Term B is terrible to catch a few winks of shut-eye. Try Term A main check-in lobby. There are a few comfy chairs.

One used to be able to easily sneak into the Marriott Tower Suites, but with the remodel, that's now quite difficult.

BTW, IAH Management is about to undergo a regime change. Houston has a new mayor and the existing Airport Director just got caught red-handed over concession contracts.