Improving energy management of buildings is among the most promising application areas of new technology for sustainable living. The Pervasive Data Science Group of the University of Helsinki is experimenting with thermal cameras to gather fine-grained information for use as actionable feedback to heating, cooling and ventilation (HVAC) devices in shared living spaces. The idea is to develop solutions that go beyond reducing energy usage and can balance between living quality and overall energy consumption.
As a first step in this direction, they have conducted a feasibility study about using thermal imaging to estimate changes in comfort. Climate factors, such as exposure to sunlight, can influence thermal sensation and personal comfort level in a room by affecting the extent of thermal radiation seeping through into the room. To assess whether thermal imaging can indeed capture these factors, an office room shared by four employees and occasional visitors was monitored for three weeks. A Caterpillar CAT S60 phone with an integrated FLIR thermal camera was set up to take thermal images every four minutes, and temperature statistics from the images were compared to data provided by the Finnish Meteorological Institute (FMI). The results were promising, demonstrating how the influence of external climate factors, such as sunlight, can be captured using thermal imaging. In particular, a significant correlation was found between cloud cover statistics and temperature statistics extracted from thermal imaging output.
To understand how thermal imaging measurements correlate with the occupants’ perceptions, as part of the feasibility study the participants were asked to fill in daily surveys about their level of comfort and factors that could influence it. The preferred temperature is a subjective metric that varies from one person to another. Seven-point Likert scales were used for both thermal sensation (“very cold” – “very hot”) and comfort (“highly uncomfortable” – “highly comfortable”). The participants were also asked about the clothes they were wearing, how long they spent in the room, whether any windows or doors were open, and whether there were other events that may have affected their comfort. The results showed that comfort varied across the participants and that different areas of the room were exposed to differing amounts of thermal radiation, motivating the need for solutions that can separately analyze factors affecting thermal comfort of individuals in shared spaces.
Motivated by the promising results of the feasibility study, the team is continuing research into developing methods for assessing thermal comfort using thermal imaging. The primary focus is currently on developing methods for separating people from the thermal images and characterizing thermal radiation for different regions of the space being monitored. The feasibility study was supported by HIIT and the work is continuing through other funding sources.