Sun reflective window films are great to reduce solar heat gains and glare, namely in hot climates. They can block up to 75% or the solar heat in single-pane glass windows, and 30% of the visible light.
Residential heat control window films are – as their name suggest - mostly intended to reduce solar heat gain, in situations where air conditioning costs are high. They may not be really important in cold climates.
Window films & Windows energy efficiency
Window films can be excellent in existing buildings with low-performance windows, but they are unnecessary in new construction.
New energy-efficient windows incorporate low-e and spectrally-selective metallic films. Modern windows can be ordered with low-solar-gain glass, and they do not need retrofit films.
The pros and the cons
Plastic window films can provide hundreds of dollars in energy savings each year, in hot climates. Other advantages: films can also cut glare and reduce furniture fading and, in some cases, winter heat loss…
But pay attention to their quality and their possible side-effects: some of them reflect indoor light at night, and block out views. Take into account their appearance.
Best types of reflective and non-Reflective window films
Windows films are not all created equal. Just be aware with the type of window film.
Tinted films (to simply color the window glass) are inexpensive but ineffective at blocking solar heat.
The best solar control window films are low-e spectrally-selective and provide a virtually invisible appearance. They are the best for energy savings, and can control up to 75% of visible light transmission. Since they are virtually invisible, they can be a great aesthetic option.
Low-e non-spectrally-selective films are less expensive. They too can be a good choice for energy-conservation, but are less effective than the spectrally-selective films.
Reflective silver window films – with a reflective appearance – are another good choice for solar heat gains control, but they are not “neutral”. Some manufacturers are also offering dual-reflective windows films, intended to be reflective on the outside and low-reflection on the inside.
Reflective silver window films provide solar heat control and day time privacy (but not nighttime privacy)
Reflective silver window films provide not only solar control but also privacy (during the day). They are very effective at controlling solar heat and glare (manufacturers claim that they stop over 99% of the UV rays).
These films are also designed as privacy window films; they provide a one way mirror effect during the day: they allow people to see out, but not in.
These films work by reflecting the brighter side, and they are useful in places and occasions where the sunlight is brighter than the artificial light. They do not work correctly at night time (or on internal partitioning situations). The outside (the side that you may want to be able to see through) has to be at least 4 times brighter than the room where you want privacy.
Insulating window films
There are windows films designed to reduce heat loss during the heating season, in cold climates, but these films are ineffective when applied over the glass.
Only window insulated films (applied to the indoor window frame) can be really effective at preventing heat loss. See: Insulating window films, cold climates
Residential decorative window films
Most decorative window films are just that: purely decorative. They do not provide solar heat control. They are inexpensive and have some sort of aesthetic value, or provide some sort of privacy, but they are not intended for energy savings.
Most homeowner complaints about window films involve their installation. Even films designed for DIY installation are not easy to apply. Installation
Some manufacturers require their films to be installed by certified installers, while others are promoting DIY installation. The installation is moderately difficult, and requires an absolutely clean glass surface.
Professional installation can be an important factor for success and performance, but contractors may charge you more than the cost of the film.
Most solar control window films are applied to the inside of windows but some more specific products (designed for glare control, or for privacy control are outside only)..
Some window film manufacturers recommend applying the film to cool glass; films should not be applied when the outside temperature is below freezing (or above 10-12ºF in the case of dual pane glass), or when the glass is being hit by direct sunlight.
Window films can be safely installed in dual pane windows if that is done correctly.
Residential window film manufacturers
There are several manufacturers selling window films for residential use.
In Europe see: European wind film association
When selecting a film, consider the brand… but do not forget other key factors: the warranty, the exact type of film or the film’s certification (NFRC, in North America).
These elements can be more revealing – and ultimately more important – than the brand.
NFRC certification label
In the US and Canada look for window films with the NFRC (National Fenestration Rating Council) label/logo. NFRC provides independent verification of window film performance. Window films can be very different in their scope and specifications, and the NFRC label can provide an accurate comparison of their performance.
Home Improvement Stores & window Films reviews
Window films can be found at home improvement stores such as Lowe’s, Home Depot or at Amazon.com. The sites of these retailers are also a way of getting access to customer reviews, namely the Amazon site. Some films have hundreds of customer reviews, which can be helpful.
Window Films Warranties
Vista films (a leading manufacturer of high quality solar heat control films) offers a lifetime manufacturer’s warranty. But that’s uncommon. Most window films endure for a few years, and most manufacturers have 5 year warranties, or less.
Prices vary a lot. They depend on the quality of the film, but also on many other factors.
Expect online prices around $40-$50 for 38/48 inches by 15 feet (see Amazon.com for reviews: Window films) rolls, and a lot more at specialty stores, namely when involving professional installation.