"It was an important win against a very good side," Fergie said after the 1-0 win at Upton Park.
"It was a fantastic atmosphere. They really get behind their team.
"Upton Park's always been a difficult place for us to come in the past to so that's why we chose experienced players like Ryan Giggs and Paul Scholes.
"It's also good to have former West Ham players like Michael Carrick and Rio Ferdinand in your side.
"We played some fantastic football. We're an attacking team but the back four are really concentrating on their jobs and they're quick, that's very important.
"The clean sheets have been a topic, but it doesn't just change the emphasis on our game.
"I'm pleased for Edwin van der Sar. At his age he's achieved everything but he's still excellent and determined to keep the clean sheet record going."