It was an encouraging defensive display from the Owls in Jos Luhukay's first game as manager, but a missed opportunity for the Blades who have now won just one of their last 10.
Luhukay set up Wednesday with a new-look back-three formation at Bramall Lane, and the Owls were extremely well organised to restrict United's chances in the first half.
Wednesday posed little more of an attacking threat, but did create a few half-chances as they grew into the game after withstanding the initial Blades assault.
This was the first Championship match of the season in which there were no shots on target in the first half as it took until the 51st minute for a goalkeeper to be worked, with Joe Wildsmith acrobatically tipping over the crossbar from Clayton Donaldson's flicked header.
Defender Daniel Pudil appeared Wednesday's most likely scorer as he twice let fly from range. Neither effort troubled Simon Moore, although a skilful volley had the United stopper scrambling across his goal as it came within inches of swerving into the bottom corner.
Loovens threatened to undo all of his side's good work with a booking in each half for clumsy and needless tackles on Donaldson, the second of which left the visitors with half an hour to play a man down.
United enjoyed a sustained period of pressure and passed up their best chances when Leon Clarke headed wide from Duffy's free-kick delivery, and John Fleck shot straight at Wildsmith from a well-worked corner.
However, it was Wednesday who came the closest to snatching a winner as Moore pushed an Adam Reach volley over, mere seconds after being left clutching his back following a collision with Richard Stearman.
The point takes the Blades into the playoffs, above Leeds United on goals scored, but it is a much better result for 10-man Wednesday and their new manager.
SHEFF UNITED (3-5-2): Moore; Baldock, Basham, Stearman; O'Connell, Stevens, Fleck, Lundstram, Duffy; Clarke, Donaldson (Wilson, 66')
SHEFF WED (3-5-2): Wildsmith; Venancio, Loovens, Pudil; Palmer, Jones, Wallace (Clare, 90'), Reach, Fox; Joao (Nuhiu, 82'), Rhodes (Boyd, 70')