There was no significant pattern or gain change for the antenna. The second type of film is the metal film sun screen. Results here were dramatic. The pattern was severely disrupted. The metallic film acts like a reflector to the signal.
Attenuation is a strong factor concerning propagation.
Some plastic films appear metallic, but may not be. There are three types of screen used as screening for windows. Plastic, fibre, and metal. The first two show some attenuation of the gain and pattern shape is similarly effected. Basically, the addition of the screen frame effects the VHF spectrum greater than the UHF spectrum.