Double-pane windows

Why don't cars have dual-pane windows? It would help tremendously to keep the occupants cool in those hot sunny summer days, and it would help insulate in the winter as well. Anybody have a good answer?

Glass adds weight. It also adds cost. You would be surprised to find out that window thickness is a significant discussion point in engineering as it impacts so many other things. Stronger motor to raise/lower the window. This requires heavier gauge wiring. Etc.

johnr said:

Why don't cars have dual-pane windows? It would help tremendously to keep the occupants cool in those hot sunny summer days, and it would help insulate in the winter as well. Anybody have a good answer?

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Older body style (1990s) Mercedes S class had them. They're great; loved them. Problem: cost & weight. The extra weight also means more costly and heavier motors (unless you'd like to hand-crank?). Times four, of course. Other reasons accounted for part of it, but the weight loss when the 2000 body style came out, despite other improvements and add-ons: 500 pounds! (Not, of course, just because of the windows, which went from dual-pane to slightly thicker than normal, but single pane.)

Ok, double pane windows would add significant weight and cost, but it seems the advantages would make it worth it. I guess tinted windows would help some, but double pane would save so much energy on climate control and make it more comfortable.

I thought most modern car windows ARE double-pane, in that they are laminates. That is how they control sun fading (UV filters). Not in the glass, but in the very thin layer between the two sheets of window glass. Which is also there for shatter control.

They just don't have an air gap.

Is this not how car windows are currently made?

Dav said:

I thought most modern car windows ARE double-pane, in that they are laminates. That is how they control sun fading (UV filters). Not in the glass, but in the very thin layer between the two sheets of window glass. Which is also there for shatter control.

They just don't have an air gap.

Is this not how car windows are currently made?

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I'm sure that's the deal for windshields. Side and rear windows aren't laminated but they do use tempered glass like the windshield. Tempered glass breaks into small pieces that are much safer than the long shards (daggers!) natural glass breaks into.

Dav said:

That is how they control sun fading (UV filters).

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Not all manufacturer's use UV glass. Nissan does, and I'm confident will use it in the LEAF to keep interior temperatures lower.

LEAFguy said:

Dav said:

That is how they control sun fading (UV filters).

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Not all manufacturer's use UV glass. Nissan does, and I'm confident will use it in the LEAF to keep interior temperatures lower.

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I've never seen UV glass (Honda/Toyota)...is it darker than regular factory tinted glass? Would you still need to add tinting from the dealer?

I think most glass does not pass all the UV, but does pass an annoying percentage.

An additional UV filter in laminated auto glass is usually not in the glass itself, but in the "glue" that holds the two "laminated" layers together. However, usually only the front windshield glass is laminated.

I do not know what is done to the other glass to make it absorb more UV. Does anybody?

garygid said:

I think most glass does not pass all the UV, but does pass an annoying percentage.

An additional UV filter in laminated auto glass is usually not in the glass itself, but in the "glue" that holds the two "laminated" layers together. However, usually only the front windshield glass is laminated.

I do not know what is done to the other glass to make it absorb more UV. Does anybody?

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Exactly right gary, the layer has the UV, the layer is to hold the tempered glass together. Laminated glass has higher STC ratings for sound but is much more expensive, having "dual pane" in a car is complex due to the shapes and space between the panes. Laminate is very strong but more expensive and used for code in overhead situations in skylights and for security doors to prevent intrusion. Tempered is required in areas where the glass is below a specified elevation or near an entry door. Presently I'm having some very large 5X8' sheets of specialized glass tempered for safety. Laminate is the ultimate for sound and strength but is very costly. There are many UV coatings available for reflection with heat retention like Low E on all glass windows. For cars there are great tints to reduce heat as discussed previously.