In all of my years building PCs ESD has never been a problem. I have put machines together on shag carpet wearing a sweat suit before. The machine worked fine. ESD is mostly a throwback to the 1980's when components had much lower tolerances and you could fry them pretty easily. Nowadays the IC can take up to 10,000 volts from a static discharge or thereabouts. Not to say that you should build your pc in a thunderstorm while holding a metal pole in the other hand, but just touching the case every few minutes will be sufficient.