The five key measurements to consider when selecting a window film are visible light, visible light — transmitted, visible light — reflected interior, visible light — reflected exterior, and the Solar Heat Gain Coefficient (SHGC). Understanding all of film's solar optical properties will help designers, property owners, and homeowners be better informed regarding the product that will best meet an individual property's unique needs.
Total Solar Energy: all the energy in the solar spectrum that reaches us on the earth's surface. This includes UVA and B, Visible light, and Infrared energy up to roughly 2500nm. Heat often refers to the total solar energy.
- Transmitted: the amount of total solar energy that passes through the glass into the building.
- Reflected: the amount of total solar energy that is reflected off of the glass and directed back outside. This energy does not come into the building.
- Absorbed: the amount of total solar energy that is absorbed in the glass. This heats up the glass, making it hotter to the touch, and reradiates a small amount of heat back into the room. The majority of absorbed energy is kept out of the room though.
Visible Light: the portion of the solar spectrum containing visible light we can see, from roughly 370nm up to 770nm, contains all the colors of the spectrum.
- Transmitted: the amount of visible light that passes through the glass, into the building. This is how light or dark the film is.
- Reflected Interior: the amount of visible light that is reflected off the interior surface of the window. This is seen when standing inside the building looking out. A higher reflectance value means the window looks more like a mirror from the inside.
- Reflected Exterior: the amount of visible light that is reflected off the exterior surface of the window. This is seen when standing outside the building, a higher reflectance value means the window looks more like a mirror from the outside.
Ultraviolet Light Rejected: the amount of UV energy blocked by the film, either by reflecting or absorbing it. This energy does not enter the building.
Glare Reduction: the reduction in visible light transmitted compared to clear non filmed glass.
Infrared Rejection: the amount of infrared (IR) energy that is blocked by the film, either by reflecting or absorbing. This value is for the whole IR region of the solar spectrum, roughly 780nm up to 2500nm.
Total Solar Energy Rejected: the total amount of solar energy that is kept out of the building. This is commonly referred to as heat rejection.