Any form of tint will raise the temperature of glass to some degree since tinting absorbs light energy creating heat. LowE is designed to reduce (not eliminate) the stress on glass by reflecting instead of absorbing some of the heat from direct sunlight. It is rare that tinting alone will cause breakage. I suspect most breakage is due to compromised glass from flexing, a rock peck, or a manufacturing issue. Temperature change is nearly always involved although one of the other factors is usually the culprit. From 3M's website:
Will Window Films Cause Glass to Break?
Glass breaks when stressed. There are five types of stress that may cause glass breakage:
- Thermal Stress - from absorption of solar radiation.
- Tensile Stress - from the weight of the glass itself.
- Mechanical Flexing Stress - from wind.
- Impact Stress - from flying objects, (hail, baseballs).
- Twisting Stress - from building or window frame sagging or settling.
The first type, thermal stress, is the only one which film may affect. The use of window films will increase the thermal stress on sunlit glass. However, there are also other factors which will increase thermal stress such as: partial shading of windows from overhangs, tightly fitting drapes or blinds, signs or decals on windows, heating and cooling vents directed at glass. In addition, different types of glass (annealed versus tempered, clear versus tinted) have different solar absorption rates and will withstand different degrees of thermal stress.
I would think a light tint that is as mirror-like as possible would be relatively safe and effective on a sunroof. It would also prevent the tempered glass slivers from raining down into the cab if the sunroof burst. I had a panoramic roof in a Murano burst on me. It felt like a bomb went off and glass shards fell onto the shade since it was closed.