HOUSTON -- Many times this season when J.A. Happ got into trouble on the mound, the left-hander was unable to make the pitches necessary to escape those jams.
That wasn't the case Thursday night.
The shutout wrapped up a two-game sweep for the Astros, who took the opener 8-3.
Happ (3-3) yielded seven hits and walked one, managing to escape jam after jam as the Brewers stranded eight while he was on the mound.
"He had to work out of some jams and he got some pretty good hitters to work out of those jams," Houston manager Brad Mills said. "He had to make those pitches to get out of it, but we've seen the last couple outings that it's been kind of tough to make those pitches, and tonight he was able to make the pitches. It was sure great to see."
Chris Snyder, batting .179 this season, had two hits -- including an RBI single after Lowrie's homer in Houston's four-run fourth. Jordan Schafer drove in a run later in that inning with a single and also had a double in the third.
Milwaukee starter Shaun Marcum (2-2) allowed four runs -- three earned -- and a season-high nine hits in five innings. The Brewers said he was bothered by a cramp in his oblique before the game, but he didn't feel it again after warming up.
Marcum called the team's 1-3 road trip to New York and Houston "terrible."
"We're getting guys on base. We just have to get hits with guys on base, and pitchers have to make pitches when they have runners on base and play good defense," Marcum said. "Just do all the things you were taught as a little kid, you know? Play the game fundamentally sound, and if we do that, hopefully things take care of themselves."
Lopez allowed his first walk of the season to Aramis Ramirez in the eighth inning. Before that he had faced 78 batters without a walk, which was the longest such streak by a reliever to start a season since John Smoltz went 92 hitters before walking one in 2004.
"The ball bounced our way tonight. Sometimes it doesn't, and that's kind of the difference," Happ said. "We were fortunate for that and we played good defense."
Happ walked Marcum with one out in the third before a double by Norichika Aoki. Rickie Weeks followed with an infield single -- his second hit in his past 29 at-bats -- but Happ retired Ryan Braun and Ramirez to pitch out of the bases-loaded jam.
Happ got into trouble again in the fifth after a single by Cesar Izturis before a one-out single by Aoki. An error by right fielder Brian Bogusevic allowed Aoki to advance to second and Izturis to move to third. Happ got out of this one by striking out Weeks before a groundout by Braun.
In what became a theme for his night, Happ got into another jam in the sixth. A double by Corey Hart before a single by Jonathan Lucroy left runners at the corners with one out. Happ escaped unscathed yet again when Snyder caught a foul popup by Brooks Conrad and Izturis grounded into a force out to end the inning.
"We have a lot of things that we have to start doing better offensively," Milwaukee manager Ron Roenicke said. "Regardless of what happened in the fourth inning with Marcum, we don't score, and we need to start scoring."
The performance helped Happ put his past two starts, when he allowed 11 runs combined, behind him.
"I didn't want to put too much pressure on myself, but I definitely wanted to go out and have a good one," Happ said. "I felt good physically and mechanically and ... I wasn't overthrowing."
Carlos Lee singled in the fourth before Lowrie's shot to right field, which sailed over the outstretched arm of a leaping Hart, put Houston up 2-0. Bogusevic singled before scoring on a one-out single by Snyder.
Snyder advanced to second on the play thanks to an error by Aoki in center field. Schafer capped the scoring with a two-out RBI single.
Brewers SS Alex Gonzalez had surgery on the anterior cruciate ligament in his right knee in Milwaukee. His recovery time is expected to be six months. ... Roenicke expects OF Carlos Gomez (strained left hamstring) to be activated from the disabled list on Sunday. He is on a rehabilitation assignment with Class-A Wisconsin. ... Houston opens a three-game series with the Rangers on Friday, with Wandy Rodriguez facing Texas right-hander Neftali Feliz. ... Brewers RHP Marco Estrada opposes Minnesota left-hander Scott Diamond in the opener of a three-game set Friday.