Effect of Dyed Films -vs- Ceramic Solar Control Films on Vehicle Interior Temperature
Introduction
Solar control coatings or window films have been used extensively in the automotive industry to cut the glare and the heat out. The technologies used are vastly varied, from metalized to dyed to ceramics. However, the effectiveness of such films in keeping the car interior cool has not been widely tested and documented. In this report, the results of a car temperature experiment conducted using dyed and ceramic based films is discussed. The key objective is to simulate the heat filtering effect of installing a dyed and ceramic window film compared to a car with no film under stationary, parking condition.
Figure 1: Photo of the Car in the Climate Chamber
Methodology
A climate control chamber is used for this test. It consists of an enclosure big enough for a car and several halogen light sources. A car is parked in the chamber and several halogen light sources are used to provide the heat and light to simulate the solar energy from the sun. The car model used for this experiment is a Honda Jazz, a very popular car model worldwide. The light sources are directed towards the glazed area of the car, including the front and rear windshields, and the side windows as shown in Figure 1. The distance of the light sources and the power levels are shown in Table 1 below:
Table 1: Distance and Wattage of the Halogen Light Source
Temperature Logging
Temperature loggers are placed on the front and rear dashboard to record the rise in temperature when the light sources are turned on. This is to record the temperature at the front and the rear space of the car. The loggers record the temperature every minute. The entire logging time for each cycle is 120 minutes. This is to allow sufficient time for the car to attain thermal equilibrium, ie the maximum temperature attained in order to stress the films to the maximum extent of filtering out the solar heat.
Films Used for the Experiment
In this experiment, two series of films utilizing different technologies, ie dyed and ceramic are used for the testing. The dyed films used is Brand 3X. The ceramic films used are Hüper Optik’s C70 and C15. The specifications are shown in Table 2 below.
Table 2: Product Specifications of the Films Tested
The film combination for Brand 3X used for the test is such that the clear film and dyed film are used for the front windshield and the rest of the car respectively per the schedule in Table 3. For Huper Optik Ceramic films, C70 is applied on the front windscreen and C15 applied on the rest of car glass.
Table 3: Schedule of Film Combinations Used
Results
The maximum temperatures attained are given in Table 4, while Appendix 1 shows the temperature curves over time for the front and the rear of the car respectively.
Table 4: Maximum Temperatures Attained
Analysis
The results clearly show that the temperatures for the Hüper Optik film combination kept the car coolest when compared to no film applied and to dyed films.
Film Vs No Film
The Hüper Optik’s C70+C15 combination kept the front and rear of the car 12.7°C and 7.9°C cooler respectively than the car without any film. This is a very significant result as it shows that even after 120 minutes of exposure to the halogen light source, the Hüper Optik films still maintained a significantly lower temperature, about 22% and 15% cooler for the front and rear respectively compared to the control situation where no film was installed. While the 3X films also kept the car cooler than a car without film, the extent of the heat rejecting effect was less than the single-layer Hüper Optik films. 3X films only resulted in a temperature drop of 7.8°C and 2.8°C for the front and rear of the car respectively. This infers that in an actual situation where a car is parked under the sun for a long time, it is important to install films that can keep the car interior cool so that the driver will not feel major thermal discomfort when he enters the car. The air-conditioning also takes a shorter time to cool down when it is switched on after a prolonged period of exposure to the sun.
Dyed Films Vs Ceramic Films
The type of film used is also a key factor in keeping the car cool. By comparing the temperature difference between the 3X and Hüper Optik test results, it can be seen that 3X’s maximum temperature attained was significantly hotter than a ceramic based film like Hüper Optik for both the front and rear of the car. The clear ceramic film, C70 for the front windshield can result in a cooler cabin temperature for the driver in the front by about 4.9°C compared to the Clear 3X film tested. This is also evident from the specifications of both films, where the Total Solar Energy Rejection of the C70 is 13% higher than the Clear 3X. For the side and rear windscreens, which use dark films, the key criteria is to combine glare and heat protection. The film must be able to cut down enough visible light and infrared radiation. The C15 kept the car cooler by 5.1°C cooler than Rear 3X film, indicating that the 3X, which is a dyed film, was only effective in filtering visible light but not infrared radiation. In fact, putting 3X for the sides and rear windshield could only cool the car marginally by 2.8°C compared to if the car had no film at all.
Figure 2: Temperature Loggers (white) on the Front and Rear Dashboard
Conclusion
A temperature study conducted on a Honda Jazz showed that installing a Ceramic based film such as Hüper Optik on the car can reduce the interior temperatures by approximately 7.9°C to 12.7°C versus a car without any film. A similar comparison between the same Hüper Optik ceramic films and 3X dyed films also showed that the ceramic films outperformed 3X dyed films by as much as 5.1oC. The findings are significant as it provides an insight on how the selection of the right type of film can improve the thermal comfort level of the car significantly. The human skin is extremely sensitive to temperature changes, even to the extent of detecting variations up to 0.1°C to 0.3°C. Thus the positive effect of installing window films for cars cannot be underestimated, especially where high performance films such as Hüper Optik can be used to reduce the interior temperatures by up to 12.7°C.
Disclaimer: The above study is based on the test results conducted by EurekaLab. It does not constitute a recommendation, endorsement, certification or warranty for the product tested. Actual performance of the product may vary under different operating conditions. EurekaLAB Test Report NVXTD2009-007
Tags: ceramic window film, Huper Optik Window Film, window tinting
Window Tinting blocks the UV rays, heat reduction, etc with unsurpassed durability; Not only to protect the skin but also to Protect the interiors and also the Residence. Excellent post! keep posting!!
Why are the starting temperatures (time 0) different for all three experiments? If you factor that in, the difference in the surface temperature between those with film and without film is negligible.
Good question Vincent. We are logging ambient temperature and not surface temperature. In paragraph 3 it says “The loggers record the temperature every minute.” The data loggers are temperature and time recording devices that take a reading every 60 seconds. So your first temperature reading does not actually take place at “0 minutes.” So start temperatures are not going to be identical in each experiment because the interior of the vehicle has already been exposed to the heat source for 60 seconds and thus the differences.
The important thing to take note is the temperate spread as time goes on. Referring back to the article notice that; “The entire logging time for each cycle is 120 minutes. This is to allow sufficient time for the car to attain thermal equilibrium, ie the maximum temperature attained in order to stress the films to the maximum extent of filtering out the solar heat.”
Thank you for your comment.
Thanks for the reply. Generally I can accept your explanation that the time 0 is just an arbitrary point in time. More importantly is the actual temperature reading when it reaches a plateau (equilibrium) after some time.
You mentioned that you are measuring the ambient temperature but I could not quite agree on this. To measure ambient temperature, the probe should not see the heat lamps directly and away from a heat absorption surface such as the dash board.
In a real world, a car parked under the hot sun gets a lot of conducted heat into the interior from the metal roof/surfaces/windows in addition to radiant heat from the windows. Therefore, I wonder if a solar film (any type) actually helps in reducing the ambient air temperature in a stationary car much. Nevertheless I am a full believer of the benefit of solar film for a car on the move during a sunny day.
I was hoping someone could conduct a simple experiment and put to rest the “burning” question whether solar film can make the ambient temperature of a stationary car under the sun cooler. I suppose the experiment would just need two identical cars. One with window film and another without. A protruding temperature sensors in the middle of the car, sheltered from direct sun light would then measure the interior AIR temperature after achieving equilibrium, say after 2 hours.
That is the point of this experiment, namely the change in temperature over time. Eventually, all three test cases will reach equilibrium at varying rates of time similar to what happens in vehicles that are parked out in the sun all day.
Some disclosure is in order here. We did not conduct this test. Vision Quest Distributing is simply publishing the results on our blog of a test that was done by an independent lab. Personally, if it were me I would have suspended the data loggers in the air using something that is non-conductive. Setting them on the dash is kind of shooting themselves in the foot because you do get thermal bridging from the dash absorbing energy.
Even if you were to measure ambient temperature this way, what you will find is a warming trend at varying levels depending on the film’s ability to filter energy. It would be very similar to the graph we have just maybe the exact temps would differ slightly from the temps shown here but the spread from one test vehicle to the next would be very similar. A decrease in ambient temperature is really not possible. The reason being is that window film does not cool vehicles. Air conditioners are what cool or condition the air, the film just filters incoming energy from the sun that transmits through the glass and the glass only. Reduced solar transmission decreases the rate of heat gain and lowers the cooling demand thus the air conditioner will not have to work as hard to reach the desired set point.
There is another factor that is not taken into consideration in this experiment and that is reduced energy absorption. Incoming near infrared is absorbed by interiors and us and then is re-radiated as heat. Window films have the capability of filtering out near infrared so while we are driving we feel more comfortable behind a filmed window because the IR transmittance and resulting absorbance is greatly reduced. There is no substitute for real world park it out in the sun results, but in this case the lab becomes the equalizer between the control and test subjects and gives some numbers for those that ask. At the end of the day if you were to drive in a vehicle filmed with Huper Optik versus an unfilmed vehicle or even a vehicle with traditional window film, you would definitely be able to tell the difference.
Thanks again for the expeditious reply.
Just a minor clarification, when I mentioned cooler ambient temperature, I meant relative to a parked car without solar film.
Secondly, you went to some length trying to explain the benefit of the solar film while driving. Allow me to admit…I am a total believer of this already as my 3 previous cars and present one all had solar film installed but I am just very skeptical about the benefit of the solar film (again I stress any type of solar film) in moderating the air temperature of a car parked under the hot sun for a long duration unless an actual real world test shows otherwise. I have yet to locate any such test results on the Internet hence I can only conclude that such a real world parked car test if exist is deemed not a positive promotion of their products hence not published. By the way I live in the tropics.
The reason you do not see “real-world” parked car data is not because there are no positive marketing benefits. Window film filters light, IR, and UV whether it is indoors or outdoors that is what film does. It will help delay the amount of time that it takes for a parked car’s interior to heat up as the graph shows. Depending on film construction, some films will excel at this much more efficiently than others.
So let’s say we were to set out to conduct an outdoor experiment. Could we duplicate all conditions? We would need 3 like model cars and we would have to test them all at the exact same time in the exact same orientation and in the exact same position to make all things “equal.” The first three criteria are doable but the last is impossible. So an outdoor experiment would be slightly skewed. Someone could take issue with that and probably would…
I understand your position but I really doubt it is marketing ploy as you suspect.
Thanks.
You mentioned “…it will help delay the amount of time it takes for a parked car’s interior to heat up…”
I can accept your explanation if the duration the car is parked under the sun is short. Sometimes we park our car for just a few minutes to run an errand. I suppose in such a situation where the duration is too short to achieve thermal “equilibrium”, the interior air temperature of the car would be cooler compared to one without the film installed.
It has been a pleasure having this technical discussion with you. It did help to further convinced me that the few thousand dollars spent installing solar film in all my cars was definitely worth it. Nevertheless, I will still keep searching in the Internet for the elusive test data of the car parked under the sun for an extended duration. (my car is usually parked at my work place from morning till later afternoon under the blazing tropical sun)