A car's solar control glazing system is one which selectively absorbs, reflects and transmits solar energy to help keep the occupants comfortable, protect the interior and lesson the requirement for air conditioning, thereby reducing fuel consumption. Matthew Beecham reports on some trends occurring in the automotive infrared reflective (IRR) glazing market.

Infrared reflective windshields are popular in vehicles, used to enhance thermal comfort and increase air conditioning efficiency. A number of glassmakers are therefore offering this type of coating, marketing it under various guises.  For example, Pittsburgh Glass Works' (PGW) so-called Sungate windshields are produced from two pieces of glass with a vinyl interlayer sandwiched between.  The outer glass has a transparent metallic coating that reflects solar infrared heat while transmitting visible light.  As a result, Sungate windshields reflect or absorb about 50 percent of the solar energy striking the glass.  The aesthetics of the coating can be changed to give it more or less colour to coordinate with the vehicle's paint work. PGW further claims that tests have proved that installing Sungate can increase a vehicle's fuel efficiency by up to four percent.  

In observing demand for IRR glazing, Pete Dishart, PGW told just-auto: "In Europe [IRR windshields] were launched on smaller vehicles back in the days when air conditioning were not so prevalent. The heat load reduction was therefore a very effective way of dealing with passenger comfort in a car that didn't have air conditioning. Today, we see it being offered in all car segments. The major difference between the upscale ones and the lower segment cars is that in the upscale segments they are offering IRR glazings in all locations around the car. For example, Mercedes-Benz S Class and Audi A8 have IRR glazing in all positions - windshields, doors and backlites; that itself is not very common in lower segments cars."

For its part, Eastman Chemical offers a metallic reflective film that is embedded between the PVB interlayers, as Matt Rose, Global Automotive Market Manager, Advanced Materials-Interlayers, Eastman Chemical told us: "Eastman offers XIR automotive film, which is a spectrally-reflective metallic coated film that is embedded between layers of Saflex PVB interlayers. Europe is really the only place in the world where IRR technologies are used on a large scale. Although the primary driver has always been passenger comfort, the tightening of environmental regulations is furthering the need to look for ways in which to reduce air conditioning usage and CO2. Another notable driver [of heat reflective glazings] is the increase in electric and hybrid vehicles. Although EVs and hybrids comprise a relative small portion of the overall vehicle market range extension is extremely important with such vehicles, especially when it comes to EVs. For example, the Tesla Model S has solar controlled glazing on the panoramic sunroof, backlite and windshield. OEMs understand that it is of critical importance to reduce as much heat into that car so they can get the range extension that the market needs."

Robert Vandal, Vice President of Product Engineering and Development, Guardian Automotive reckons that the EU reached a peak with IRR installations by the early 2000s through mid-2000s but fitment rates have begun to wane since then. "The higher segment cars still offer it as either standard or optional. Our main consumers of IRR windshields include Volkswagen (Passat Coupe), Audi (A6 and A8), Porsche, BMW (X3, X5 and X6), Porsche (Cayenne and Panamera) and Bentley (Flying Spur)." Guardian's so-called SilverGuard comprises a family of nano-particle thin film coated laminates that provide high levels of solar energy reflection while selectively transmitting visible light. The coatings can be combined with a variety of glass substrates to achieve the full range - from maximum visible transmission and solar reflectivity to privacy-type light transmission combining solar reflectivity with absorbing solutions to achieve very low transmission levels.

Meanwhile, Giovanni Occhionorelli, Marketing Manager, AGC Automotive supports the belief that the trend for IRR windshields is less popular than before, mainly due to cost reasons. "Yet [IRR] is quite necessary for cars with large windshields and cars with specific air conditioning issues. Here, we see higher fitment rates amongst certain upper- and mid-range vehicle models."

In terms of the forces driving the use of IRR, Mukesh Rustagi of PGW believes that the biggest issue is not the safety regulations but the fuel economy regulations that are coming into play in North America, i.e. NHTSA CAFE regulations, He told us: "This year, EPA issued some CO² regulations marking the first time that it has been given the authority to specify emissions on cars directly. Until now that authority lay with NHTSA for fuel economy regulations. So now with the EPA regulations, specifically the ones that are in place for model years 2017 to 2025, these provide 'credit' for IRR glazing and, in turn, could promote the wider use of IRR."

Vandal added that, of course, these driving forces include emissions, fuel savings, air conditioning load and occupant comfort. "Over the past decade or so there has been improvements in solar reflective glazing performance but we have also seen improvements in its appearance. Coatings have matured to the point where such off coloured visible reflectives are less noticeable while offering far better solar reflective performance."

And in terms of the extent to which IRR glazing is appearing on side and rear windows, Occhionorelli believes that this market is still small for side and rear window applications, adding: "I would say the laminate sidelites have moved more in the direction of laminated acoustic hence using an acoustic inter-layer than IRR. But there are still vehicle models encased with IRR glazing, such as the Mercedes S class."

Rose concluded: "We see [IRR] primarily in the windshield due to the fact that about 40% of the heat enters the cabin through this area. But we are starting to see more and more IR reflective materials in the side glass. Also, OEMs are recognising the fact that laminated glass on the side has other benefits. In addition to the ability to improved infrared performance, it makes the cabin quieter through its acoustic characteristics, which allows OEMs to increased the functionality of the glazing while improving passenger comfort."