“Glazing improves [fuel] efficiency by 3%.”
Climatewire reports:
A specific window-glazing technique that increases fuel efficiency has drawn renewed criticism from an unfamiliar player in automobile standards — the telecommunications industry.
CTIA-The Wireless Association — the trade association representing wireless carriers, equipment manufacturers and Internet service providers — is concerned that fuel economy regulations would encourage the use of a specific energy efficient window-glazing technology that could block wireless reception in vehicles.
The window technology in question is called metalized glazing, a technique for windows, windshields and moon roofs that reduces the amount of sun’s heat that enters cars. Glazed windows are manufactured by adding a very thin layer of metal particles from zinc, cadmium and indium that reflects solar radiation.
This layer can also block radio frequencies for cellular phones, GPS navigators and other wireless devices.
Glazing can reduce the temperature inside a car by up to 9.7 degrees Celsius, translating into an emissions reduction of 2.9 to 3.9 grams of CO2 per mile, according to EPA and NHTSA’s technical support document for CAFE standards. The standards do not specify metalized glazing over other types…
That 3% assumes a steady hot climate and daytime driving and running and AC. It would be much much less in reality.
The additional fuel efficiency is nice (although I’d like to see verficiation of the claim), but I’ve got to say that the reduction in radiant heat load makes the car much more comfortable. WHich I suspect is why lots of people look for it.
Automotive window glazing is restricted in many jurisdictions for safety reasons. It is EXTREMELY important for police officers, when approaching a vehicle during a traffic stop, to be able to see what the occupants may be doing in those critical seconds before the policeman steps into a possible range of fire for a handgun. This need trumps an alleged 3% benefit in fuel efficiency.