At a former job I worked from home where I had peace and quiet pretty much all day. I only really worked 4-5 hours in a day, but I was significantly (in the order-of-magnitude realm) more productive than my in-office teammates. On the occasion I'd go into the office for a few days my productivity level would similarly plummet, even though I was working for more hours each day. I can only attribute this to the incessant interruptions of the open-office plan.