With the ongoing intense heat, car interior temperatures can soar. Many car owners opt to install curtains or apply heat insulation film (also known as window tint) to reduce cabin temperature. What are the pros and cons of each option? And how should you choose legal and effective heat insulation film given Hong Kong's strict regulations on window transparency? Kwiksure shares the key things to bear in mind when selecting automotive heat insulation film.

Automotive Heat Insulation Film vs. Curtains

Both automotive heat insulation films and curtains are popular options for cooling down a vehicle. Here's a comparison of their benefits and drawbacks:

Automotive Heat Insulation Film Transparency Requirements

According to Hong Kong’s Road Traffic Ordinance (Cap. 374) and the Transport Department’s regulations, vehicle windows must meet specific transparency requirements. As of April 2023, the latest regulations are as follows:

• All windows (including the windshield) must have a transparency of 70%, unless otherwise specified.
• For vehicles with mirrors on both sides, the rear side windows of private cars, trucks, special-purpose vehicles, and buses must have a transparency of 44%.
• Upper-deck windows and windshields of double-decker buses must also have a transparency of 44%.

Construction of Automotive Heat Insulation Film

What exactly is automotive heat insulation film, and how does it keep the heat out? Automotive heat insulation films (Heat Reduction Window Films) are made from multiple layers of materials, including PET (polyester film), metal reflective coatings, organic dye coatings, scratch-resistant layers, and adhesive coatings. These layers work together to block, reflect, or absorb solar heat, infrared rays, UV rays, and glare, thereby reducing the cabin temperature of the vehicle.

How to Choose Automotive Heat Insulation Film

While the functions of heat insulation films are generally similar, they come with various specifications such as transparency, heat rejection rate, and glare reduction. Besides noting these values, you should also check if the film contains metal layers, as metal layers can block electronic signals, affecting devices like HKeToll, mobile phones, or in-car navigation systems. Always consult with the shop before installation.

Cost of Heat Insulation Film

Various brands offer different heat insulation films, and prices vary based on materials and installation methods. Here are the approximate costs for different brands (for a four-door car, in Hong Kong dollars):

Maintenance of Heat Insulation Film

Since heat insulation film doesn’t adhere perfectly to the glass edges, frequent cleaning may let moisture and air into the film, causing bubbles and reducing effectiveness. Clean with water and a towel gently. Also, if planning to steam-clean the interior, inform the service provider about the installed film to avoid damage.

Transport Department Exemption Application Procedure

After applying heat insulation film, you must apply for an exemption from the Transport Department to ensure compliance. Without this exemption, even if the glass meets transparency requirements, it may still be deemed non-compliant during vehicle inspection. The exemption involves the following steps:

1. Fill out the "Vehicle Exemption Application Form."
2. Submit the form along with a copy of the vehicle registration document to the Transport Department Vehicle Type Approval Unit, 1/F, Comprehensive Vehicle Inspection Building, 18 Sai Tso Wan Road, Tsing Yi, New Territories.
3. The Transport Department will send a reply letter in about 2-3 weeks.
4. Call to schedule an appointment to bring the vehicle to the inspection center for an inspection (no inspection fee required).
5. After passing the inspection, you will receive the exemption. Keep it in the car for proof during checks.

Source: Transport Department