Part A: Assessing the performance of the COMFA outdoor thermal comfort model on subjects performing physical activity

2017

Int J Biometeorol

Given the predominant use of heat-retaining materials in urban areas, numerous studies have addressed the urban heat island mitigation potential of various "cool" options, such as vegetation and high-albedo surfaces. The influence of altered radiational properties of such surfaces affects not only the air temperature within a microclimate, but more importantly the interactions of long-and shortwave radiation fluxes with the human body. Minimal studies have assessed how cool surfaces affect thermal comfort via changes in absorbed radiation by a human (R abs ) using real-world, rather than modeled, urban field data. The purpose of the current study is to assess the changes in the absorbed radiation by a human-a critical component of human energy budget models-based on surface type on hot summer days (air temperatures >38.5 • C). Field tests were conducted using a high-end microclimate station under predominantly clear sky conditions over ten surfaces with higher sky view factors in Lubbock, Texas. Three methods were used to measure and estimate R abs : a cylindrical radiation thermometer (CRT), a net radiometer, and a theoretical estimation model. Results over dry surfaces suggest that the use of high-albedo surfaces to reduce overall urban heat gain may not improve acute human thermal comfort in clear conditions due to increased reflected radiation. Further, the use of low-cost instrumentation, such as the CRT, shows potential in quantifying radiative heat loads within urban areas at temporal scales of 5-10 min or greater, yet further research is needed. Fine-scale radiative information in urban areas can aid in the decision-making process for urban heat mitigation using non-vegetated urban surfaces, with surface type choice is dependent on the need for short-term thermal comfort, or reducing cumulative heat gain to the urban fabric.

Section: Field Testsmentioning

confidence: 99%

“…17, summing the energy streams towards and away from the body utilizing the COMFA energy budget model (Kenny et al 2009a;Brown and Gillespie 1986;Vanos et al 2012a).…”

Section: Energy Budget Analysismentioning

confidence: 99%

Section: Energy Budget Analysismentioning

confidence: 99%

See 1 more Smart Citation

The influence of surface type on the absorbed radiation by a human under hot, dry conditions

Hardin

2017

Int J Biometeorol

“…This would in turn reduce thermal discomfort from sensible heat fluxes as found in related shade studies (e.g., Antoniadis et al, 2015;Shashua-Bar et al, 2011). Further microclimate factors influencing heat stress and thermal discomfort-in addition to exchanges of solar radiation and sensible heat (via convection) discussed here-include evaporation and longwave emittance (Kenny, Warland, Brown, & Gillespie, 2009;Vanos, Warland, Kenny, & Gillespie, 2010), with metabolic activity increasing core and skin temperatures due to increased heat generation Yao, Lian, Liu, & Shen, 2007).…”

Section: Playground Design In Hot Climatesmentioning

confidence: 63%

Hot playgrounds and children's health: A multiscale analysis of surface temperatures in Arizona, USA

Landscape and Urban Planning

Middel

McKercher

et al. 2016

h i g h l i g h t s• A mismatch exists between remotely sensed and in situ urban surface temperatures (T s ).• The hottest T s in a Phoenix area neighborhood were found on playground surfaces.• Children are more vulnerable to the effects of heat stress and high T s than adults.• Shade of any type is found effective in reducing T s and improving thermal safety.• Data must be collected at the touch-scale for spatially accurate high T s mitigation. a r t i c l e i n f o b s t r a c tObjectives: To provide novel quantification and advanced measurements of surface temperatures (T s ) in playgrounds, employing multiple scales of data, and provide insight into hot-hazard mitigation techniques and designs for improved environmental and public health. Methods: We conduct an analysis of T s in two Metro-Phoenix playgrounds at three scales: neighborhood (1 km resolution), microscale (6.8 m resolution), and touch-scale (1 cm resolution). Data were derived from two sources: airborne remote sensing (neighborhood and microscale) and in situ (playground site) infrared T s (touch-scale). Metrics of surface-to-air temperature deltas ( T s-a ) and scale offsets (errors) are introduced. Results: Select in situ T s in direct sunlight are shown to approach or surpass values likely to result in burns to children at touch-scales much finer than T s resolved by airborne remote sensing. Scale offsets based on neighbourhood and microscale ground observations are 3.8 • C and 7.3 • C less than the T s-a at the 1 cm touch-scale, respectively, and 6.6 • C and 10.1 • C lower than touch-scale playground equipment T s , respectively. Hence, the coarser scales underestimate high T s within playgrounds. Both natural (tree) and artificial (shade sail) shade types are associated with significant reductions in T s . Conclusions: A scale mismatch exists based on differing methods of urban T s measurement. The sub-meter touch-scale is the spatial scale at which data must be collected and policies of urban landscape design and health must be executed in order to mitigate high T s in high-contact environments such as playgrounds. Shade implementation is the most promising mitigation technique to reduce child burns, increase park usability, and mitigate urban heating.

“…This is equivalent to an RPE of 12-13 ("somewhat hard"), that which is prescribed by the American College of Sports Medicine, which recommends 30 minutes of moderate exercise 4-7 times per week [16]. Each subject's HR range was based on their age and resting heart rate, using the Karvonen method to find target heart rate [17] at the set intensity.…”

Section: Physiological and Psychological Data Acquisitionmentioning

confidence: 99%

Modelling skin temperature of a human exercising in an outdoor environment

WIT Transactions on Ecology and the Environment

Warland

Kenny

et al. 2010

Skin temperature monitoring is an important component when estimating thermoregulatory responses due to heat exchange at the skin surface. The aim of this study is to improve the accuracy of mean skin temperature (T sk ) predictions in human thermal comfort models, specifically the COMFA (COMfort FormulA) outdoor model, in order to reduce errors in energy budget estimates associated with T sk . Field tests were conducted on 12 subjects performing 30 minutes of steadystate physical activity (running or cycling) on two separate occasions. The predicted thermal sensations (PTS) from the COMFA budget model using both actual (measured) and predicted (with model)T sk were compared at 5-minute intervals.Results indicate that the model over-predictedT sk throughout the exercise period. The root mean square error (RMSE) ofT sk of subjects running was larger than cycling, and increased throughout the 30 minute exercise session; hence, the model was less able to accurately predictT sk as metabolic activity increased. The Spearman's correlation coefficients (r s ) for actual thermal sensation (ATS) with both actual and predictedT sk thermal sensation scores were low, (r s =0.315 and 0.285, respectively). However, ATS votes correlated more strongly with predicted thermal sensation (PTS) scores in running tests. Added psychological and physiological variables when exercising outdoors make it inherently difficult to apply current thermal comfort (TC) models to exercising subjects. There is need for further studies regarding prediction of overall TC while exercising outdoors for use in urban design and planning, as well as adapting models to specific types of exercise.