Surface Temperature ≠ Heat Stress

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During summer, the importance of surface choice in managing heat stress is more apparent than ever. Well-maintained natural grass remains the gold standard for thermal comfort. Its ability to cool itself through evapotranspiration, combined with high surface reflectivity and low thermal mass, provides a naturally regulated environment for sport and outdoor leisure. However, not every field can be irrigated or maintained at this level.

To understand heat stress, it is important to realise that not all heat feels the same.

Imagine standing in a dry desert at 38°C (100°F) with a breeze , it may feel intense, but your sweat can still evaporate and help cool your body. Now compare that to being in a rainforest at 30°C (86°F) with 90 percent humidity, suddenly, your ability to cool down is compromised, your sweat cannot evaporate, and your core temperature rises faster. This is the critical difference between temperature and heat stress.

That is why the Wet Bulb Globe Temperature (WBGT) is used in sport and other outdoor actives (including construction) and related metrics to assess heat risk. This method incorporates temperature, humidity, wind speed, solar load, surface type, and clothing into a single actionable measure.

Through extensive research at TenCate, we have found that surface design plays a pivotal role in this equation. Te results are conclusive: rubber infill systems, particularly black SBR crumb, consistently create the worst thermal conditions for players and users. These systems:

  • Absorb more solar energy due to their dark colour and low albedo
  • Reach extreme surface temperatures in excess of 70°C (158°F) in direct sun
  • Retain heat due to high thermal mass and release it slowly over time
  • Maintain elevated mean radiant temperature, which increases body heat load
  • Continue radiating heat well into the evening, long after air temperatures drop

This does not mean these fields are inherently unsafe, but it does mean that field operators and coaches must actively monitor heat stress risk and apply appropriate mitigation protocols. These may include in extreme conditions altering training times, using shade, applying water, allowing extended breaks, and strictly following sport-specific heat guidelines.

Heat stress artificial turf

 

The good news is that modern turf systems can significantly reduce heat stress exposure through smart design. At TenCate, we have developed and validated multiple effective interventions, including:

  • Yarns with lighter colours (and reflective additives) to reduce solar gain
  • Alternative systems without infill or non-rubber infills that do not retain or radiate heat
  • PivotCool cooling layers that retain water and mimic the cooling effect of moist grass
  • Shockpads and engineered bases that buffer thermal energy and reduce surface temperature
  • Integrated water management systems to enhance passive cooling performance
  • and many others… some very exciting to be published soon!

Our testing includes both laboratory-controlled evaluations and real-world field measurements across climates. We monitor WBGT, surface and radiant temperature, skin temperature, and overall heat stress impact, using this data to guide system design.

The takeaway is simple: some synthetic systems can now closely match the thermal performance of well-irrigated grass fields, but only when the right turf system; materials and configurations are applied.

Do please ask me for more information or the data

As summer temperatures remain high, these details matter more than ever. Surface design is not just about performance or durability AND not all turf is equal some are “literally” cooler than others!

Tags: heat stress, surface, temperature
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