 0.108 1/h but it is not sufficient. The sufficient ventilation rates were calculated accord-ing to different pollutants to the values 0.123 and 0.129 and 0.120. The ideal value is 0.13 1/h.