Reducing Climate-Change-Induced Heat Strain and HVAC Performance Loss With Circulating Fans
With the rate of climate change accelerating and predicted outcomes growing more dire, the authors examine the potential of air-circulating fans to mitigate increased occupant heat strain in heated-and-ventilated-only warehouses and improve the resilience of mechanical systems and maintain occupant thermal comfort in conditioned commercial buildings.
In 1990, the Intergovernmental Panel on Climate Change (IPCC), the United Nations (U.N.) body for assessing the science related to climate change, released its First Assessment Report,1 detailing the impacts human activities were having on atmospheric greenhouse-gas concentrations and tropospheric air temperature. The report predicted global mean air temperature would rise by an average of 0.54°F (0.3°C) per decade in the 21st century, or 5.4°F (3.0°C) by the year 2100, an outcome that would be devastating for the environment and many of the world’s most vulnerable populations, which would suffer the effects of more frequent severe-weather events, sea-level rise of up to 3.3 ft (1 m), and food insecurity.
Flash forward to 2021 and the release of IPCC Working Group I’s contribution to the Sixth Assessment Report, which the U.N. secretary-general called a “code red for humanity.”2 While international treaties such as the Kyoto Protocol and the Paris Agreement were designed to cap mean-temperature increase at 2.7°F (1.5°C), the most likely greenhouse-gas-concentration trajectory adopted by the IPCC, the intermediate representative concentration pathway (RCP) of 4.5, sees a mean-temperature increase of up to 6.3°F (3.5°C) by the end of the century.3 In short, it is becoming increasingly clear that the 2.7°F (1.5°C) target will be exceeded, and it could happen as soon as 2050.3
This article will examine the predicted performance of buildings at significant risk from climate change and illustrate how the use of circulating fans can reduce cooling demand in conditioned buildings and heat strain in unconditioned ones under increasingly demanding climatic conditions.
Contextualizing Global Impacts and Existing Works
One of the greatest communication challenges in climate science is “consensus gap,” or the dissonance between analytical, scientific, and numerical effects of climate change (e.g., rise in mean temperature) and more human, contextual, and observational impacts of climate change (e.g., seasonal temperature, drought). Researchers at ETH Zurich leveraged connections between what populations subjectively know about and associate with their current climates to underscore the dramatic changes that will occur under the RCP-4.5 scenario by 2050, selecting 520 cities around the world and applying statistical models to 19 independent bioclimatic variables to determine the cities’ best future climatic analog.4
Distilling the results of the ETH Zurich study, Table 1 shows the future climatic analog of cities in 15 climate zones (CZ) used in U.S. Department of Energy (DOE) reference-model simulations and in ANSI/ASHRAE Standard 169-2021, Climatic Data for Building Design Standards.5 For context, 2017 annual heating degree-days based on 65°F (HDD65) and 2017 annual cooling degree-days based on 50°F (CDD50) from the ASHRAE Climatic Design Conditions database are given.
|Las Vegas, Nev.||3B||1,975||7,249|
|San Francisco, Calif.||3C||3,779||1,835|
|Future Climatic Analog||Future CZ||HDD65||CDD50|
|Rio de Janeiro, Brazil||1A||-106||-391|
|Kuwait City, Kuwait||1B||-201||1,808|
|El Paso, Texas||3B||-1,656||1,874|
|San Francisco, Calif.||3C||-926||-233|
|St. Louis, Mo.||4A||-1,518||1,017|
|Kansas City, Mo.||4A||-2,450||1,166|
|Salt Lake City, Utah||5B||-2,038||1,474|
|2% DB (°F)||54.9||57.3||64.6||71.7||81.2||84.5||91.3||90.2||86.6||72.2||59.8||53.6|
|2% MCWB (°F)||50.7||49.5||52.5||57||61.9||64.6||68.4||67.6||63.9||58||55.2||50.5|
|2% DB (°C)||12.7||14.1||18.1||22.1||27.3||29.2||32.9||32.3||30.3||22.3||15.4||12.0|
|2% MCWB (°C)||10.4||9.7||11.4||13.9||16.6||18.1||20.2||19.8||17.7||14.4||12.9||10.3|