The former national Twenty20 batsman smashed a stunning unbeaten century at a strike-rate of 155 to lead Brisbane to an imposing 3-183 before the Renegades capitulated despite four dropped catches from Heat fielders.
Table-topping Renegades were held to 9-168 in a brave reply.
Brisbane now play in the prestigious grand final against the winner of Perth and Melbourne Stars on Wednesday night.
Brisbane finished fourth on the Big Bash table and will travel to either Perth or the MCG for the grand final.
Grand finalists qualify for the $13million Champions League in South Africa or India in October.
Pomersbach, 28, is rebuilding his troubled career in only his second season in Queensland and the Heat.
He smacked a season-high 112 from 70 balls and brought up his ton from only 65 deliveries.
His second 50 was hammered from just 30 deliveries.
The powerful left-hander smashed 15 fours and two sixes in posting his ton and only the second century of the Big Bash this summer.
The Renegades, who only lost one game in clinching top-spot on the ladder and their home ground final, had to score at 9.2 runs an over to post the biggest run-chase tally of the tournament.
They appeared on course to potentially run-down the big winning total at 3-97 when international hopeful Dan Christian went for 24 off his second over and 12th of the innings.
But Australian borderline limited-overs seamer Ben Cutting dismissed Tom Cooper (14) in the next over as the impressive seamer finished with 3-25 with 12 balls the aggressive Renegades could not score from.
Only Perth had previously scored more than 180 in this summer's Big Bash batting and the Scorchers achieved the tally twice, with one occasion a batting first 3-187 to beat the Renegades on December 29 at the WACA.
Stylish Heat right-hander Joe Burns was also in on the big-hitting act with 33 from 28 balls, including the first six of the innings in the eighth over off big quick Darren Pattinson.
Pomersbach and Burns shared a vital 80-run partnership for the second wicket.
It was the third time the one-time bad-boy of Australian cricket had crossed 50 for his adopted franchise after a succession of disciplinary dramas at his home state of Western Australia.
Pomersbach hammered Heat into the semi with a competition-fastest half-century on Saturday when he smashed 82 from only 42 balls.
His 50 in that swashbuckling display came up in only 24 balls.
World champion finger spinner Mutiah Muralitharan was injected into the Renegades attack immediately after the first six overs and powerplay ended.
The world-record Test wicket-holder had an instant impact with a big leg-before-wicket shout on aggressive right-hander Joe Burns.
Muralitharan went for an unusually expensive 1-35 from his four overs.
The Heat won the toss and elected to bat on what appeared a dry and potentially flat pitch with a porojected score initially in the region of 160.
Brisbane suffered a disastrous setback just prior to the toss when captain and former international all-rounder James Hopes suffered an injury in his warm-up and had to withdraw from the clash.
Hopes strained his hamstring going through his last minute bowling preparations and technically may not have been replaced in the starting line-up with official team sheets already lodged.
Hopes declared in a Fox Sports interview during play that he anticipated being able to play in Saturday's grand final.