(2012 Denver Broncos season)The Texans entered this highly anticipated early season matchup coming face-to-face once again with a familiar longtime AFC South nemesis in the form of former Colts quarterback Peyton Manning, who had sat out the 2011 season due to a neck injury.  Now back and in Denver, Manning came into the game looking to continue his mastery over the Houston Texans franchise.  However, it was Matt Schaub who took control of the game early, throwing 4 touchdown passes, and overcoming a brutal hit where he lost a chunk of his ear.  Despite Peyton Manning fueling a Broncos comeback attempt in the 4th quarter, the Texans were able to hang on and defeat the Broncos by 6 points.  With the win, the Texans improved to 3-0 for the first time ever. This was also their first road victory against Peyton Manning as they improved to 1-0 against Peyton in road games as a Bronco (0-9 vs. Peyton on the road as a Colt). The Broncos sacked Matt Schaub on the 2nd drive of the game making it 2-0. The Broncos drove 48 yards and kicked a 32-yard field goal from Matt Prater to make it 5-0. On the next drive, Schaub threw a 60-yard touchdown pass to Andre Johnson to make it 7-5. On their next drive, Houston went on a 98-yard drive resulting in a 3-yard touchdown pass from Schaub to Arian Foster making it 14-5. After a 3-and-out by Denver, Schaub threw a 52-yard touchdown pass to Kevin Walters to make it 21-5. Denver scored a field goal by Prater to make it 21-8. Denver would get another field goal before the half ended to make it 21-11. To open the second half Houston scored to make it 24-11. Then Schaub threw to Owen Daniels to make it 31-11. But after a Houston fumble, Denver scored its first touchdown of the night to cut it to 31-18. After a punt, Denver scored again to make it 31-25. However Houston stopped a desperation lateral play to win 31-25 and improve to 3-0. Schaub threw for 4 touchdowns and played his best game of the season up to that point.
Question: How many points did Houston score in the first half?
Answer: 21