Measuring Indoor Environmental Quality (IEQ) in a National School Property Portfolio

This thesis introduces a methodological approach for assessing Indoor Environmental Quality (IEQ) at an unprecedented scale in a large property portfolio to identify good and poor IEQ in buildings to inform design, asset management, maintenance, and evidence-based policy decisions. There is clear evidence that with deteriorating IEQ conditions, there is a decrease in human performance and their acceptability of the indoor environment. This thesis initially sought to find precedents for the influence of combined IEQ (lighting, temperature, relative humidity, acoustics, and indoor air quality) measurements on learning performance in schools and found none. No standards for measuring or characterizing this all inclusive IEQ in classrooms was found. In previous IEQ studies, there is no coherent guidance on representative placement of sensors (data loggers) and height to place a multi-variable sensor within a space.

The primary purpose of this thesis was to ascertain whether a one-point sensor measurement could be representative of the environmental condition across a space and where might be the best location to measure IEQ in many classrooms. Using the New Zealand Ministry of Education portfolio as a case study, physical measurements and observations were carried out in three typical case study classrooms, in three selected schools in Wellington. An array of sensors that simultaneously measures all five IEQ variables in a single device were deployed on the vertical walls and on the horizontal measuring plane in the case study classrooms during non-school days and school days in summer, autumn, and spring. One external sensor was positioned outside the classroom in a shaded walkway to monitor external environmental data and external weather data was also retrieved from the closet weather station.

The main conclusion is that for all five environmental variables, the relationship between the central horizontal plane and vertical wall sensors was consistent for approximately 80% of the time. This indicated that a vertical wall sensor can reliably predict IEQ levels at the centre of a classroom. This study concludes that a one-point sensor located on an unglazed vertical wall, where the sun is unlikely to shine and away from any sources of heat can strongly predict IEQ at the most frequently occupied parts of a space (the centre).

A one-point measurement provides an indication of what is happening in a room, but not necessarily all the variations (differences) across the room. The use of a one-point sensor gives a general indication of IEQ trends and patterns. It can suggest that IEQ highs are way too high or the lows way too low, or the range of extremes are too broad. It cannot pinpoint problem causes, or specific local issues, but is useful to triage good and poor IEQ in classrooms for early discrimination from hundreds or more classrooms of how to direct the maintenance or refurbishment programmes for large groups of school buildings. An additional level of information could be picked up better by using multiple sensors, building modelling or in combination with other qualitative methods such as survey of occupants. These findings can be used by researchers, architects, building scientist and policymakers to diagnose building performance in a national school property portfolio. The same process could be used in any large property portfolio to prioritize remediation works.