Some people tell me things like, "I just need tint" or "I need to block the sun." Please understand I need a bit more information in order to help you. I need to know the specifics of your goals and your windows. There will be questions I need to ask to understand all scenarios to recommend the correct product type. Below is a basic explanation of the different types of window films, and I will narrow down the selection based on the information you convey to me. All solar films reject >99% UV. Glare reduction and daytime privacy are determined by darkness, or visible light transmission. Nighttime privacy cannot be achieved with tinting of any kind due to the direction of light. Only a frost or decorative film of some kind will provide privacy at nighttime. These are not specific to any brand of window film.
These are the oldest types of window films. They're still fairly popular in commercial applications, but not so much in residential due to color and interior and exterior reflectivity. Their solar performance is excellent and have low solar absorption. Silver films have a bluish-gray tone and usually come in shades of 20%, 35%, and 50% visible light transmission. Bronze films have a bronze color and usually come in 20% and 35%. Bronze films used to come in 50% but most manufacturers have discontinued that level. These films cost the least and give a lot of bang-for-your-buck if thousands of square feet are needed.
Dual-reflective films have become the most popular for both residential and commercial applications. They're used when high solar heat rejection is needed as well as glare control. The interior side has very low reflectivity and the exterior side gains reflectivity with darker shades. There are two types of dual-reflective films: Fully metalized and metal/dye hybrid. The fully metalized version will have a bluish-gray tone while the hybrid has an earth tone. It's a matter of color preference and which one looks better against the window frames and decor. These films are still lower on the price spectrum and range from 5% to around 40% visible light transmission.
These films are extremely popular in residential applications for their neutral and colorless appearance. When solar heat gain or glare aren't too bad but your main concern is protecting furnishings from fading, neutral films are a good fit. If you have a lot of white walls, trim, and decor, neutral films are nice because they won't cast a different hue causing a change of color of daylight. Visible light transmissions range from extremely light (about 65%) down to medium shades (about 35%). There are darker versions out there but their solar absorption levels are high and should only be used if the window composition allows them. Neutral films are in the same general price range as dual-reflectives.
When high solar heat rejection is needed without sacrificing more visible light than necessary, spectrally-selective films are a good choice. These films got their name because the ratio of visible light transmission to solar heat rejection (luminous efficacy) is over 1. Most of these films are non-reflective and extremely light (60%-80% visible light transmission) with solar rejection numbers around 50%-65%. There are medium shades that are reflective and are huge performers in knocking down solar heat gain. Because these films concentrate on infrared (or IR) rejection, please don't fall for IR rejection numbers. These numbers only specify particular IR wavelengths and do not measure the entire IR spectrum like the 99% number for UV rejection. This is a sales tactic and is deceiving. When choosing a spectrally-selective film product, look for an IR reflector and not an IR absorber. Look at the specification called Solar Absorption. This number is explained below and should be lower than the low-40% range. If the manufacturer does not publish this number, you should ask why and assume its absorption may be too high for expected performance. Due to the way spectrally-selective films are made, they are the most expensive.
Ceramic films are King Almighty in the automotive world, but I do not recommend them for flat-glass applications. Their solar absorption is simply too high for dual-paned annealed glass and don't provide much more performance than a neutral film of the same visible light transmission. If anybody is trying to sell you ceramic for your home or commercial windows, ask to compare the solar performance to a neutral film of the same darkness. Yes, ceramic films are non-reflective, but they're not worth the higher cost.
Low-E (low emissivity) films provide not only high solar heat rejection, but also winter energy savings. They do this by reflecting the infrared energy (or heat) back into the room (see below for emissivity explanation). Most low-e film products are fairly reflective because of how they're made and are a bit higher in cost. The additional cost is usually well worth it if your windows don't have a low-e coating. If your windows already have a low-e coating, then using a low-e film is moot and will not give you anything additional during the winter season.
These films are used in areas where added safety from breaking glass is needed or to drastically slow down an intruder when a glass pane is smashed. There are many thicknesses and they come in either clear or solar tinted. Safety films are those with thicknesses up to 7 mils, and are used for basic safety such as when a golf ball hits a window to prevent glass shards from harming people and making a mess. Films from 8 mils and thicker are considered security films. These are used mainly on entry doors or large window panes to slow an intruder. Security films need to be attached to the frame in some manner so the glass can't just be pushed inward. The most popular attachment method is a bead of Dow Corning 995 structural adhesive. There are claims out there that security film makes glass bulletproof. This is not accurate!
Frost films are extremely popular in bathrooms and on doors. They come in a variety of colors, but white is hands-down the most popular. When privacy at nighttime is needed and the view outward is nothing to care about, a frost film is perfect. There are LOTS of decorative films out there if you're looking for some added pizzazz. Click below to check out all of the possibilities. If you see something you like, let's discuss the details, get it ordered and installed.
Visible Light Transmission (VLT): This is the amount of light we can see that passes through the film. It's the level of tinting and the lower the number, the darker the film.
Ultraviolet Rejection (UV): This is the amount of UV light that comes through your windows that is rejected with the film. All solar films reject >99% UV.
Infrared Rejection (IR): This is the amount of infrared light that we feel as heat that is rejected by the film. Unlike the UV rejection number, IR may only be measured within a certain wavelength of the IR spectrum. This should be noted and not to be confused with the entire IR spectrum.
Visible Light Reflectance (Interior & Exterior): This is the percentage of reflectivity. Plain glass has a reflectance of 8% and most windows with low-e coatings can be up to around 15%. Reflectance ratings up to around 25% show a moderate sheen. Ratings in the 30%-40% range are fairly shiny and ratings over 50% are really reflective.
Solar Heat Gain Coefficient (SHGC): When looking at labels attached to new windows and doors, this is the specification that NFRC (National Fenestration Rating Council) recognizes. It simply means the amount of solar energy that is released through the product (film or glass) after the energy has been reflected and absorbed. The lower the number, the less solar heat the product transmits. It is measured between 0 and 1, so it's actually a percentage.
Total Solar Energy Rejection (TSER): This has become the go-to spec for "heat rejection." It's the reciprocal of Solar Heat Gain Coefficient. For example: TSER of 70% is the same as SHGC of 0.30. Somebody a long time ago thought of using the opposite number of SHGC because it's easier for most people to relate better performance to a higher number. Hence, the invention of TSER. As a guideline, a TSER number in the 50% range means moderate performance, the 60% range means very good, and over 70% is excellent.
Glare Reduction: This is a percentage of visible light that is reduced by the film in addition to the glass. Your eyes will tell you a better story here than a number.
Solar Reflectance, Absorptance, & Transmission: These three numbers represent what the film is doing to the solar energy that's hitting it. The numbers will always add up to 100%. The absorption number is critical when determining if a film product is safe to use on particular windows. A general rule of thumb is that a film's absorption should not exceed 50% for dual-paned annealed glass with no low-e coating (see the Technical Stuff page). If there is a low-e coating on Side #3 and an interior window film is desired, a film with very low absorption (less than 35%) should be used to reduce risk of thermal shock.
Shading Coefficient (SC): This number isn't used much in this industry, but it has its relevance. It's simply a juxtaposition of solar heat gain through a window and the solar heat gain of the same window with a particular film. The lower the SC, the better the film is at reducing solar heat gain.
Emissivity: This number expresses the percentage (because it's measured between 0 and 1) of infrared energy (what we feel as heat) that is reflected back to the interior by the film. When you hear the term "low-e," it means "low-emissivity," or in other words: "low-emission." Remember that heat is energy and will disperse and flow toward where there is less energy, meaning a colder area. Think of fluid in this way. Fluid will spill and flow everywhere unless it's stopped or held by a barrier, like a container. When it's cold outside, the heat from your home or building will flow out toward the colder area. Plain glass has an emissivity of 0.84, meaning 84% of the infrared energy escapes through the glass and only 16% is reflected inward. A lower number means less winter heat loss.
Winter Heat Loss Reduction: This number is a mathematical result of the emissivity value of the film.
Winter U-Value: This is another specification that's not used too much in the window film industry unless we're talking about a low-e film for winter energy savings. It's a measure of heat transfer through the film and is the reciprocal of R-value (how insulation is rated). The lower the U-Value, the better the insulation qualities of the film.
Summer Solar Heat Gain Reduction: This is the percentage of solar heat energy that is reduced by the addition of a particular film. The higher the number, the better solar performance.
You're welcome to view all of the product specifications here.
I have noted the wishy-washy specification of IR rejection because it only pertains to specific wavelengths of the IR spectrum and not the entire IR spectrum.
Another truth-stretching specification is "On Angle" solar rejection. Every film and window will show better performance when the sun is hitting at an angle...as the sun normally does. This is not a true apples-to-apples representation of a film's performance and is not recognized by NFRC. If it was recognized by NFRC, it would be published on the certification labels on every window, door, and certified window film product. Solar Heat Gain Coefficient and its reciprocal Total Solar Energy Rejection are the real numbers recognized by NFRC and relate to solar energy hitting at a 90° angle, not at any other angle.
Some specification sheets will show data on single-pane glass and dual-paned insulated glass units. This is extremely confusing and I really wish the manufacturers would stop doing that. Compare films using the same row or column of performance data of the film on single-pane glass. This way you'll be sure to know the actual performance of the film itself independent of being installed on an unknown window.
And finally...if somebody cannot provide all performance data from the manufacturer, just tosses some film samples at you without any technical explanation, or simply can't explain the data, walk away and contact me.