Outdoor space design and its effect on mental work performance in a subtropical climate

Abstract

• 96 subjects did mental work in 4 outdoor spaces with surveys and environmental measurements. • Cognitive performance outdoors is comparable to or better than indoors in transitional seasons. • Thermal conditions influence mental work, which degrades fast when UTCI exceeds 32 °C. • Outdoor lighting preferences lean towards brighter environments than indoor office work. • Perceived workload mediates the relationship between environment and cognitive performance. Due to the stress resulting from high-density urbanisation, a premium is being placed on the restorative benefits of outdoor spaces for city dwellers. Outdoor spaces are increasingly being used as workplaces for tasks that have usually been performed indoors. However, the interrelationships among physical environmental parameters, perceived workload, and cognitive performance in outdoor spaces have not been studied in-depth. This study explores the suitability of outdoor urban spaces for short-term mental work during the transitional and hot-humid seasons in China's subtropical region. Four typical outdoor spaces in Shenzhen were selected to conduct questionnaire surveys and cognitive tests on a sample of 96 college-age participants. Concurrently, micrometeorological, illumination and acoustic environmental measurements were taken. The findings revealed that, firstly, in the transient season, working outdoors achieved similar or even better cognitive performance compared with indoors, with less perceived workload pressure, suggesting the feasibility and potential benefits of working outdoors. However, in the hot season, the subjective comfort, perceived workload and cognitive performance are all rather poor. Secondly, thermal conditions significantly affected outdoor work. Cognitive performance was superior outdoors compared to indoors when the Universal Thermal Climatic Index (UTCI) was within the range of 9 to 32 °C. However, this performance declines sharply when UTCI exceeds 32 °C. Similar trends are also observed for subjective comfort and perceived workload. Thirdly, lighting conditions also influenced comfort and performance, with participants preferring brighter environments (1000–2000 Lux) outdoors compared to indoor settings. Meanwhile, space design played a critical role in mitigating outdoor discomfort. Vegetation and shading elements, such as those in Patio Space, reduced thermal stress with an average UTCI reduction of 2 °C and improved satisfaction by 20 %, underscoring their importance in creating usable outdoor work environments. Moreover, perceived workload was found to be the mediator between physical environment and cognitive performance, with physical burden being the most influential indicator. The results provide actionable insights for designers, urban planners and policymakers to promote sustainable, comfortable, and productive outdoor environments in subtropical cities.