For many of us, we’ve grown up surrounded by family members that have told us not to go outside in the sweltering sun wearing dark clothing. Instead, light-colored clothing was usually advised. Why? The answer was always the darker the clothing, the greater the absorption of heat, essentially making you feel hotter. Their idea was that lighter clothing, in addition to a delicate fabric, elicits the visual of airiness, coolness, and breeziness. However, according to recent scientific studies, this isn’t the complete story or maybe not even the correct one.
When the sun is shining on a hot summer’s day, a combination of bright light and radiant heat is emitted. This sunlight consists of a mixture of wavelengths that include infrared, visible, and ultraviolet light. Light colored clothing reflects most of the visible wavelengths which, in turn, absorbs less heat. On the contrary, darker or black clothing absorbs more wavelengths, absorbing more heat, hence making the clothing warmer to wear. Although darker clothes are known to absorb more heat, this doesn’t necessarily mean that the heat will be transferred to the person wearing the clothes.
A study focusing on why Bedouins in the Sinai desert wear black robes, researched whether black robes help the Bedouins minimize solar heat loads in an extreme heat environment (Shkolnik et al., 1980). In order to investigate this, researchers measured the net heat gain by radiation, heat loss by convection, heat loss by evaporation, heat storage, and metabolic heat production of a single male participant standing facing the sun in the desert in four different types of colored clothing: a black Bedouin robe, a white robe similar to the Bedouin robe, a tan army uniform, and shorts. It was found that, although the black Bedouin robe absorbed 2.5 times more radiation than the white robe and 1.5 times more than the tan army uniform and shorts, the amount of heat gained by the participant was the same regardless of clothing. The additional heat absorbed by the black Bedouin robe was lost before it even reached the participant’s skin. This is most probably due to the Bedouin’s robes being loosely fitted, allowing for cooling by convection. This study demonstrated that regardless of color, heat gain was the same for loose fitted clothes. However, since the study was only done on one person, we must be cautious about the interpretation of these results.
Another study researching coat color and solar heat gain in animals found that the relation between coat color and solar heat gain is greatly varied (Walsberg, 1983). It was originally assumed that birds or mammals with darker plumage or coating experienced greater heat loads when exposed to solar radiation. However, after further research, empirical analyses demonstrated that the results are quite variable. Darker coats may result in an increased or decreased solar heat load depending on the organismal and environmental properties of the animal, which are completely independent of coat color. Furthermore, animal coat color and structure are very rarely uniform, making it difficult to conclude any relation between coat color and solar radiation.
Although more research is needed to understand how the color of the clothing affects heat gain in humans, the limited results suggest that the color of clothing may not be as major a factor as previously suggested. Lots of factors are also likely to be important for heat gain including the thickness and type of clothing (Palca, 2014). Until more experimental data is available to decide if wearing light-colored clothes in hot weather is better than wearing darker clothing, I will wear short pants and loose-fitting short sleeve tops in whatever color that is clean and available in my closet. Lastly, don’t forget to enjoy the sun!
Written by Rosemarie Majdalani and edited by Aldrin Gomes
References
Palca, J. (July 25, 2012). Summer Science: Clothes Keep You Cool, More or Less. http://www.npr.org/2012/07/25/157302810/summer-science-clothes-keep-you-cool-more-or-less
Shkolnik, A., Taylor, R. C., Finch, V., & Borut, A. (1980). Why do Bedouins wear black robes in hot deserts? Nature, 283, 373-375. https://doi.org/10.1038/283373a0
Walsberg, G. E. (1983). Coat Color and Solar Heat Gain in Animals. BioScience, 33(2), 88-91. https://doi.org/10.2307/1309169