On This Page:

The latest ...

The Heat Effects [preface]

 - Sports Illustrated: "Sports and Global Warming"
- The New York City Study
- The University of Missouri Study
- The Utah Study
- The Texas Study
- Recommendations of the New York Study

The latest ....

ABC News Video Report

Lee DaSilva Field

Madera South High School, CA

This item reports on the delay of the starting time for a game to be played on artificial turf due to the heating of the field. The report refers to a temperature of 120 degrees F recorded at 5 PM. The coach of the team is shown saying that they will be having misting and cooling apparatus on the sidelines. The product is mentioned as being FieldTurf. Go here for the full report:

http://ww2.abc30.com/global/video/popup/pop_player.asp?clipid1=1715386&at1=News&vt1=v&h1=Artificial+Turf+Impacts+Football+for+Madera+South+High+School&d1=139400&redirUrl=www.abc30.com&activePane=info&LaunchPageAdTag=homepage&playerVersion=1&hostPageUrl=http%3A//ww2.abc30.com/global/video/popup/pop_playerLaunch.asp%3Fclipid1%3D1715386%26at1%3DNews%26vt1%3Dv%26h1%3DArtificial+Turf+Impacts+Football+for+Madera+South+High+School%26d1%3D139400%26redirUrl%3Dwww.abc30.com%26activePane%3Dinfo%26LaunchPageAdTag%3Dhomepage&rnd=37746125


Some August temperature readings around Boston, Massachusetts

Sudbury Cutting Field [on Mass. Route 27]
August 28, 2007, 11:45 AM, partly cloudy 
Ambient: 79 
Asphalt: 116 
Turf: 140 
Tom’s notes: This is a particularly interesting measurement for several reasons. First, it is now about ten weeks past the summer solstice, or the equivalent of mid-April in the solar cycle. Mid-April should be right in the middle of the spring sports season. Second, the ambient temperature was 79 degrees, which is not extreme for a nice spring day. Third, this was more than an hour before solar noon (remember we're on Daylight Savings Time) and there were a fair number of clouds around, so it was certainly not worst-case conditions. And I still got 140 degrees. Or 61 degrees above ambient, which pretty much matches published reports from New York. 
Peer’s comments: Cutting Field gets a lot of use and seemed somewhat compacted when we walked it last month. Is it possible that the older, more heavily used fields have the tire crumb 'floating' to the top with use and the sand filtering to below the crumb? This would give the field a higher heat factor even in the pre-noon sun. Plus Cutting is wide open without any of the trees around the new Lincoln-Sudbury football field, for example, but it would have been interesting to have a reading of that field in the same time period. Another theory - as the poly 'grass' fibers break down and get smashed they provide less shade and allow the sun more access to the tire crumb below to heat. This would be a different mechanism than the 'floating crumb' theory but with the same effect and thermal impact. Third theory - the air movement above the turf is critical to the heat flow and if the air is still or heavy the heat from the surface isn't dissipated and hovers and lingers over the carpet building up rather than being whisked away from the field. I was finding this to be an issue and could be a confounder on your readings. You may want to characterize the breeze - direction, rate of flow, and the THI - in case this is happening as it would have a dramatic impact on the readings if true. If not, never mind.
I'm guessing that compaction, use, and shuffling of the infill materials has something to do with the heat factor. Plus some fields tend to have more tire crumb and less sand - some competitors are all rubber (or all sand). Cutting may just have more crumb rubber infill.
Tom’s Rejoinder: There is a definite difference between fields, but my data from the Lincoln-Sudbury fields doesn't support an "old is worse" hypothesis. The new field there is notably worse, from readings taken minutes apart on two separate days. Thermal engineering 101 says that air flow cools a hot surface, and my observations have been that when a gust of wind comes up the temp reading drops noticeably. Think of blowing on hot food to cool it - Mommies were the original thermal engineers! Yesterday the wind was calm, and that may well have contributed to the result. But the best one can do to document the wind is to go to the NOAA website and look at the observations from the nearest reporting site. A more revealing research on this phenomenon would entail instrumenting a bunch of fields with continuously recording and, preferably, remote- reading temperature, wind, humidity, and solar sensors.

Also as reported on August 15, 2007 by Tom:

Lincoln-Sudbury athletic fields. Temps in degrees F, taken at surface. 
Instrumentation: Fluke Model 87 Digital Voltmeter, 80TK Thermocouple 
Module, Type K Thermocouple. 
 
August 3, 2007, 2PM. Hazy Sun.

The makers of Field Turf say it only gives off slightly more heat than grass, and I doubt the environmental argument is going to work on cost-conscious administrators. But I like any argument that leads to football being played on the surface Walter Camp meant for it to be played on: grass.




How hot was it? 132 degrees in the park
By Oatrick Arden, Metro New York
August 3, 2006 http://ny.metro.us/metro/local/article/How_hot_was_it_132_degrees_in_the_park/3767.html
MANHATTAN — On the hottest day of the year, it was 99 degrees just before 2 p.m. yesterday at the corner of 112th Street and First Avenue. But on the synthetic turf soccer field across the street in Jefferson Park, it was a scorching 132 degrees.
These measurements were low-tech, taken with outdoor thermometers purchased that morning in an Upper East Side hardware store by parks watchdog Geoffrey Croft, president of NYC Park Advocates.
While community groups have been expressing alarm over the Parks Dept.’s increasing use of “plastic grass” as a cost-saving measure, Croft was primarily concerned yesterday with the fake turf’s use of rubber crumbs from recycled tires. “I was worried about the quality of the air and the excessive heat,” he said.
Last month, Metro reported a Rutgers University lab sampling of rubber pellets from a synthetic athletic field in Riverside Park showed levels of polycyclic aromatic hydrocarbons (PAHs) that would be considered hazardous by the state’s Department of Environmental Conservation. Though PAHs have been associated with lung cancer if inhaled, Dr. Patrick Kinney, a professor of environmental health sciences at Columbia University, had said, “I don’t know if they can get in the body through the [turf's] rubber.”
Croft wondered whether a hot fake-turf field gave off toxic fumes. “Not only can you smell it but you can see the heat rising up in waves,” he said.
A neighboring natural-turf baseball field was 108 degrees. “It’s dirt, not rubber,” Croft said. “The synthetic turf field is 24 degrees hotter.”
Synthetic turf has long been known to get hotter than natural grass. In the spring of 2002, after complaints from its football team, Brigham Young University found “the surface temperature of the synthetic turf was 37 degrees higher than asphalt.” The university’s Dr. Frank Williams and Gilbert Pulley reported the surface temperature of artificial turf climbed to as high as 200 degrees.

The New York City Study (2006). One of this country’s preeminent experts on “heat island” effect is Dr. Cynthia Rosenzweig of the NASA Goddard Institute for Space Studies in New York. Her seminal work (co-authored with William D. Solecki and others) on abatement of urban heat island effect by means of installing green roofs is contained in Green Roofs: Urban Heat Island – “Potential Impact of Green Roofs on the Urban Heat Island Effect,” which is available at http://ccrs.columbia.edu/cig/greenroofs/index.html.

In January 2007 Dr. Rosenzweig spoke on “Climate Change in Our Back Yard” at a lecture sponsored by the Green Decade Coalition of Newton, Massachusetts. Presently she is exploring the mitigation of the “heat island” effect by turning rooftops green. And “by turning rooftops green,” she does not mean to cover them in artificial turf.

Dr. Stuart Gaffin of the Earth Institute at Columbia University is the lead-researcher on urban “heat island” effect in relation to synthetic turf. In the summer 2006 the Institute conducted urban heat island (UHI) reconnaissance around Manhattan and the Bronx. The study sampled many different urban surfaces, including sports turf surfaces in playgrounds and fields. The extremely high surface temperatures that were recorded on the sports turf were striking. Indeed, it appeared that such surfaces were among the hottest possible for urban areas, rivaling dark roofs and fresh asphalt. Typical early afternoon surface temperatures during the summer were in the 140 – 160 degrees Fahrenheit range.

In December 2006, Drs. Rosenzweig and Gaffin conveyed to mayor Bloomberg’s administration its concerns about the potential proliferating use of “sports-turf” and called urged that the sports turf manufacturers should be given a free pass to continue to manufacture their product without regard to urban heat island effect and urban combined sewage overflow water pollution.

In the letter to Mayor Bloomberg’s Long-Range Sustainability Planning Office, Dr, Gaffin and Dr. Rosenzweig identified four physical reasons for such high temperatures on the turf:

The University of Missouri Study (2005). On a summer afternoon in the year 2003, when the air temperature was 98° F, the surface temperature at the University of Missouri’s Faurot Field (FieldTurf brand) measured 173° F. The nearby natural grass showed a temperature of 105 degrees. The temperature at head-level height over the faux turf registered 138° F. The researcher who conducted the measurements stated, "If they are going to have artificial fields, we need coaches, parents and players to know that temperatures on these fields are going to be anywhere from 150 to 170 degrees on some days." Go here for details: http://www.plantmanagementnetwork.org/pub/ats/news/2005/synthetic 

The Utah Study. The results of the Earth Institute Study (New York Study) mirrored the results of the study conduct in 2002 at the Brigham Young University in Utah. In this study, at one point (2 PM on June 24, 2002), the surface temperature of the artificial turf surface measured 180° F, while the air at five feet above the ground measured 100° F. By contrast, the natural turf surface measured 93.5° F, while the air five feet above measured 96° F. What this data suggested was that natural turf was cooler than synthetic turf and the air five feet above the synthetic turf surface was considerably hotter than the natural turf superjacent air.

The following is Synthetic Surface Heat Studies by Drs. C. Frank Williams and Gilbert E. Pulley of Brigham Young University (2202):

Synthetic turf surfaces have long been regarded as a lower maintenance alternative to natural turf. However, synthetic surfaces like natural turf have their shortcomings. In the spring of 2002 a Field Turf synthetic surface was installed on one half of Brigham Young University’s Football Practice Field. The other half of the installation is a sand-based natural turf field. Shortly after the Field Turf was installed football camps were started. The coaches noticed the surface of the synthetic turf was very hot. One of the coaches got blisters on the bottom of his feet through his tennis shoes. An investigation was launched to determine the range of the temperatures, the effect water for cooling of the surfaces, and how the temperatures compared to other surfaces.

On June of 2002 preliminary temperatures were taken at five feet and six inches above the surface and at the surface with an infrared thermometer of the synthetic turf, natural turf, bare soil, asphalt and concrete. A soil thermometer was used to measure the temperature at two inches below the surface of the synthetic turf. Also, water was used to cool the surface of the natural and artificial turf. It was determined that the natural turf did not heat up very quickly after the irrigation so only the artificial turf was tracked at five and twenty minutes after wetting. The results of the preliminary study are shocking. The surface temperature of the synthetic turf was 37º F higher than asphalt and 86.5º F hotter than natural turf. Two inches below the synthetic turf surface was 28.5º F hotter than natural turf at the surface. Irrigation of the synthetic turf had a significant result cooling the surface from 174º F to 85º F but after five minutes the temperature rebounded to 120º F. The temperature rebuilt to 164º F after only twenty minutes. These preliminary findings led to a more comprehensive look at the factors involved in heating of the artificial turf.

Three aspects of light were measured along with relative humidity. The synthetic surface was treated as two areas, the soccer field and the football field and the natural turf was one area. Four randomly selected sampling spots were marked with a measuring tape from reference points on the fields so it could be accessed for subsequent data collection. Bare soil, concrete, and asphalt sampling areas were selected and marked in a similar manner. The results are shown in table form below:
 
Table 1.
Surface             Average Surface Temperature between 7:00 AM and 7:00 PM
Soccer                 117.38º F                 high 157º F
Football              117.04º F                 high 156º F
Natural Turf         78.19º F                 high 88.5º F
Concrete               94.08º F
Asphalt               109.62º F
Bare Soil               98.23º F
 
Table 2.
Two inch depth   Average Soil Temperature between 7:00 AM and 7:00 PM
Soccer                    95.33º F                 high 116º F
Football                 96.48º F                 high 116.75º F
Natural Turf          80.42º F                 high 90.75º F
Bare Soil                90.08º F
 
Table 3.
Shade                  Average Temperature between 9:00 AM and 2:00 PM
 
Surface Temperature of Natural Turf             66.35º F           high 75º F
Surface Temperature of Artificial Turf           75.89º F           high 99º F
Average Air Temperature                               81.42º F
 
Surface Temperature of A.T. (Artificial Turf) is significantly higher than air or soil temperature of A.T. The amount of light (electromagnetic radiation) has a greater impact on temperature of A.T. than air temperature. The hottest surface temperature recorded was 200º F on a 98º F day. Even in October the surface temperature reached 112.4º F. This is 32.4º F higher than the air temperature. White lines and shaded areas are less affected because of reflection and intensity of light. Natural grass areas have the lowest surface and subsurface temperatures than other surfaces measured. Cooling with water could be a good strategy but the volume of water needed to dissipate the heat is greatly lessened by poor engineering (infiltration and percolation).

Average air temperature over natural turf in the late afternoon is lower than other surfaces. Soil temperature of A.T. is greater than bare soil and natural turf. Humidity appears to be inversely related to surface and soil temperature. It is likely that energy is absorbed from the sunlight by the water vapor.
The heating characteristics of the A.T. make cooling during events a priority. The Safety Office at B.Y.U. set 120º F as the maximum temperature that the surface could reach. When temperature reaches 122º F it takes less than 10 minutes to cause injury to skin. At this temperature the surface had to be cooled before play was allowed to continue on the surface. The surface is monitored constantly and watered when temperatures reach the maximum. The heat control adds many maintenance dollars to the maintenance budget.

A budget comparison was made using actual dollars spent and for every dollar spent on the A.T. maintenance one dollar and thirty cents was spent on the natural turf (N.T.) practice field. While construction costs are very unbalanced, for every dollar spent on the N.T. eleven dollars and seventy-seven dollars were spent on the A.T.

The area under the carpet of BYU’s installation is designed to move water from the surface and into an extensive drain mat system. This part of the installation is two thirds of the overall cost of the A.T. Thus, for a 2.5 million dollars installation approximately 1.7 million dollars go for the subsurface and drainage. The most interesting thing about this is that the drain mat probably sees little or nº water. The surface is hydrophobic and the undersurface is poorly engineered to favor water retention rather than drainage. That seems like a high price to pay for something that does not work!

Artificial turf surfaces have their place in the turf industry. They can work in environments where grass will not grow and are marginal. However, they are costly and not maintenance free. It is important to take all the factors in to consideration before making a large investment. Don’t take the manufacture’s word for the factors of concern i.e. don’t let the fox guard the hen house. The propaganda on BYU’s installation is charts with surface temperatures less than the air temperature and claims for drainage of 60 inches per hour. The question still remains is A.T. 11.47 times better than natural turf?

Source: http://new.turfgrasssod.org/pdfs/Surface_Comparison_Heat_Study__F.pdf. For the spreadsheet/chart showing the measurements recorded by Professor Frank Williams on June 24, 2002, go to http://new.turfgrasssod.org/pdfs/Recorded_Temperature_Comparisons_Chart.pdf 

Type of surface        max. daytime surface temp    max. nocturnal surface temp

Green growing turf                31°C [= 62°F]                                 24°C 
Dry bare soil                         39°C                                            26°C
Brown dormant turf                   52°C                                            27°C
Dry synthetic turf                   70°C [=158°F]                                29°C
 
Source: James  B. Beard and Robert L. Green, “The Role of Turfgrasses in Environmental Protection and their Benefits to Humans,” in Journal of Environmental Quality, vol. 23, no. 3 (May-June 1994), pp. 452-460, table 1. reprint of this article go to: http://new.turfgrasssod.org/pdfs/Role_of_Turfgrasses_in_Environmental_Protection.pdf. Dr. Beard was formerly with Department of Soil and Crop Sciences at Texas A & M and is presently at International Sports Turf Institute ay College Station, Texas. Dr. Green id with Department of Botany and Plant Sciences at the University of California, Riverside, CA.

The New York Study recognized that using natural grass fields might not be an option in many communities and playgrounds. However, the authors of the study feel that this did not mean the sports turf manufacturers should be given a "free pass" to continue to manufacture their product without regard to the concerns of the urban heat island and urban combined sewer overflow water pollution impacts. In the same way that urban rooftops and asphalt are being re-envisioned and re-engineered to reduce urban heat island and combined sewer overflow impacts (green roofs, pervious pavement, light surfaces), turf manufacturers should also be approached about possible re-designs that reduce temperature and runoff.

Of the 4 causes listed above, the first 3 suggest possible alternatives:

    1. Use lighter pigments that still enable good sports performance. There may even be ways to alter the "near infrared"
    albedo of the turf that does not affect its visible spectrum. Such work is being studied at the Lawrence Berkeley
    Laboratories Heat Island group in connection with rooftops.

    2. Explore less filamentous systems that reduce micro light trapping.

   3. Explore creating pervious versions of the turf that may enable both evapotranspiration and reduced runoff.
   This would probably have the biggest temperature reduction benefit.