Chavez didn't need the 18 months authorization to rule dy decree (which by the way was given to him by a Parliament which had only a WEEK of mandate left) for this housing program. He just needed the 50% majority, which he already had*. So the opposition could NOT block this program in any manner.
The housing program, by the way, is largely insufficient and superficial. Its numbers are fake too, since the government chose to include houses built by the private sector!. Chavez promised that the government would build 150,000 homes for 2011 and, finally, they only built around 90,000. So now, they're trying hard to disguise that well-known and admitted fact through the diffusion of this kind of fake news. Most notably in venezuelanalysis, which is a structure created by the Venezuelan consulate in the US. You want to applaud for this type of failure in our social policies, I believe it's a shame: with a barrel of oil topping the 100$ line, the richest government in Venezuelan history is only able to keep 60% of its promise when it declares itself "socialist". Moreover, they're forced to cheat the numbers and try to diffuse the message through their own informative structures to hide their failure.
*The authorization to rule by decree empowers you to act as if you had a 60% qualified majority. It's only useful if you want to change the Constitution. Which they did. Among other things, they immediately voted a law that forbids to a deputy to vote against his party. They wouldn't have been able to do it without the rule by decree authorization because it was uncostitutional.