Don't waste your time. The glass in thermopane windows isn't anything really special. It's the gas (or lack thereof) between the panes of glass that make thermopane windows better insulated. I'm not sure whether there's a gas or a vacuum in the windows.
From what I've seen, most window glass is really thin, like 1/8" thick tops. It won't support the water pressure necessary to build an aquarium from it. If you're set on building this tank, use at least 3/4" glass all the way around.
Glass is a good insulator by itself. There are a few reasons why thermopane windows are used instead of solid glass.
1. Cost - Compare the cost of a panel of 3/4" glass to the cost of a window with the same dimesions. The thick glass is way more expensive to make into a window.
2. Weight - Glass is really dense and heavy. My dad helped me disassemble a 10' tank made of 1" thick glass and I estimated the big panel (120"x24"x1") to weigh between 250lb and 300lb. Most people would struggle to open a window made of thick glass due to the weight.
3. Visibility - Thin glass doesn't distort light as much as thick glass. Colors are truer.