Does Laminated Glass Block Heat? Standard vs Solar Control

Heat inside the car: what standard laminated glass blocks

Standard laminated glass blocks a small share of solar heat, and most infrared still reaches the cabin. A laminated windshield is two pieces of glass bonded by a polyvinyl butyral (PVB) interlayer. The PVB exists for safety, and the page on what laminated glass is covers that build in detail.

Sekisui, a PVB maker, lists clear glass with standard PVB at 77% direct solar transmission. Eastman, another PVB maker, gives 87% as typical for a single sheet of clear glass. The two figures come from separate documents, so the gap is only a rough guide. Part of it also comes from having two sheets of glass.

The rest of the heat story happens inside the cabin. Sunlight warms the dashboard, seats and steering wheel once it passes through the glass. The windshield is a major entry point. An NREL and Eastman paper says more than 40% of the heat entering a vehicle comes through it. California Air Resources Board (CARB) staff put the windshield share at about half for vehicles without a glass roof.

TTS figures by glass type

Total solar transmittance (Tts, often written TTS) ranges from 62% for a green-tint windshield to 32.5% or less for a reflective sunroof laminate in the data below. CARB staff define Tts as the solar energy that passes through the glazing, including energy absorbed and re-radiated to the interior. ISO 13837 is the test standard for it.

Direct solar transmission counts only the energy that passes straight through. It reads lower than Tts on absorbing glass, so the two numbers cannot be compared. Each row below keeps its own measure and test conditions.

Glass build	Visible light	Solar figure	Conditions and source
Clear, standard PVB, clear	89%	77% direct	Sekisui catalog; method and thickness not stated
Clear, solar control film, clear	87%	65% direct	Sekisui catalog; same limits
Green, solar control film, green	77%	47% direct	Sekisui catalog; same limits
Green-tint windshield	Not published	Tts 62%	NREL and Eastman, SAE 2013-01-0553
Saflex S series solar PVB windshield	Not published	Tts 55%	NREL and Eastman, same paper
Saflex Evoca XIR.SR sunroof laminate	46%	Tts 32.5% or less, direct 24% or less, reflected 43% or more	Eastman lab data, ISO 13837 (2021), 2.1 mm clear glass plies

Federal rules use the same yardstick. EPA’s off-cycle credit rule sets a Tts baseline of 62 for windshields and side windows, and 40 for roof glass, measured under ISO 13837. Automakers can earn a greenhouse-gas credit for glass that beats the baseline. The rule does not require any Tts level.

UV blocking vs infrared: why 99% UV is a different number

UV blocking and heat blocking are separate properties, and high UV blocking says almost nothing about heat. The International Window Film Association (IWFA) puts the sun’s radiant energy at 44% visible light, 53% infrared and 3% ultraviolet. Removing nearly all UV therefore removes only a small slice of the total energy.

Standard PVB handles that small slice well. Eastman states that conventional Saflex PVB screens 99% of UV up to 380 nm. The full numbers are on the page about whether laminated glass blocks UV rays. That figure explains why many search results quote “99%” for laminated glass. The 99% describes UV only.

Visible light cannot carry the load either. FMVSS 205 requires glazing in a new passenger car to transmit at least 70% of light, as a NHTSA interpretation states. Infrared is the band left to work on, and it holds more than half the energy. IWFA warns that an infrared rejection rating has no defined test method, so one company may measure 780 to 2,500 nm and another 900 to 1,000 nm. Tts and total solar energy rejected are the safer numbers to compare.

Solar or IR-reflective laminated glass and film

Laminated glass controls heat through two routes: absorbing infrared in the laminate or reflecting it back out. Absorbing interlayers hold infrared inside the laminate. Eastman says its Evoca S series uses nanoparticles for IR absorption. Its Solar Connect PVB is tuned to 25% transmission at 850 to 900 nm so sensors and head-up displays keep working.

Reflective laminates turn infrared away before it reaches the cabin. AGC’s Iris glass places an invisible coating inside the laminate. Pilkington says it can make a coated windshield that reflects more than 30% of the sun’s energy, over five times a standard glass. PGW said Sungate windshields reflect or absorb about 50% of solar energy, as reported by Just Auto in 2013. Eastman claims Saflex XIR improves total solar transmittance by 25% over its S series.

Film is the retrofit route, because an interlayer cannot be added to finished glass. LLumar lists its clear AIR 80 film at 77% visible light and 43% total solar energy rejected, tested on 6 mm clear glass under NFRC guidelines. That test differs from ISO 13837. IWFA calls high-light nanoceramic films good candidates for windshields where legally allowed. Check what car window tint is legal first, and see ceramic windshield tint for film types. IWFA also notes that highly conductive films can interfere with radio and phone signals.

Laminated vs tempered glass for heat

Lamination alone is a minor heat factor, because solar performance depends on what is in or on the glass. The wider comparison sits on the page about laminated glass vs tempered glass.

Tempered glass controls heat mainly through its body tint. CARB staff say materials added to molten glass let tempered glass moderately reduce solar heat gain. Pilkington says its green Optikool and EZ-KOOL glasses cut heat entering through the glazed area by about 20% compared with standard tinted glass.

Laminated glass has more options because it can protect a film or coating between its plies. CARB staff said that all-around 40% Tts would need laminated glazing with the technology of 2009. Pittsburgh Glass Works told CARB in 2009 that it could produce windshields below 40% Tts. It also argued that better performance was achievable in both laminated and tempered builds.

CARB cited a Fiat test that shows the size of each step. After a two-hour soak in a Punto, cabin air reached 65°C (149°F) with standard glazing, 60°C (140°F) with absorbing glazing and 58°C (136°F) with infrared-reflective glazing. CARB staff read the gap between absorbing and reflective glazing as about 2°C (3.6°F).

What solar glass changes in a real car

A solar-control windshield changes surface temperatures far more than air temperature. NREL and Eastman tested this on two white 2011 Toyota Corollas in Golden, Colorado, in September 2011. The cars sat parked facing south with windows closed, on days above 700 W/m2 of sunlight and below 3 m/s of wind. Results are the 12:30 to 13:30 average.

Location	Change from Tts 62% to Tts 55% windshield
Average cabin air	1.9°F cooler
Air at breath level	2.1°F cooler
Dashboard	6.3°F cooler
Steering wheel	9.6°F cooler
Windshield	3.0°F hotter

The windshield warmed up because absorbing glass holds the heat it stops. Eastman’s glass properties for that paper show solar-weighted transmission falling from 53.61% to 39.23% and absorption rising from 39.49% to 54.32%. The study’s simulation found 4% less air-conditioning capacity needed. It estimated 0.7% to 1.1% better fuel economy and 0.7% to 1.5% more EV range. The authors say real-world results will differ.

Reflective glass showed larger gaps in some earlier tests. CARB reports NREL results of 6.7°C (12.1°F) lower breath air with a Sungate EP windshield on a Cadillac STS and 2.2°C (4.0°F) with Sungate on a Ford Explorer. CARB staff tied the Explorer’s modest result to a production windshield that already absorbed solar heat. AGC claims up to 15°C for Iris, depending on conditions.

How to tell which glass your car has

The glass label, the tint and the owner’s manual together show what your car has. A solar windshield and a plain green one can look alike from the driver’s seat, so a short check helps. Start with the page on how to check a laminated windshield if the side glass is the question.

Metal coatings carry a trade-off. Saint-Gobain and Escort both describe coated glass acting as a Faraday cage that blocks radio signals, and the guide to heat insulating glass covers toll tags and radar. CARB dropped its Cool Cars glazing rule on March 25, 2010, after stakeholders raised concerns about electronic devices. Eastman markets PVB-based Solar Connect as signal friendly. A replacement windshield should match the original’s solar specification, so ask the shop before ordering.

Frequently asked questions

Does a laminated windshield keep a car cooler?

A standard laminated windshield adds little cooling. Solar-control versions help: NREL measured 1.9°F cooler average cabin air and a 9.6°F cooler steering wheel in a parked Corolla with a Tts 55% windshield.

Is laminated glass better than tempered glass for heat?

Lamination alone makes little difference, and body tint does much of the work on tempered glass. Laminated glass has the edge at the top end because it can hold reflective coatings and films between its plies.

What is a good TTS for a windshield?

EPA uses Tts 62 as the baseline for windshields, so a lower figure beats that baseline. CARB proposed 50% for 2012 model-year windshields in a rule it later dropped, and PGW said in 2009 that it could reach below 40%.

Does solar control glass make the car colder in winter?

NREL says glazing does not affect winter fuel economy in a conventional car, because engine waste heat warms the cabin. Its paper also says cabin heating is designed for night driving with no sun, so a properly designed heater keeps comfort unchanged.

Can I add heat protection without replacing the glass?

Yes. A clear or ceramic film is the usual retrofit, and the page on whether car window tint helps with heat compares the options. A parked car can also use a shade, covered in do windshield sun protectors work.

Sources

• Rugh et al. (NREL and Eastman), Impact of Solar Control PVB Glass on Vehicle Interior Temperatures, SAE 2013-01-0553
• California Air Resources Board, Cool Car Standards, Appendix C, May 8, 2009
• California Air Resources Board, Cool Cars Initial Statement of Reasons, 2009
• California Air Resources Board, Statement on Cool Cars Regulation, March 25, 2010
• Pittsburgh Glass Works, comments to CARB, June 15, 2009
• 40 CFR 86.1869-12, off-cycle credits, checked 2026-10-31
• NHTSA interpretation on FMVSS 205 light transmittance, checked 2026-10-25
• Sekisui S-LEC Solar Control Film catalog (ArchiExpo copy), checked 2026-10-31
• Eastman, Saflex Evoca XIR.SR product bulletin
• Eastman, Saflex solar-absorbing PVB interlayers
• Eastman, Saflex XIR
• Eastman, Saflex Solar Connect PVB, 2020
• Eastman, Saflex UV
• Pilkington, Solar control in vehicles
• AGC Automotive, Infra-red Cut Glass Iris
• International Window Film Association, Automotive Education Guide 2026
• LLumar Window Film Performance Data, 03/26
• Just Auto, Research analysis: infrared reflective glazing, 2013
• Glass.com, Metallized Windshield: What is it, 2017
• AAA, Vehicle Escape Tool Evaluation, 2019
• Saint-Gobain patent US8022333B2
• Escort support, metallic-coated windshields