Does Rubber Mulch Get Hot? What to Know and How to Cool It
Almost Anything Gets Hot in Direct Sun
Yes, rubber mulch can get hot in direct sun. On a bright day, a dark rubber surface can get hot enough to be uncomfortable or to burn bare skin. Many sun-exposed outdoor surfaces do the same. Shade and lighter colors help most.
How hot does it get?
There is no published standard figure for loose-fill rubber mulch, and we have not seen a head-to-head test against other surfaces, so we will not give a single number. The closest published test of loose rubber is from Penn State's Center for Sports Surface Research. It measured rubber granules used as turf infill after one hour under a heat lamp and found black rubber at 156.0 degrees F, tan at 153.4 and green at 147.9. That was a lab test of infill, not mulch in a bed or playground, so treat it as a sign of how rubber granules respond to sun, not a reading for your yard.
Why does it get hot?
Dark materials absorb more of the sun's energy. In the Penn State lab test, black rubber was about 8 degrees hotter than green rubber (calculated from 156.0 and 147.9 degrees F). The CPSC also singles out dark-colored plastics and rubbers, especially the surfacing under and around playground equipment, as materials that can get hot enough to burn.
What keeps it cooler?
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Lighter colors. Our pros and cons guide notes that lighter colors and shaded areas are less affected by heat. See our guide to rubber mulch colors.
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Shade. Rubber warms mainly from direct sun, so shade from a tree, awning or structure over the area reduces it.
Is it safe for kids and bare feet?
Check any surfacing before letting children play. The CPSC says that surfacing, including dark rubbers, can become hot enough to burn a child's skin, that the weather does not have to be hot for this to happen (it cites a burn on a 74 degree day from a plastic slide), and that some materials do not feel hot to a quick touch. Let's repeat this simple rule: check the surfacing before children play, and if it feels hot to your hand, it may be too hot for a child's bare skin.
Does wood mulch get hot too?
Wood mulch also warms in direct sun. Colorado State Extension notes that sun-exposed wood mulch can be hotter at the surface than gravel. Wood mulch does insulate soil better than rubber, which is one reason to weigh the two. Our rubber mulch vs. wood mulch comparison covers the rest.
FAQs
Does rubber mulch get hot in the sun?
Yes. In direct sun, rubber mulch can get hot enough to be uncomfortable or to burn bare skin, especially in dark colors. Shade and lighter colors reduce it.
How hot does rubber mulch get?
There is no single published number for loose-fill rubber mulch. In a lab test, Penn State measured rubber granules used as turf infill at 148 to 156 degrees F after one hour under a heat lamp. Real-world results depend on color, sun, air temperature and shade.
Does black rubber mulch get hotter than other colors?
Generally yes. Dark materials absorb more solar energy. In Penn State's lab test, black rubber was about 8 degrees F hotter than green rubber. The CPSC also lists dark-colored rubbers as a burn concern.
Is it safe for children to walk on rubber mulch barefoot?
It depends on the temperature of the surface. The CPSC advises checking the surfacing with your hand before children play and notes that if it feels hot to you, it may be too hot for a child's bare skin.
Does shade help?
Yes. Rubber heats mainly from direct sun, so shade over the area reduces it, and lighter colors are less affected.
Does rubber mulch get hotter than wood mulch?
Both warm in direct sun. We have not seen a head-to-head measurement of the two, so we do not claim one is cooler. Wood mulch insulates the soil better than rubber.
Can the heat hurt plants?
It can. University extension sources report that rubber mulch raises temperatures around plants more than organic mulch does. Choose lighter colors, use shade, and be careful around heat-sensitive plants in hot climates.
