It was 2-0 just three minutes later as David McGoldrick doubled his side's lead with an absolute screamer, bending the ball into the top corner with his left foot.
Rotherham's best chance to pull a goal back before the break fell to Alex Revell in the 19th minute when he collected the ball in the box unmarked, only to slice his shot and allow Chambers an easy block.
Ipswich should have gone further ahead just minutes into the second half as Conor Sammon stole a yard on the Millers' defence and slid the ball past Loach, only to see his effort come back off the post.
Mick McCarthy's side always looked the more likely to score in the second period, but Rotherham should have pulled one back in the latter stages as Christophe Berra was dispossessed by Kari Arnason and the Icelandic striker failed to hit the target with a clear sight of goal.
They could have made it three at the death when Frazer Richardson blazed the ball over from close range following a free kick, but McCarthy's men had to settle for two in the end.