The Rockets led by only five heading into the fourth quarter, but pulled away in the closing 12 minutes to cool off the Suns. Phoenix has lost two straight after winning seven out of nine.
Howard made 11-of-17 from the field and was backed up by James Harden with 23 points. In two games since returning from a thumb injury, Harden has scored 51 points.
Houston hit 54 percent of its field goal tries and went 11-of-16 from beyond the 3-point arc.
Goran Dragic scored 23 points for the Suns.