Jordan James celebrates scoring one of Wales' tries against Ireland
Wales came from 12-0 down in Pontypridd on Sunday to condemn Ireland to their heaviest defeat for eight years and reach the final of the European Cup.
Wales face Scotland in next Sunday's final in Bridgend, while the Irish face a third-place play-off against Lebanon.
Ireland took the lead with tries from Marcus St Hilaire and Liam Finn, both goaled by Pat Richards.
But Wales drew level by the break as Ian Webster and Lee Williams crossed, then let rip in the second half.
The home side seized control of the game with three tries in a decisive 10-minute spell early in the second half through Rhys Williams, Ashley Bateman and Geraint Davies.
Lloyd White missed all three conversions having kicked the extras for both the first-half tries, leaving Ireland with a sniff of a recovery.
But prop Jordan James, leading Wales on his 16th consecutive appearance in the absence of injured captain Ben Flower, clinched victory when he powered his way over on 61 minutes.
Full-back Elliott Kear and substitute Gil Dudson then took advantage of a tiring Irish defence to add further tries and White took his goal tally to five from eight attempts.
Wales coach Iestyn Harris:
"I thought we were a bit scrappy for the first 30 minutes and we dropped a lot of ball.
"I said a few things to them at half-time to try and help them and get a better performance from them in the second half, and I think that worked.
"The skill levels in the conditions were very high and we played some good rugby and tested the Ireland defence. That's all I asked of them and they played some good rugby as well.
"We wanted to lift the tempo of the game today, our defensive line was aggressive and fast and we played with some skill, all of which were very important.
"We tested them around the ruck and put width in our passes. Our kicking game was good too, I was very pleased."
Ireland coach Andy Kelly:
"We can't complain or be aggrieved at anything today, we were outplayed by a much better and enthusiastic side and paid the penalty.
"We struggled to get hold of the ball in the second half and when we did, we didn't do much with it.
"Their forwards dominated our pack and it cost us the game. They also defended well, we were being dominated in the middle of the field.
"Pride is the first port of call for us this week. The players need to look at themselves and recompense themselves for the way they played today.
"We've got some structural things to work on and what we can't afford to do is be dominated in the forward line like we were today. That's the engine room and it didn't fire."
Wales: Elliot Kear (Celtic Crusaders), Rhys Williams (Warrington Wolves), Matt Thomas (London Skolars), Christiaan Roets (Bridgend Blue Bulls), Ashley Bateman (Celtic Crusaders), Lloyd White (Celtic Crusaders), Ian Watson (Leigh Centurions), Jordan James (Celtic Crusaders), Neil Budworth (Celtic Crusaders), Gil Dudson (Celtic Crusaders), Chris Beasley (Celtic Crusaders), Geraint Davies (Celtic Crusaders), Ian Webster (Central Comets).
Subs: Lee Williams (Celtic Crusaders), Ross Divorty (Featherstone Rovers), Matt Barron (Gateshead Thunder), Lewis Mills (Celtic Crusaders).
Tries: Webster (31), L.Williams (38), R.Williams (48), Bateman (53), Davies (56), James (61), Kear (64), Dudson (72)
Goals: White 5/8
Ireland: Karl Fitzpatrick (Salford City Reds), Tim Bergin (Laois Panthers), Marcus St Hilaire (Oldham), James Haley (Halifax), Pat Richards (Wigan Warriors), James Coyle (Wigan Warriors), Liam Finn (Dewsbury Rams), Ryan Boyle (Castleford Tigers), Bob Beswick (Halifax), Luke Ambler (Leeds Rhinos), Sean Hesketh (York City Knights), Dave Allen (Barrow Raiders), Tyrone McCarthy (Warrington Wolves).
Subs: Wayne Kerr (Oldham), Paddy Barcoe (Carlow Crusaders), Mike Haley (Leeds Rhinos), Stevie Gibbons (Carlow Crusaders).
Tries: St Hilaire (8), Finn (19)
Goals: Richards 2/2
Referee: Thierry Alibert (France).