Ok, This is my first foray into the DIY projector world. I've been reading through the forums for the last couple day'sand did not run across this topic.

My question is: Would Inert Gas Filled Double Pane Glass Work?

I'm just theorizing here: But wouldn't it reduce a lot of the heat reaching the LCD if you were to use the DPG and close off the lamp section.

Rather than using passive cooling, you can set it up like 2 seperate compartment's.

This way you can draw airflow directly across the bulb and in the other compartment draw air directly across the LCD panel.

Also with alot of the DPG i have seen you can get it with a UV reducing Low-E coating. Further reducing the heat transfer.

Just thought i would toss this out there.

Sure it works but light loss is a consideration

If someone sandwich the Fresnel Lens between two pieces of glass and enclosed it would the same thing happen?

I looked into this as well. It looks like a good idea, but...

1) Brain is right. Light loss is a serious consideration. The best figures I saw was 20% light loss (80% of the light gets through.)
2) Double-pane glass has to be built that way. This would have to be custom built and expensive. We already have this problem with single pane tempered glass.
3) Double-pane glass works in theory, but we're leaving a gap for air flow (cooling). This gap negates some of the performance of the DPG.

As alternatives, I also checked out:

1) Fireplace glass. Actually, a see-through ceramic. NeoCeram and PyroCeram would work, but are wicked expensive.
2) Tempered glass with an e-coating. This works, but is also expensive (but cheaper than ceramic).
3) Lexan. This is supposed to have the same insulation factor as an equivalent thickness of double-pane glass.

I ended up with Lexan because it is cheap, cuttable, and easy to get. I don't know how well it insulates, though. My pj doesn't get any cooler than people who are using tempered glass.

i used two piece of glass to sanwich my fresnel - so thats a total of 5 pieces of glass counting the tempered - my pics are not a good judgement - but in real life the image looks pretty good - of course i dont know what it looks like with out the glass

Check out my research and analysis of the effects of adding extra panes of glass to the basic design... conclusion: it DOES make a difference.

Extra glass investigation.

AllThumbs' figure for 80% light transmission on the dual pane thermal glass is about right. Each pane passes only 89% of the light that hits it. First pane reflects/absorbs 89% and the second reflects/absorbs 89% of what got through the first. Do the math: .89 X .89 = .7921... or ~79% reflection/absorbtion ignoring any IR or UV film that may be suspended in the void. It only goes downhill from there.

PS, Modest, your four extra panes result in a Lumen leven approximately 62% less than the lumen level without them.

maybe i can get rid of the two near the lense - the only reason i used the glass is so the fresnels would not bend from heat