After starting the season 0-3 with a 10.57 ERA in his first four starts of the season, Redding (3-3) is 3-0 with a 1.73 ERA in his five starts since.
The Astros jumped out to an early lead against Cardinals' starter Matt Morris (4-5) as Jeff Kent singled home Adam Everett in the first. Kent's hit pushed his hitting streak to a career-high 15 games.
Lamb stretched the lead to 3-0 with his two-run homer in the fourth inning.
Morris kept the game close giving up three runs in seven innings, and did not surrender a hit after the fourth inning.
Houston broke open the game in the eighth inning, scoring four runs on two-run homers by Jeff Bagwell and Lance Berkman.