Houston, which hadn't scored a goal in two games, scored four for the first time since defeating D.C. United 4-1 April 29, 2011.
"I'm really happy," Houston head coach Dominic Kinnear said. "Obviously, playing down a man is tough for any team, especially in this heat. I thought we managed the game well. It was a good night for us overall. It was something we needed to get on the scoreboard a lot -- 10 men or not. We had good chances in front of the goal, and the guys are feeling really good about the win."
Davis put the Dynamo (7-5-7, 28 points) ahead 1-0 in the 19th minute on a penalty kick that hit inside the far post. Houston earned the penalty after D.C. United goalkeeper Bill Hamid tripped Macoumba Kandji as he was going for a ball in the box. Hamid was given a red card on the play.
United's Branko Boskovic was replaced by backup goalkeeper Joe Willis after Hamid was ejected, and D.C. United (10-6-3, 33 points) played the final 71 minutes a man down.
"Bill is a young goalkeeper," United coach Ben Olsen said. "He is still going to have a game now and then when he doesn't make the right decision. I wasn't that pleased with our reaction."
Bruin put Houston up 2-0 in the 37th minute, getting a feed from Luiz Camargo from the right end line to the middle of the box and knocking it in an open net.
"We were playing against 10 men, but it was also important for us to put in the goals and not let them linger around," Bruin said. "That was huge for us to get an early one and not let them linger around. If we can get on them early, it makes this a very tough place to play."
Garcia made it 3-0 on a header from just outside the left 6-yard box and into the right net off a cross from Andre Hainault from the right sideline.
Ching converted another penalty kick in the 89th minute hitting the shot into the right net. Houston earned the penalty kick after Calen Carr was taken down by Danny Cruz in the box.
Davis nearly upped the lead to 2-0 in the 21st minute, but his shot from outside the upper box was batted up by Willis, off the bottom of the crossbar and cleared out of the box. Houston continued to pressure D.C. in the 23rd minute, with Bruin's header from 10 yards out in the middle box saved by Willis.
D.C. United's Robbie Russell was subbed out in the 40th minute because of plantar fasciitis in his left foot after getting tangled up with Kandji. Chris Kolb replaced Russell.
D.C. United lost for the second time in three games after a five-game winning streak. Houston outshot D.C. United 19-6, with Chris Pontius having D.C. United's best chances early on, having one shot miss wide right and another saved by Houston goalkeeper Tally Hall.