Davis converted a pass from Kofi Sarkodie with a crossing shot that found the far side of the net for the Dynamo, who broke Real Salt Lake's previous MLS record for most consecutive home games without a loss.
Will Bruin marked his return from an injury with a first-half goal for Houston (4-2-0), which vaulted over idle Sporting Kansas City into a first-place tie with Montreal atop the Eastern Conference.
Chris Rolfe scored for the Fire (1-4-1).
Notable deaths of 2014 [PHOTOS]
Arizona Cardinals player formally charged