# Performance of Solar Control Films on Building Glazing: A Literature Review
## 3 Solar Control Films
### Types of Solar Control Films  
The main industry players of window films (such as 3M [24]; Llumar [25]; Avery Dennison [26]; Solar Gard [27]; and Johnson Window Films [28]) offer a large variety of each type of SCF to be installed in different positions of the glazing system. Depending on their purpose, SCFs can be divided into the following types:  
* Reflective: these films have reflective properties on both sides that provide high heat, glare and UV control. They give a silvery/mirrored look to the glazing when viewed with indoor lighting or outdoor daylight. * Dual-reflective: these films have a reflective outside-facing layer with a subtler inside-facing layer, meaning they can provide significant solar control during the day and maintain a clear outside view at night. * Neutral: these films control solar gains through the glass while maintaining the original appearance of the glazing system. * Low emissivity: these films reduce the thermal transmittance coefficient (U-value) of the glazing system, increasing its thermal insulation and heat-rejection properties during the four seasons (suitable for temperate regions). * Spectrally selective: these films offer an excellent heat rejection with a virtually invisible appearance. Contrary to neutral SCFs, spectrally selective films can block specific regions of the solar spectrum associated with solar heat gains while not penalizing the transmittance of daylight through the glazing. * Ceramic: these films offer solar control without a metal layer, maintaining a low visible reflectivity and a high resistance to corrosion (suitable for coastal areas). * Safety and protection: these films can control excessive solar heat gains and, at the same time, increase the resistance of the glass pane to intentional or accidental impacts. In addition, this type of film reduces the amount and dimension of potential glass fragments and/or offers higher resistance to the glass to support shock waves from explosions and/or ballistic attacks. Information on the thermal and solar optical properties of the SCFs available on the market was gathered in this work to better understand the range of values of each property and help to highlight the differences between the multiple types of SCFs. The properties of the SCFs present in the International Glazing Database were collected using Optics [29] and Window [30] software. The International Glazing Database (IGDB) [31] encompasses the most extensive collection of products used for the construction of windows, namely: different types of glass, films, lamination adhesives, window frames, and filling gasses. It also contains detailed solar optical and thermal information on these products. The addition of products into the IGDB database follows a set of standards issued by the National Fenestration Rating Council. Adding a new film into this database requires that manufacturers provide film samples applied to single uncoated glass substrates with solar and optical transmittances greater than 0.83 and 0.89, respectively. These specifications ensure that the film has transmittance values similar to or lower than those of the glass to which it will be applied to [32]. The glass that meets these criteria: 3 mm single glass; 3 mm single glass with low iron content; and 6 mm single glass with low iron content. Additionally, manufacturers must submit samples of the same glass without the film, so that the thermal and solar optical properties of the glass can be determined separately. The version (v72.0) of the IGDB database [31] used for this work has, in total, 156 SCFs manufactured by some of the main industry players of window films (3M [24]; Llumar [25]; Avery Dennison [26]; Solar Gard [27]; and Johnson Window Films [28]). Figure 4 shows the quantity of SCFs assembled, grouped by film type. Figure 5 shows the ranges of the thermal and solar optical properties of different types of SCFs, present in the IGDB database [31], when applied to clear single glass (6 mm).