Chapel is probably your best bet. IAH isn't a great airport for sleeping in. If the chapel doesn't work out, I'd go over to the Terminal D gates. Place is quiet as it's a ghost town after 7-8 pm, once the flights to Europe and the Middle East leave. The one time I slept at IAH that's where I camped out.

Check this out; one of the recent reviews recommends Terminal A, as well as the connector between the two sides of A.

http://www.sleepinginairports.net/li...H#.VujS5-IrJD8