Richard Wood opened the scoring after six minutes when he was decisive amid a goalmouth scramble to put the ball over the line.
Jermaine Johnson doubled the hosts' lead six minutes later when Luke Varney charged past two defenders and into the box before squaring the ball for his team-mate to hit the ball in via a deflection.
The game was all but over after just 34 minutes when Marcus Tudgay headed home as the Owls dominated proceedings against a lacklustre Scunthorpe side.
The Owls continued to put the pressure on in the second half and made it 4-0 after 58 minutes when Darren Potter slammed a spectacular half-volley in from the edge of the area.
Varney could have had a debut goal after six minutes when he closed in goal but his shot was pushed around the post by Joe Murphy.
From the resulting corner Wednesday took the lead when Darren Potter's deep corner was headed back across goal by Tommy Spurr and bundled over the line by Wood.
The Owls doubled their advantage after 12 minutes when Johnson grabbed his fourth of the season after great work by Varney on the right.
Scunthorpe looked like they were struggling to keep up with the tempo the hosts had set in the early stages but did manage a shot through Paul Hayes which was blocked by Darren Purse.
The visitors lost centre-half Rob Jones after 28 minutes when he clashed with Luke Varney in the box and suffered a nasty gash on his head and was replaced by Niall Canavan.
The Owls continued to boss the game and it was no surprise to see them add a third goal when Marcus Tudgay headed home a Michael Gray corner to all but seal victory with over 10 minutes left of the first half.
The second half continued in much the same fashion, as the home side kept the pressure up and Varney continued to look likely to make something from nothing.
Murphy made a fine save from the loanee when he was clear through and it looked like he would grab a deserved goal.
The Wednesday fans were not waiting for long until they grabbed a fourth when a corner from Gray was cleared only as far as Tudgay on the edge of the area. He laid the ball off to Potter who smashed the ball on the half-volley high into the top of the net.
Scunthorpe failed to create a chance as the clock ticked down and the hosts completed a comfortable first win of the season.