The location and orientation of heating and cooling vents are crucial for the safe and effective use of window film on flat glass surfaces. Vents directing air towards the glass can cause temperature variations, potentially leading to thermal stress. Heating vents can create hot spots by warming a cooler glass surface, while cooling vents can induce thermal shock by cooling a heated glass surface. These temperature changes, especially under the added stress from solar energy absorption and window film, can compromise the glass and film's integrity.

Positioning vents away from the glass helps maintain a consistent temperature across the window, reducing thermal stress risks and supporting the durability of the glass and film. Evaluating the heating and cooling system's layout, including air flow direction and vent proximity to windows, is vital. Adjusting vent direction or using diffusers to avoid direct air flow onto the glass can create a stable environment for window film application.

In essence, careful management of heating and cooling vent locations and orientations is key to minimizing thermal stress and maximizing the window film's benefits without risking the window's structural integrity.