Everton drew 0-0 at Crystal Palace on Saturday and have not conceded a goal since Yannick Sagbo scored for Hull City on 19th October, a period lasting 330 minutes.
Roberto Martinez's side have given away just 10 goals this season, in 11 Premier League games, keeping six clean sheets.
Howard has started all 11 of those matches, as have Coleman and his fellow defenders Phil Jagielka, Sylvain Distin and Leighton Baines.
Asked by evertontv if such continuity was a key factor in their defensive stinginess, Coleman said: "It is. The lads are great and are very loud with their communication.
"It's important to keep a clean sheet and we did that. It's also important to create chances and score goals and we didn't do that, unfortunately, but it is a positive to keep a clean sheet.
"Maybe we have had to rely on Tim a little bit in the last two games. He has been brilliant."
Draw disappoints Coleman
However, the draw with Palace was Everton's second goalless stalemate in a row and Coleman admits there was a feeling that they should have left with more than a point.
"You've got to keep the ball of course, and that's something we do under the new manager," he said. "But you've got to keep it for a reason and that's to create chances.
"We didn't create enough for the amount of possession we had, it's as simple as that.
"We went to Palace playing well and with confidence so, with no disrespect to them, the way we're playing we should be going to those places and getting three points.
"It wasn't to be, though, because we just couldn't break them down."