DENVER — "Of course it's frustrating, but that's how baseball goes," Pacheco said. "We've just got to keep swinging, keep getting guys on."
Tulowitzki homered in the ninth off reliever Jose Veras and off starter Erik Bedard in the fourth for his seventh career multihomer game. The last was Aug. 27, 2011, against the Los Angeles Dodgers.
The Rockies couldn't take advantage of a solid start from Tyler Chatwood, who struck out 10 batters in six innings.
"Tyler did a great job," Rockies manager Walt Weiss said. "We didn't get the big hit to get the big inning. But Tyler certainly did his part."
The strikeout total was the most in a game by a Rockies starter this season and a career high for Chatwood, who allowed two runs on four hits.
"I think I was getting ahead and I was able to put some guys away with my slider," Chatwood said. "Me and Jimmy (Wright, Rockies pitching coach) worked on it in our last side session. It's been kind of inconsistent, but I found it tonight."
Bedard also pitched well and did not get a decision. He went six innings and allowed two runs on seven hits. It was the third consecutive outing in which he has allowed only two runs.
Houston struck first, getting a run in the second inning on Matt Dominguez's sacrifice fly.
Tulowitzki answered leading off the fourth, when he drove the first offering from Bedard the opposite way into the right-field seats. It was his 11th home run of the season and also produced the 500th run scored of his career.
Tulowitzki's two-out double in the fifth drove in Pacheco. But the Astros tied it up at 2-all in the sixth when Barnes scored on a sacrifice fly by Castro.