U.S. Federal Reserve (Fed) Chairman Ben Bernanke on Thursday said that although the central bank managed to bring down the long-term interest rates through unconventional bond-buying programs, the U.S. housing sector has not got back on solid ground due to several headwinds.

Since the onset of the financial crisis, the Fed has rolled out two rounds of bond-buying programs, known as quantitative easing ( QE), to lower long-term interest rates and boost the market confidence, the economics professor turned Fed chief told George Washington University undergraduates during the last session of four lectures that he delivered this month.

The large inventory of vacant homes and more stringent lending requirements of banks have held back the recovery of the housing sector, Bernanke said.

The anemic housing sector recovery and declining home values helped cause the cautious attitudes of many consumers and the sluggish broader economic recovery, he added.

The lectures were not policy speeches, but offered insight into the Fed chairman's mindset on how to formulate the monetary policy. It was the Fed's latest effort to enhance its transparency of the decision-making process.