Conference Agenda

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Session Overview
Session 27: Thermal comfort studies
Thursday, 26/Aug/2021:
4:00pm - 5:30pm

Session Chair: Prof. Jørn Toftum, Technical University of Denmark
Location: Room 2 - Room 011, Building: 116

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4:00pm - 4:15pm

Factors influencing the perception of the thermal and visual indoor environment

Jørn Toftum1, Anders Thorseth1, Asta Logadottir2, Jakob Markvart3, Sophie Stofffer3

1Technical University of Denmark, Denmark; 2LOTA Engineering, Iceland; 3Aalborg University, Denmark

Earlier studies have documented significant effects on thermal sensation of the correlated color temperature of lighting (CCT). Generally, low CCTs induced a warmer thermal sensation than high CCTs at the same ambient temperature. However, most of these studies were carried out under ideal experimental conditions, i.e. with no disturbance from daylight, computer monitors or colored surfaces and with rather short exposure durations. The current study investigated if the association between CCT and thermal sensation would persist when subjects worked on computers, were exposed for longer duration and when the study population included older subjects whose vision may have changed with age.

The study was carried out in a climate chamber with controllable LED lighting and where CCT could be gradually changed.

Generally, the association between CCT and thermal sensation was weak and not significant, although at 22oC and with short-term exposure, the results indicated that high CCT caused a cooler thermal sensation. This association disappeared with longer exposure duration and when subjects worked on a computer. When they were not using a computer, the light was experienced as clearly more bright with increasing CCT. Comparison of responses to lighting exposure of the two groups of subjects with mean ages of 24 years and 44 years showed that there was no difference in their perceived thermal sensation when the CCT was changed. However, the older group of subjects could not distinguish differences in CCTs above 4000 K.

The findings suggest that the magnitude of the effect of lighting on thermal perception is rather modest and only visible under exceptional and tightly controlled conditions that do not mirror real buildings. However, the study supports that different domains of the indoor environment interact to some degree, but the strength of the interaction varies with the domain and with the type of perceptual outcome.

4:15pm - 4:30pm

Too Hot to Stay at Home: Residential Heat Vulnerability in Urban India

Aditi Agarwal, Holly Samuelson

Harvard University Graduate School of Design, United States of America

Recent climate trends show that India could suffer from deadly heat waves within a few decades. Combined with a growing urban population and mass production of affordable housing, this could sharply accelerate the demand for space cooling. India’s recently launched Energy Conservation Building Code - Residential (ECBC-R) or Eco Niwas Samhita 2018 uses a novel method for regulating energy efficiency. Specifically, this building code limits the total thermal transmittance of the envelope. This research considers and critiques this approach and focuses on indoor comfort and the severity of overheating during the summer months, in the hot-dry and warm-humid climate zones.

By using the outdoor running mean temperature, a comfort range is defined for the summer months (April-May-June), in the current climate and a medium emissions future climate scenario. We found that the code’s simplified approach has limitations, for example, requirements do not vary with climate zones within the country. On a typical cooling day, the same building materials that keep indoor temperatures within the comfort range in the warm-humid climate zone, lead to severe overheating in the hot-dry climate zone. Our analysis shows that soon (by 2030s) parts of the country are expected to be uncomfortably hot for over 74% of the time in summer. The code, however, is not adapted to future climate conditions. We found that a minimally code compliant building would need air conditioning 90% of the time in summer while a highly efficient iteration could reduce this need by a third, providing a big saving potential, in the hot-dry climate zone. Further, commonly used envelope assemblies are uncomfortably hot 77% (hot-dry) and 23% (hot-humid) of time in summer, on average. This analysis illustrates the vulnerability of current construction techniques to extreme heat and aims to avoid a long-term lock-in of inefficient, high energy consuming residential buildings.

4:30pm - 4:45pm

Experimental investigation of occupants’ thermal sensation under a personalized ventilation system

Peyman Ebrahimi Naghani1, Seyed Alireza Zolfaghari1, Mehdi Maerefat2, Jørn Toftum3, Seyed Mohammad Hooshmand1, Mostafa Izadi1

1University of Birjand, Iran; 2Tarbiat Modares University, Iran; 3Technical University of Denmark

By considering the importance of providing proper indoor environment conditions for occupants and also due to energy costs, one of the solutions for indoor local air-conditioning is Personalized Ventilation System (PVS). In this paper, the occupants’ thermal sensation was experimentally studied for body segments that are mostly affected by the PVS. The local sensation of head, chest, arm, and hand at two supply air temperatures of 16 and 32°C were investigated. Eight volunteer subjects participated in this survey. The subjects reported the most thermal satisfaction on their hands. Also, the arms were the segments with the coolest thermal sensation (-1.28, between slightly cool and cold). Results indicate that the head’s thermal sensation at both supply air temperatures was neutral and the hand was the only body part that experienced warm thermal sensation during the test. Also, by increasing the supply air temperature to 32°C whole body thermal sensation changed from -0.46 to -0.09 on the seven-point scale, which means that the cooling system worked properly for occupants’ cooling. In this system, cooling occurred at 32°C instead of the common 16°C supply air temperature, which results in energy-saving and decreases annual running costs.

4:45pm - 5:00pm

A field study on summertime overheating of six schools in Montreal Canada

Zihan Xie1, Chang Shu1, Ben Zegen Reich1, Lin Wang1, Daniel Brail1, Lili Ji1, Senwen Yang1, Xuechen Bai1, Radu Zmeureanu1, Michael Lacasse2, Liangzhu Wang1, Hua Ge1

1Centre for Zero Building Energy Studies, Department of Building, Civil and Environmental Engineering, Gina Cody School of Engineering and Computer Science, Concordia University, Montreal, Qc, Canada; 2National Research Council Canada

Due to global climate change, the world has been experiencing a significant increase in average temperatures and an increase in the frequency and intensity of extreme weather events such as heatwaves. The overheating problem in indoor spaces of buildings has become a concern to the comfort and health of building occupants, especially vulnerable populations such as the elderly, children, or the sick.

A field monitoring network consisting of rooftop weather stations and indoor sensors have been set up on 11 buildings of different types across Montreal as part of an NSERC research project. This paper presents the results of field measurements of indoor thermal conditions of six school buildings to assess the risks of summertime overheating. These six primary school buildings were built in 1930-1966 with a window-wall-ratio between 10-30% and no mechanical ventilation. The indoor dry-bulb air temperature, relative humidity, and CO2 concentration are measured by wireless indoor sensors. The weather conditions, dry-bulb temperature, relative humidity, solar radiation, rainfall, wind speed, and wind direction, are measured by rooftop weather stations.

Measurements presented in this paper are collected from July to September 2020, which includes three distinct time intervals: (a) during two heat waves, (b) during vacation when schools were closed and windows were closed, and (c) when schools reopened and windows were intermittently opened.

Data analysis shows that the indoor and outdoor temperature difference has a strong linear correlation with the outdoor temperature, observed for all school buildings. This correlation is influenced by the operation of buildings such as opening windows, closing blinds, and the micro-climate of its surroundings. Applying ASHRAE Adaptive model, these buildings show risks for overheating when the outdoor daily average temperature exceeds 20oC without natural ventilation and indoor temperature could sustain over the comfort threshold for a few days.

5:00pm - 5:15pm

Indoor environmental quality and global comfort: an in-field study in workspaces

Giuseppina Emma Puglisi, Giorgia Spigliantini, Niccolò Oggiani, Louena Shtrepi, Marco Carlo Masoero, Stefano Paolo Corgnati, Arianna Astolfi

Politecnico di Torino, Italy

The European standard EN 16798-1 specifies the minimum requirements to design and assess indoor environmental quality (IEQ) considering thermal, air quality, lighting and acoustics domains. However, a main drawback of the standard is that it is based on an objective evaluation approach (based on measurable variables) and does not account for the subjective perception of the occupants. Also, the standard does not assess global IEQ nor global comfort as a unique index that accounts for the interaction of all the physical domains.

To go beyond the available knowledge, this work contributes to test the metrics proposed in the standard relating them to the occupants’ subjective evaluations. Moreover, it integrates the different domains that build the global IEQ and comfort both at a methodological and analytical level. An in-field monitoring campaign was carried out involving workspaces such as laboratories and offices of ARPA headquarters in Aosta (Italy) across three weeks in summer 2020, with the objective to acquire objective physical quantities and to correlate them with the subjective perception of indoor environmental quality gained through repeated questionnaires. An insight about the possible approach to communicate IEQ and comfort feedbacks and metrics to the occupants was also investigated, in order to promote their awareness and engagement.

Preliminary results show that the occupants’ subjective perception can be predicted coherently by adopting the approach proposed in the EN 16798-1 in the case of thermal comfort, but conversely limitations emerge with regard to air quality, lighting and acoustics domains. Such result allows investigating the extent to which the environmental variables considered by the standard (e.g., the maximum sound pressure level for the acoustic comfort or the maximum CO2 concentration for the air quality) can be considered as best predictors of subjective comfort, thus the extent to which new parameters and assessment methods should be introduced.

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