Cooling Bakersfield: The Materials Behind the Urban Heat Island Effect

Overview

Bakersfield experiences over 60 days a year with temperatures above 100°F. I tested five common urban surfaces (asphalt, concrete, white tile, grass, artificial turf) to see which has the biggest impact on the Urban Heat Island effect and public contact-burn risk. I predicted asphalt and turf would reach the highest temperatures due to low albedo, that concrete's high thermal mass would cause it to retain heat the longest, and that natural grass would not peak as high as turf because of evapotranspiration. A 250W infrared bulb simulated the Bakersfield sun. I used a high-albedo foil thermal mask to remove surface area as a confounding variable, standardizing a heated footprint of 6”x6" for all samples. I calibrated the infrared thermometer for emissivity based on the material. Each sample received 15-minute heating and 15-minute cooling cycles. I also conducted a 120-minute Phase 2 study that investigated concrete's thermal lag. To assess the public safety risk, I analyzed my results against skin contact burn thresholds referenced in NASA and ASTM C1055 policies. Both artificial turf and asphalt exceeded that danger limit. Turf peaked at 164.0°F ±3.21 SEM and was 14.3% hotter than asphalt (143.5°F ±3.94 SEM). During the “night time” cooling phase, concrete loses only 0.40°F per minute, and explains why heat lingers after sunset. Natural grass benefits from evapotranspiration to stay cool (102.9°F ±5.26 SEM). My study shows that replacing natural grass with artificial turf to conserve water unintentionally increases daytime burn risk. Phase 2 testing demonstrates that concrete contributes to nighttime UHI warming. Phase 3 consisted of prototyping a high-albedo and low heat retention infill for artificial turf and testing the prototype against standard turf while following the same methods of Phase 1 . This alternative infill drastically lowered turf’s average peak temperature by 48.3°F. High-albedo materials and evapotranspiration through native xeriscaping are effective tools for urban planners when considering both water conservation and public safety.

Competition history

• CSEF 2026 Environmental Engineering (Track 2) (Junior Division) · Entry J-12-07

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