Yes, tinted car windows do reduce heat inside of the car

Every car owner knows a hot day can feel even worse when you climb into a car that’s been sitting outside. Interior car temperatures can reach well over 100 degrees after just an hour of sitting in the summer heat. 

People try all kinds of things to keep their cars a little cooler while they’re out in the sun, including adding extra tinting to their car’s windows. Dark windows may increase your privacy, but do they actually cool the interior too? That’s what VERIFY reader Em wanted to know. 

THE QUESTION

Do tinted car windows reduce heat inside of a car?

THE SOURCES

• AAA

• Kelley Blue Book

• University of Wisconsin-Madison College of Engineering

• Study presented at the International Conference on Mechanical, Automobile and Robotics Engineering in 2012

• Literature review by the Virginia Department of Motor Vehicles in 1994

• Report by the National Bureau of Standards from 1974

THE ANSWER

Tinted car windows do reduce heat inside of a car.

WHAT WE FOUND

AAA says window tinting can “keep the interior of your car a few degrees cooler” and Kelley Blue Book says tinted windows block heat at varying levels depending on the type and quality of the tint.

Cars in the sun get hot because sunlight passes through the windows and is absorbed by the interior surfaces of the car, which then radiate heat back into the air, a University of Wisconsin-Madison College of Engineering blog post explains. Heat has a harder time passing back out of a car window than sunlight does passing into the window, so the heat gets trapped in the car.

Tinted glass can help a car from getting as hot by reducing how much solar radiation enters the vehicle in the first place, the blog post says.

For decades, studies have found tinted windows can help reduce a car’s internal temperature by at least a few degrees. The studies have shown that you don’t have to tint all of your windows to see a decline in your car’s interior temperature.

Research presented to the 2012 International Conference on Mechanical, Automobile and Robotics Engineering found that tint film applied to all of a car’s windows including its windshield reduced the car’s peak internal temperature by 8 to 10 degrees Fahrenheit.

A literature review by the Virginia Department of Motor Vehicles from the 1990s studied different types of extra tinting. Researchers found that cars with tinting just on the rear window, cars with tinting on the rear window and back side windows and cars with tinting on all windows except the windshield were 2 to 4 degrees cooler than cars without any extra tinting at all.

And even as far back as 1974, National Bureau of Standards testing found that interior temperatures of a car with a tinted windshield were lower than the temperatures of a car without any tinting.

But before you darken your car windows, check your state’s laws. Some states restrict which windows you can tint, how dark you can tint your windows or which colors or materials you use for tinting. A few states allow the entire windshield to be tinted, but most states restrict windshield tinting to just the uppermost portion of the windshield. You can see each state’s window tinting laws in this chart provided by a window film company.