How Much Water Is Needed to Cool Down Artificial Turf? Ways to Cool Synthetic Grass
One of the key advantages of artificial turf is that it requires very little maintenance. However, this is not to say that it doesn’t need any. In fact, in order to get the best use out of your artificial turf installation, you are going to have to regularly water it.
There are many reasons as to why you need to water, not least in terms of keeping the surface clean, but one of the main reasons why you will probably need to water your artificial turf is heat. If synthetic grass has one major drawback it is that it retains heat in its fibers, causing the surface to act in a similar fashion to a radiator.
Water is one of the most effective ways to cool down artificial turf. How much water is needed though, can be dependent on several different factors. Climatic conditions are the most obvious but factors such as the type, make and even color of the synthetic grass, as well as the variety of infill used, have a considerable bearing.
Why Does Artificial Turf Get so Hot?
When comparing natural grass, while artificial turf has some advantages over real grass, one of the properties that is yet to be replicated in synthetic grass is the ability of real grass to dissipate heat quickly.
The synthetic fibers that make up artificial grass absorb heat from the sun the heat. The heat not only stays in the fiber but it radiates it back heating the air temperature above and around the surface. So, not only does the grass become incredibly hot to touch with temperatures reaching up to 175° F[1] but the air above and around the artificial turf becomes hotter than the general air temperature.
Whilst real grass itself will still become hot, the surface temperature would generally only reach around 80-90° F, although in exceptional conditions it could rise to 100° F . This is because the heat will dissipate and will not store or radiate heat back into the air.
The reason that natural grass blades don’t retain heat is down to their structural composition. Real grass blades are cellulose material that is over 80% water. As the blade is heated water vapor is released stabilizing the temperature.
Thus, because of its structural composition, the overall surface temperature of natural grass rapidly cools. As it doesn’t retain or radiate the heat in the same way that synthetic grass does, it allows air temperature to remain the same.
How much of a problem this might be will, of course, be dictated by the climatic conditions. If you live in a more temperate climate then this is only going to be an issue in the summer months or on unseasonably hot days. On the other hand, if you live in more southern states, this is likely to be something that you need to consider for much of the year.
Properties of Artificial Turf that Contribute to Heat Retention
- Type of Artificial Grass
- Pigment Color
- Infill
Not all synthetic grass fiber is equal. Different fibers have different performances in terms of heat retention. There are specific products out there, constructed using space-age fibers, that are designed and manufactured so that the artificial turf retains less heat.
In addition to the synthetic fiber material, the actual color pigment of the grass and infill can have a considerable effect on how hot the surface temperature of artificial grass can get. A study conducted by Michigan State University found that the color of both the grass and infill used can affect the surface temperature by up to 8°F and using a special reflective pigment by a further 3°F.
If you choose the correct color reflective pigments and the right synthetic surface you can lower the surface temperature of an artificial lawn by around 15%.[2] This might not seem a great amount but it is significant, especially in terms of the amount of watering that will be required to reduce surface temperatures to those of natural grass.
How much water is likely to be needed to cool down artificial turf
Assuming that you want to bring the temperature down to similar levels as to those that would be present in real grass then the actual amount of water that will be required would depend on the surface temperature that the artificial grass is currently at.
This was proved by a test conducted by the New Mexico State University.[3] The research established that the quantity of water required for cooling artificial turf to similar temperatures to that of natural grass could be calculated reasonably accurately. They found that there is a direct relationship between the surface temperature of the artificial turf and the amount of water needed.
The ‘heat/balance’ formula arrived at is complex but in terms of the actual amounts of water used the table below should provide a guide to the water usage required to cool artificial turf:
| Surface Temperature at Start | Quantity of Water at 23oc | Surface Temperature After |
|---|---|---|
| 50°C / 125°F | 5.2mm / 0.21″ | 25°C / 77°F |
| 50°C / 125°F | 4.2mm / 0.17″ | 30°C / 85°F |
| 50°C / 125°F | 3.1mm / 0.12″ | 35°C / 95°F |
How Long Will the Watering Keep the Artificial Turf Cool?
The other aspect of the test evaluated the time that the cooling effect lasted after water was administered to the ground. The results showed that, when looking to bring the temperature down to values comparable to those of natural turf, the cooling effect water had on artificial grass only lasted for about fifty minutes. This explains why during sporting events artificial grass is often watered during a halftime break.
Of course, the other variable is the time of day. How long the watering effect will allow the grass to remain cool can be extended by watering at the right time of day. If you are looking to cool your grass in the late afternoon or early evening, then there will be less direct sunlight to reheat the grass, meaning that the cooling effect should last.
Comparative Water Consumption vs Natural Grass to Keep Cool
Obviously, you need to water natural grass to ensure that grows and continues to thrive. The amount of water here of course will also depend on climate. Clearly, you do not need to water synthetic grass to grow but there are a number of other reasons why you need to water artificial turf.
Here we are looking at the question of how much water is needed to keep artificial turf cool. So we will confine this discussion to this area.
Although as we have already mentioned natural grass has inbuilt cooling properties it is sometimes watered to reduce its surface temperature, especially in terms of sporting events. In terms of water consumption, the amount required is substantially less than would be needed for artificial turf.
This is because you are starting from a much lower temperature than you would with artificial grass. Because of this, you would probably only need to cool it by 10-15°F. In addition, the frequency required is much reduced, as the cooling effect lasts considerably longer because of grass’s natural cooling properties.
Ways in which you can reduce surface temperature
In addition to watering, there are other ways in which you can help reduce the surface temperature of artificial turf. We have seen that the choice of synthetic fiber and pigment color has an effect on surface heat as does the choice of infill. In addition, there are liquid cooling systems that can be used to bring down the heat
Using a Cooling Turf Infill
Because it increases the turf’s density, infill may also aid in the turf’s ability to retain heat. When it comes to choosing infill for grass in hot temperatures, there are a number of factors to consider:
Probably the infill that does the most to retain heat is crumb rubber. Although it is often used as a filler for athletic fields and play areas, it has a high capacity for heat absorption and is unable to release it. For this reason, among a few others, it is an infill that should be avoided.
In general, silica grass infills maintain a cool temperature, which is particularly important in hot regions; nevertheless, the cost of this kind of infill may grow rather high as it needs to be replaced regularly.
Other than silica, there are many different kinds of infills that have been developed in order to reduce the temperature of synthetic grass in hot climates. Some infills include moisture storage that is released as the artificial turf heats up.
When deciding on an infill, choosing a cooling infill is often advised for use in grass that will be exposed to hot weather and direct sunshine to help keep the artificial turf temperature down.
Liquid Cooling System
In a similar fashion to undersoil heating for turf, you can install liquid cooling systems for artificial turf.
Storing or running water beneath the artificial turf can draw out some of the heat from the surface through heat transference. This is obviously not a cheap solution but one you might consider if you are planning an artificial lawn and can afford it.
Summary: How Much Water Is Needed to Cool Down Artificial Turf?
Artificial grass has a few advantages but its propensity to heat up and retain this heat is a major drawback. There are several ways that you can help mitigate this problem, not least through the choice of synthetic fiber, pigment color properties, and using a cooling infill.
Natural solutions, such as providing shade and preventing direct sunlight, are also good ways to reduce the propensity of the artificial turf to heat up but these solutions are not always possible and unlikely to cover the whole area.
The most common solution is still watering. It is the most effective way to reduce the temperature of the artificial grass surface but requires time and water costs. The question of how much water is needed to cool down artificial turf is related to the surface temperature, but between 3.5 and 5.5mm of water will bring the temperature from 125°F to around 80°F.
In reality, it is probably a combination of the various methods that are going to bring the best results. If you can get the right type of artificial grass and infill you can reduce the starting surface temperature and therefore, the amount of water you need to use to cool.
Notes:
[1], [3]Kanaan, Ahmed & Serena, Matteo & Sevostianova, Elena & Sevostianov, Igor & Leinauer, Bernd. (2018). Quantifying Water Required to Cool Artificial Turf. 10.13140/RG.2.2.20797.10721. New Mexico State University
[2] TigerTurf: Serenity 30 and Serenity 40 TigerCool™