Frenchman's side have conceded 11 goals in four games
Villa have conceded 11 goals in their last four games and Houllier wants the idea of keeping a clean sheet to become an obsession.
“At the back we need a bit of both - a change of fortune and of form," Houllier told reporters.
"We've conceded 11 goals in four games. It's not good enough for a team of our standard.
"We have to get into the games with the idea of keeping a clean sheet because when you keep a clean sheet you give yourself a chance to win.
"Keeping clean sheets has been an obsession of mine in my career."
Houllier has also admitted it is not just defensive lapses which is costing his side. The former Liverpool manager insists it is not just his defenders who need to take the blame. He believes his strikers need to be more clinical.
He said: "I won't tell you what I put our defensive problems down to. I think it is collective really. We need to be better.
"We obviously need to eradicate some stupid, schoolboy errors at the back which cost goals.
"But we also need to improve in the final third and we need to be more clinical.
"We are improving in terms of our passing, movement and preparation although there are some areas where we have to keep improving.
"We need more of a cutting edge and to be more clinical at times."