No matter how much car manufacturers improve the panoramic sunroof, it still gets hot under the sun.

While we're discussing how "well - done" the Indians will be in the 2026 "big roast", summer has also arrived here.

In recent days, we can gradually see some car owners starting to wear hats, sunglasses and the like in their cars.

The reason why everyone has become like "Kamen Riders" is, apart from the extremely hot weather, undoubtedly the panoramic sunroof that people have been complaining about for several years.

Riding on this 30°C weather, Brother Neck will have a clear talk with you about this thing today and also tell you how to do a good job in sun protection.

Nowadays, having a sunroof on top of a car is basically a habit brought by Tesla.

With a plain white interior and five - sided transparent glass, when it's not sunny, the view inside the car is actually really good.

But behind the sunroof, there are actually engineering problems: New - energy batteries take up the space in the chassis. If the car height is the same as that of a fuel - powered car, the fragile battery could be easily damaged and explode at any time.

So, unless using special - shaped batteries like the Porsche Taycan, most electric cars choose to raise the sitting position of passengers to make room for the batteries.

In order to ensure enough headroom, the original roof made of iron sheet and ceiling has to be replaced with a thin piece of glass, trying to save as much space as possible. (Unless it's made like a Beetle, shortening the L113 of the car and arching the middle of the roof)

However, the little headroom saved can't make up for the fact that this thing is really hot in the sun...

Research by the Korea Automobile Technology Institute shows that car windows already account for 50% - 75% of the heat entering the car (the windshield alone accounts for 40%).

If you add a panoramic sunroof of nearly two square meters, which is larger than the front windshield and has a good sunlight incidence angle, it's hard not to get hot.

Do you think car manufacturers don't know this? They definitely do. Otherwise, they wouldn't use various silver - plating technologies.

However, even silver - plated glass doesn't work as well as advertised.

Here, we need to say a word for car manufacturers. It's true that they claim a 99% UV isolation rate and over 90% infrared isolation rate.

Now some car owners put on ice sleeves and face masks as soon as they get in the car, and there are even some tough guys who hold umbrellas in the car. But in fact, there's really no need to wrap themselves up like people in the Middle East.

As for the UV isolation of car glass, as early as more than 100 years ago when laminated glass was invented, 90% of the problem was solved by the PVB (polyvinyl butyral) in the middle layer. Later, in the 1970s, chemical companies added UV blockers to PVB, and the UV isolation rate can reach over 99%.

So, if you're just afraid of getting tanned, there's really no need to dress like people in the Middle East.

In our mandatory national standards "Technical Conditions for Motor Vehicle Operation Safety" and "Safety Technical Specifications for Motor Vehicle Glass", it is also specified that the front windshield of a car should use laminated safety glass and plastic - glass composite materials.

The glass that doesn't break when smashed is laminated glass.

Now, even most compact cars priced between 150,000 and 200,000 yuan use double - layer laminated glass for each window to improve riding quietness, and there's no problem with UV protection.

As for infrared rays, their harm is not as serious as that of UV rays, which may cause skin cancer. It's just that the energy of infrared rays is greater than that of UV rays, and it's purely heat.

So, car manufacturers and chemical companies came up with another way. They referred to those shiny metal plates and used the high - reflection and high - transparency properties of silver atoms to create silver - plated glass to reflect infrared rays back.

Does it sound familiar? Yes, these are the window films that the 4S stores persuade you to apply when you buy a car.

However, car manufacturers not only moved these window films from the outside to the glass interlayer, but also used the top - grade ones, and their heat - insulation ability easily exceeds that of window films.

For the front windshield film, Xiaomi is much better than V - Kool, a leading brand in the industry.

But the problem is, as we learned in junior high school, sunlight not only contains UV and infrared rays, but also visible light, which accounts for 44% of the energy.

As the saying goes, visible light must be visible \😭/.

This nearly half of the heat is the reason why even if car manufacturers use various sun - shading methods, as long as the car is parked in the sun for half an hour, the inside of the car can still be as hot as a sauna.

If you don't want to absorb this part of the heat, you can only block it. As a result, the sunshade curtain is the optimal solution.

Research by BYD shows that after being exposed to the sun for a while, the average temperature inside the car with a sunshade curtain and ordinary glass is 39°C, while the average temperature of the control group with a silver - plated sunroof is 68°C.

So, now car manufacturers and glass companies are starting to develop EC dimmable sunroofs and PDLC liquid - crystal dimmable sunroofs, directly changing the color of the glass to block visible light.

But to be honest, it still can't compare with a normal sunshade curtain.

Not to mention the optional price of 10,000 - 20,000 yuan. The specific heat capacity of glass is larger than that of the iron sheet on the car body surface (the specific heat capacity of glass is 0.84J/(g·°C), and that of iron is 0.46 J/(g·°C)). This means that if both are fully exposed to the sun, the glass will cool down more slowly.

The hot air inside the car has a lower density and will naturally rise to the top, gathering above our heads. The sunroof keeps heating this air, while the cold air from the air - conditioner can only gather in the lower part.

So, when we get into a car that has been fully exposed to the sun, our heads have to endure a sauna - like environment for a while.

Here, Brother Neck also gives you a little life tip. If you forget to turn on the air - conditioner in advance, the most effective way to cool down is to open all the windows and direct the air - conditioner towards the objects inside the car that cool down quickly, such as the seats.

When the seats are no longer hot, drive the car and use air exchange to cool down the sunroof...

Of course, the most useful thing is to close the sunshade curtain when parking.

You can buy one on Taobao for a few hundred yuan, and it will solve your problem.

This article is from the WeChat official account "Chaping X.PIN". The author is Haosen, and the editors are Brother Neck Right - Twist and Mianxianhu Jun. It is published by 36Kr with authorization.