It’s hard to beat the beauty and aesthetics of a glass-enclosed pool or waterpark. Natural light and the ability to see the outdoors makes for a more enjoyable aquatic experience for everyone.

But that experience comes at a price. According to the California Energy Commission, 30 percent of the cooling requirements of a glass-enclosed pool is caused by heat entering through the glass.

Stopping heat at the glass with solar-control glass or applied window film is the best solution. However, solar-control glass often exceeds the cost of standard glass to which a solar control film is later applied.

That’s why for new construction and all existing glass-enclosed facilities, applied window film typically is the least expensive and preferred option.

But not all window films are created equal. Conventional window films successfully block a significant amount of solar heat. What’s more, most of these films have a mirrorlike appearance from the outside. In artificial light and at night, they also can appear mirrored inside.

The result is darkened pool interiors and a reduced ability to see into and out of the water. This can lead to higher utility costs, which defeats the major benefit of the film cost savings.

That’s where clear, spectrally selective window film comes in.

“Spectrally selective” refers to the ability of the film to select, or let in, desirable daylight while blocking out undesirable heat. It offers the best ratio of visible light transmission to heat rejection. (For a chart on how applying the different types of film can affect the window, click here.)

Here’s how the spectrally selective films compare with conventional ones:

• Clarity Spectrally selective film, which blocks the same amount of heat as many of the darkest films, ideally transmits 70 percent of the visible light and, in so doing, possesses a clear appearance. Conventional films transmit less than 34 percent of visible light, according to manufacturers’ own data.

• Versatility Conventional and spectrally selective films can be applied to single-pane and insulating fixed glass, windows and doors, as well as laminated glass. Always identify existing glass and follow the advice of a qualified film installer.

• Price The price of tinted and reflective window film ranges from $4 to $6 per installed square foot. Depending on the particulars of the installation and the geographical area, the best spectrally selective applied window film ranges in price from approximately $9 to $12 a square foot installed.

• Payback Less expensive conventional window films have a shorter payback. However, given the cost of extra energy used for lighting and air conditioning due to its inability to transmit sufficient light, the payback for conventional film and spectrally selective film becomes comparable. Given rising electricity rates (with no end in sight), the rate of payback for spectrally selective film is always improving — averaging less than four years.

Also, some cities have rebate programs. In Los Angeles, for example, the Department of Water and Power gives conventional films a rebate of 55 cents per square foot. A spectrally selective film receives an 85-cents-per-square-foot rebate. Only spectrally selective films with luminous efficiency constants over 1.0 receive the higher rebate.

• Guarantees The best applied films are guaranteed not to peel, discolor, blister, bubble or demetalize. Always look for a guarantee from the manufacturer in addition to any offered by the installer.