As consequence of the win, Houston move up to seventh in the Eastern Conference standings and two points behind Union, who occupy the fifth and final playoff spot.
The hosts enjoyed plenty of possession throughout the first half but struggled to make their dominance count. Jim Curtin's side had no such worries early in the second half, however, as Dynamo edged ahead on 51 minutes.
Captain Brad Davis galloped down the left-hand flank before squaring to the unmarked Bruin, who tapped home from close range to send the Texans into a one-goal lead.
Curtin's troops sealed the win in the closing stages when Omar Cummings's cross was diverted past goalkeeper Andre Blake by Gaddis to kill off any hopes of a Philadelphia comeback.