Revisiting the Comfort Parameters of ISO 7730: Measurement and Simulation

With the trends of comfort modelling moving more towards the application of Adaptive Models; [1, 2]. The influences of several parameters evaluating thermal comfort from the traditional ISO7730 standard seem to have dropped out of the equation. The proposed work considers the conventional ISO7730 standard as conservative in its calculation, however extremely useful, in cases where actual measurements of spaces are considered [3]. Measurements from a comfort cart built according to ASHRAE-55 standards [4] together with thermal imaging temperatures of an interior space are analysed. In doing so, an ISO 7730 thermal comfort assessment is conducted. Applying the CBE –ASHRAE Thermal Comfort Tool (2004) allows for specific time periods of discomfort from real measurements to be analysed [5]. A house in Darwin, Australia, where high dry-bulb, mean radiant (surface) temperatures and humidity, is studied. The analysis comprises the alignment of the Comfort Tool results to match the thermal comfort cart measurements. From a validated result of simulation conditions matching those of measurement a retrofitting analysis takes place. Here the parameters of the ISO 7730 Comfort Model, such as MRT, shading of glazing systems to reduce interior surface temperature, air velocity, and the cooling of dry-bulb temperatures are all explored. This research utilises real measurements together with a well-known thermal comfort tool ASHRAE-55. Through the application of a thermal comfort cart as well as thermal imaging a comprehensive set of data is accomplished for. The comfort cart measurements are processed to yield the ISO-7730 comfort indices. The ISO standard calculation yields the Predicted Percentage Dissatisfied (PPD) and other parameters such as MRT are provided in this calculation. These results serve as the guide to validate and fine-tune the ASHRAE 55 Comfort Tool inputs until the simulation outputs matches the measured result. The validation of the simulation model was performed using the (CV RMSE) method in accordance with the ASHRAE Guideline 14-2014[6]. The Comfort Tool has a sub-routine for MRT calculation. The simulated results are once again compared with the ISO-7730 measured outputs from the comfort cart. The innovation rests in applying the comfort tool to achieve informed decision-making that can improve comfort conditions. For example, shading the glass from direct heat gain, thereby reducing the surface temperature substantially. Other solutions may consider applying radiant cooling systems for the ceiling and floor that will reduce the overall mean radiant temperature. Results indicate that the application of radiant systems in a hot humid climate are effective in improving comfort. In particular, the idea of cooling interior ceiling, floor and possibly wall surfaces through hydronic systems is explored [7]. The introduction of lightweight capillary hydronic matts (German and Japanese manufacturers) integrated with gypsum drywall construction or tiled floors as a possible cooling solution is proposed. Surface temperature levels that are between 24-26◦C and well above dew point (2-3◦C) indicate promising results for improved comfort in these environments. Furthermore, radiative conditioning, for leaky and poorly insulated houses, offers an improved energy cost benefit when compared to convective air conditioning systems.