It was a tight start to the match as Philadelphia were tired from their exertions on Tuesday as they qualified for the cup final, leading to a largely reserve squad on their weekend match.
After a first half-hour with few chances Houston started to go for the match and the team started to pass the ball around which saw Ricardo Clark get space at the top of the area, only to be denied by an Andre Blake save, his first big save in his MLS career.
One of the stars of that US Open Cup run had Philadelphia's first chance as a counter allowed Sebastian Le Toux to get a shot away which was well saved by Tally Hall.
In the 36th minute Le Toux had another fantastic opportunity, set up by former Dynamo man Danny Cruz, as the initial shot deflected off Kofi Sarkodie and fell to Le Toux but he couldn't find the target, which was the last clear action of the first half.
Houston were looking a better side than in previous weeks but just could not link up midfield with attack which limited their opportunities.
But after half-time Houston came out and went on the attack and six minutes in they had the opening goal after Will Bruin continued a run, when he released Giles Barnes. Barnes' shot did not result in a goal, but the ball came back out to Brad Davis, who returned it to Barnes, allowing him to send a ball across the face of goal which saw Bruin beat Blake to send the ball home.
With the Union tired from midweek the second half was all Houston as they attacked the Philadelphia goal almost constantly throughout the half and could well have doubled their lead in the 62nd minute.
A cross allowed Bruin to get free and beat his man but he wasn't able to put his chance away as his header was well saved well by Blake.
Union very nearly did find an equalizer, despite being exhausted debutant Pedro Ribeiro had two chances with eight minutes to play but saw his first saved by hall and the rebound blocked by David Horst.
Late in the match the 2-0 win was sealed by Houston after a pass from Omar Cummings was sent in to his own net by Raymon Gaddis, giving Houston the win.