The average rate on a 30-year fixed mortgage reached a new low this week, falling to 3.88 percent, according to data released Thursday by Freddie Mac.

The average 30-year rate fell a fraction of a percentage point below last week’s 3.89 percent, the previous record low, and marks the seventh consecutive week in which the average has been below 4 percent. The average 15-year mortgage rate, which is popular among homeowners who are refinancing, hit 3.17 percent, up from last week’s 3.16 percent figure.

“Mortgage rates were nearly unchanged this holiday week in lieu of a mixed bag of economic data reports,” Frank Nothaft, vice president and chief economist at Freddie Mac, said in a statement.

He noted that retail sales rose only 0.1 percent in December but that the Reuters/University of Michigan consumer confidence index continued to climb in January to the highest reading since February 2011.

There have been encouraging signs of life in the housing industry in the past months as construction started to pick up, but sales volume and prices remain weak and many economists are forecasting little to no growth in the prices this year.

Data released Thursday showed the number of house-building permits issued reached an annualized rate of 679,000 in December, a 7.8 percent increase compared with December 2010. But the rate was essentially flat — down 0.1 percent — compared with November 2011. Last year was the worst year on record for new house construction.

“The report shows the housing industry is still in a holding pattern,” said Mitchell Hochberg of Madden Real Estate Ventures in New York. “The shadow inventory as a result of foreclosures needs to be resolved, and the jobless rate must drop considerably before the sector will see any constructive movement.”

A survey released Wednesday showed confidence among builders of single-family houses grew in January, the fourth consecutive month. The National Association of Home Builders/Wells Fargo builders sentiment index, which seeks their perceptions of sales and expectations for the next six months, rose four points to 25, the highest level since June 2007. The reading, however, is still below 50, indicating a negative sentiment.

The Washington-area housing market has fared better than many other parts of the nation, but recovery has been mixed. The median sales price fell 3.6 percent to $325,000 in December 2011, compared to the same period a year ago. Pockets of the region show strength, such as Fairfax and Loudoun counties in Northern Virginia along with sought-after neighborhoods in the District. But some areas in suburban Maryland, including parts of Montgomery County, are still struggling, and Prince George’s County leads the state in foreclosures; prices are still falling in parts of that county.

One big problem in the Washington market is the lack of inventory of houses for sale. There were 22 percent fewer houses for sale in December compared with the same period a year ago, according to RealEstate Business Intelligence, a division of the region’s local multiple listing service. That’s the lowest inventory the region has seen since 2005. There is some good news: locally, the number of homes in foreclosure has fallen, according to RBI.