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Date:         Wed, 20 Jul 2005 23:59:08 -0700
Reply-To:     Doug in Calif <vanagon@ASTOUND.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Doug in Calif <vanagon@ASTOUND.NET>
Subject:      Re: Window Tinting - What Really Works? - cooling,  shades,
              curtains, solar gain
Comments: To: "Matthew C. Huntley" <matthew.huntley@STRATHBOGIE.NET>
Content-Type: text/plain; charset="iso-8859-1"

Group,

All of my reading and testing with various window tints has all taught me that dark tints super heat the glass and thereby super heat the air inside the van.

The reason a car heats up in the sun is due to a process called "solar gain" The car windows act as one way valves to allow sunlight through and once it strikes a dark object inside the vehicle it is absorbed and the energy wave changes into heat. The heat is no longer a "light wave" of energy and can no longer pass back out through glass, so the build up continues.

When sunlight strikes a dark colored object the heat energy is absorbed, a light color will reflect the sunlight and not absorb it or convert it to heat. This is why the body of a white car sitting in the sun will be the same as the air temp when you put your hand on it and a black car right next to it can literally fry an egg. A light colored curtain in the window or a foil type windshield sun shade reflects the "light" back out as "light" not allowing it to be absorbed. If everything inside of your car was bright white or a foil fabric it could reflect most or all of the light back out of the glass and it would not have much "solar gain".

The problem with dark tints is even though they do stop the light from entering the vehicle they ABSORB the light at the surface of the glass like the paint on a black car does, because the glass is now a dark color. The glass itself also has a great deal of thermal mass, its heavy and dense so it can store lots of heat, like a black rock or hunk of black steel vs. a black piece of wood in sitting in the sun. This even means once your AC cools the air inside your van, you still have the weight of the glass to cool down which takes far more energy than if the fabric on your seat (which has little thermal mass) stopped the light, . There is so much glass in the vanagon that it does a pretty good job of making an oven out of your bus.

An easy and effective solution while parked is a light colored (white curtain) or mirror (bubble foil) to reflect the heat back out the glass. This does not allow anything inside the van to absorb the sunlight, even if there are some dark colors in the curtain it has little thermal mass. The glass will stay at a much lower temp.

Mirrored tint helps to a degree but they add dark pigments to it and the dark pigments absorb heat. I have personally tinted several of my vanagon windows with both dark limo tint and even mirrored bronze and gold tints, and removed them every time because they heat the glass too much for me with no AC.

True silver mirrored tint would absorb less or none but looks like mirrors. Ceramic tints though expensive do the best job of not allowing the heat wave energy to penetrate the glass and being a ceramic don't hold or absorb heat. They are by far the best to see out clear glass and reject solar gain.

A light colored curtain in the window works extremely well but you cant see out.

My first van an 85 sunroof was painted factory dark navy blue and had no factory AC. It was such an oven on hot sunny days that I eventually painted the whole van white on the outside which made a huge difference. I tried every kind of tint I could find and ended up making my own custom shades to block the heat and gain privacy. I ended up making shades out of Plexiglas and painting 50% of it white to create a venetian blind effect. It worked pretty well at blocking the heat, (and cold btw). Here's a couple pics of the 85 with the custom the shades.

http://users.ca.astound.net/dougfayne/85sunroofvanagonpic3.JPG

http://users.ca.astound.net/dougfayne/85sunroofvanagonpic1.JPG

Currently on my 87 syncro which also has no factory AC and is the Dove blue color (still hot in the sun) I made custom shades using a screen fabric material called Suntex. It is developed solar heat rejection for homes and RVs. It usually goes outside the glass. http://www.phifer.com/suntex.htm

It comes in various colors I chose the gray color and painted white stripes on the outside with Krylon. I attach it with snaps on all the windows during the summer. I also have the westy curtains because at night you can see right through into the van when lights are on. It also adds insulation from the glass when its cold outside.

Here's some pics

http://users.ca.astound.net/dougfayne/SuntexFabriccantseein.JPG

http://users.ca.astound.net/dougfayne/Suntexlookingoutslider.JPG

http://users.ca.astound.net/dougfayne/Suntexpoptopup.JPG

http://users.ca.astound.net/dougfayne/Suntexlookingoutrearhatch.JPG

http://users.ca.astound.net/dougfayne/SuntexandDpillarsliders.JPG

Doug

----- Original Message ----- From: "Matthew C. Huntley" <matthew.huntley@STRATHBOGIE.NET> To: <vanagon@GERRY.VANAGON.COM> Sent: Wednesday, July 20, 2005 8:58 PM Subject: Window Tinting - What Really Works?

> I am looking into tinting the windows on my '86GL. > I Really want to cut the amount of heat that the car retains during the > day. > I have have heard 2 stories on tinting the windows, Either it helps cut > down the heat, or the tint picks up the heat, and radiates it into the > car. > > which one is true? > > Thanks All, > Matt


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