Redmond, who previously had a reputation as a defensive batsman, reached his half-century off 23 balls and struck 13 boundaries from just 30 deliveries.
"When you've got nothing to lose you go out there and give it a go," he said. "I was pleased it came off. I got a couple in the slot early on and took it from there."
Scott Styris smashed 42 from 25 balls and Martin Guptil anchored the innings with an unbeaten 45 as New Zealand scored 198-5.
New Zealand ran out four Irish batsmen and Nathan McCallum took three wickets as Ireland were simply outclassed.
Redmond was only playing due to a spate of injuries in the New Zealand camp.
On Thursday he was named as a permanent replacement for Jesse Ryder, who is out of the tournament with an abdominal illness.
Regular captain Daniel Vettori failed to recover from a shoulder injury, forcing Brendon McCullum to stand-in, while Ross Taylor rested a hamstring strain.
This mini-crisis didn't seem to have any obvious effect on the Kiwis, who hit 32 from their first two overs and reached 50 from 28 balls.
One run later McCullum chipped an easy catch to Regan West off McCallan at mid-off.
Redmond was finally out lbw to Alex Cusack, but Styris and Martin Guptil put on 61 for the third wicket before the former was the victim of a tremendous diving catch by Kevin O'Brien off McCallan.
As New Zealand chased quick runs, Jacob Oram was caught by Andre Botha off Cusack for 15 and Trent Johnston bowled Peter McGlashan.
Ireland made a luckless start to the run chase, losing William Porterfield in the first over.
The Ireland captain was run out after the bowler, Kyle Mills, got his fingertips to a drive by Gary Wilson and deflected the ball onto the stumps.
Wilson was then dropped by Ian Butler at mid-on, but Niall O'Brien went in the third over, caught by Oram at mid-off off Mills.
Ireland were unable to score fast enough to threaten the New Zealand total.
Styris had Wilson caught by James Franklin for 28 and then ran out Andre Botha, before Kevin O'Brien was caught by Franklin off Nathan McCullum in the 11th over, with the run rate already over 13.
John Mooney was the third man to be run out after a direct hit by Brendon McCullum.
He then caught Cusack off his brother Nathan, who in turn trapped Kyle McCallan lbw two balls later.
Trent Johnston was the ninth man to go, run out by another direct hit from Brendon McCullum and the rout was completed when Kyle Mills bowled West in the 17th over.
Porterfield admitted his side had been well beaten.
"The first five overs were crucial," Porterfield said. "They got away. They fielded really well. They didn't make it easy for us. Our preparation has been good and we will learn a lot from the Super Eights."
