Heat from reflective surfaces can cause damage to hot tub covers and siding.

Hot Tub Hazards

Shedding light on the dangers of reflective surfaces

While issues like pad size, electrical standards and spa accessory requirements are typically addressed during hot tub installation, the potential damage caused by reflective surfaces — like greenhouses, clear-roofed pergolas and windows — often receives less attention from spa retailers.

According to James Kendell, director of sales and marketing at Bullfrog Spas of Northern Utah, low-energy, heat-reflective windows in particular have been known to cause warping and damage to nearby hot tub siding as well as vinyl and hardcovers. 

When a cover is damaged from the harmful reflection, the foam inside it melts, often in the shape of nearby windows, leading to distortion or bowing. 

Robbie Reenan, product manager of accessories and sourcing for Core Covers, adds that reflected heat from windows can raise the surface temperature to 175 degrees or higher.

“Though [hot tub cover] materials have great UV inhibitors to help with fading, it can melt the components,” he says. “The issue of heat damage is not limited to covers but includes cabinets as well. It is recommended to install hot tubs 20 feet away from windows.”

Rob Anderson, vice president of Olympic Hot Tub, shares one case when a customer had all their windows replaced with low-energy panes not long before buying their hot tub. 

“We got called because their Smartop [cover] was melting,” he says. “Sure enough, there was a hole melted in the center of one half of the Smartop. We discovered the customer’s second-story window casting a reflection on it. We measured [the temperature of the] reflection with an infrared thermometer, and it was 270 degrees.” 

For comparison, the shaded portion of the cover was the same temperature as the ambient air, while the portion in the sun but not in the reflection from the window was around 130 degrees. 

“The moment I received this information from our service technician, a light bulb went off, and I realized vinyl covers have been getting damaged this way for years, and we had no idea,” Anderson says. 

Anderson has seen glass patio lights refract the sun onto a hot tub cover, causing damage. He adds that there are often signs around the yard that the sun is causing the damage. It may be patio furniture with odd fading patterns or synthetic decking materials that show signs of warping. Or it could be the side of the hot tub or swim spa itself that’s warping and melting. There have even been news reports of car parts warping due to reflective sun damage.

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“I’ve found you often have to think outside the scope of the specific thing you’re looking at, including sometimes looking outside the customer’s yard, to find the real answer to why the same customer keeps having the same half of their cover pooling over and over,” Anderson says. 

While customers often notice the problems, they may not notice when it happens, which also adds to their disbelief. 

“The sun moves across the sky not only throughout the day but also changes position in the sky throughout the year, which means the angle of the sun also changes,” Anderson says. “While a customer may notice damage today and blame the for failing, the damage may have actually occurred days, weeks or months ago.”

Even though the most obvious solution would be to place the spa in a spot without harmful reflections, it isn’t always an option. In those cases, Kendell recommends installing a clear, matte-finish, UV film on the window or reflective surface, which can block up to 99% of UV rays and reduce damaging reflections while still allowing light into a home.

Anderson says customers should also avoid putting any type of clear plastic covering on or over the hot tub, including tarps and corrugated roofing materials. And don’t forget to look next door, Kendall says; damage could occur from a reflective surface in the neighbor’s backyard.

Spa retailers can help customers avoid heat damage by educating them on the issue at purchase or during a predelivery assessment. Manufacturers can help, too, by including warnings and precautions in their manuals and materials. 

“There are several things to consider when picking a location to set a spa: the distance from the home, the view, room for accessories to operate and a structurally sound flat surface,” Kendell says. “Potentially harmful reflective surfaces are also something spa retailers should include in their predelivery guides, site visits and checklists.”

Because as well-made as a hot tub cover can be, heat reflection can do real damage.

Customer Resource

Struggling to talk to your customers about the risks of reflective surfaces damaging their spas and covers? Check out our consumer-friendly article on Spasearch that you can easily share.