Cool Walls vs. Cool roof.. which one is cooler?

Cool Walls vs. Cool roof.. which one is cooler?
By Alejandra Aguilera

https://pubs-acs-org.tamiu.idm.oclc.org/doi/pdf/10.1021/acs.est.8b00732?download=true

An increase of urban areas around the world has been noticed throughout the years. As cities are growing, the contamination on Earth increases as well. An example of these are the higher temperatures caused by the life style of the population, which in big cities is known as urban heat island effect (UHIE). A phenomenon in which urban areas are warmer than rural areas.  UHIE can affect the environment by increasing urban ozone concentrations and amount of energy used to maintain places at cooler temperatures as well as causing deadly diseases to humans. A study conducted in Los Angeles, California showed the effects of adding materials (asphalt concrete) with high solar absorbance to the walls and/or roof of buildings. To determine which option would create lower temperatures around the city. Researchers used Weather Research and Forecasting model version 3.7 (WRF) to simulate different weather temperatures. The study showed how cool roofs would lower the temperature at 20:00 hrs whereas cool walls at 14:00 hrs and 20:00 hrs; as there is more time of the day where sunrays hit buildings horizontally. This study would advance environmental sustainability by lowering the amount of energy that people use daily to maintain lower temperatures at home. In the same way, ozone concentrations would decrease and with it less smog would be noticed in cities. A trait-off found was the solar reflection of walls towards pedestrians at late afternoon which could cause glare and reducing their thermal comfort.

Reference

Zhang, J., Mohegh, A., Li, Y., Levinson, R., and Ban-Weiss, G. 2018. Systematic Comparison of the

Influence of Cool Wall versus Cool Roof Adoption on Urban Climate in Los Angeles Basin.

Environ. Sci. Technol. pp A-J