Absorptive Window Films
On reflection…
All film types reflect and absorb solar energy to some extent, but absorptive films are more absorptive than reflective.
As the name suggests, an absorptive film works by absorbing solar energy. It’s a film more commonly seen on cars where the airflow over a moving vehicle helps to keep the glass cool. Appearance-wise, as it has low reflection, it generally offers little in the way of privacy other than being a dark tint. On the plus side, you don’t have the internal reflection at night and it has a nice grey look. Think about limousine film, it’s an absorptive film with 5% VLT. As the film is blocking out 95% of light from the back windows, it’s going to be darker inside the car. The person in the back of the car can see out because it's lighter outside and you can’t see because of the reflective qualities of the glass and the film and it’s darker inside the car. If you want to see in, you cup your hands round your eyes and press your nose against the window again! You may then get to see the one way mirror in the police interview room!!
Depending on the level of tint of the absorptive film, it will absorb a certain amount of heat. As the glass isn’t cooled by air flow like a car, the glass gets hot when the sun is on it and, when the sun goes in, the glass starts to cool down again. I’ve recorded glass temperatures of 67oc in full sun and, in cases where there is a lot of glass and a small room, the heat radiated from the glass can make the room hotter rather than cooler.
Absorptive films are a good choice where the heat build up isn’t going to be an issue and where a low reflection is important. Compare the ratio of solar energy absorbed to reflected, as the greater the reflective qualities, the more it will help with daytime privacy and heat rejection.