Sales of newly built, single-family homes in January moved 19% higher than a year ago, as home buyers sought more options under a lean number of existing homes for sale.

Newly built single-family home sales increased 4.3% last month over December 2020, reaching a seasonally adjusted annual rate of 923,000, the U.S. Department of Housing and Urban Development and U.S. Census Bureau reported Wednesday.

“Historically low mortgage rates and solid demand spurred an increase in new home sales in January,” says Chuck Fowke, chairman of the National Association of Home Builders. “However, rising affordability issues are looming this year, particularly increasing building material costs, including lumber, which is adding $24,000 to the price of a typical newly built home. Builders also cite rising regulatory issues as a potential concern.”

As existing-home inventory remains at all-time lows, more buyers are considering new home construction, says Robert Dietz, chief economist of the National Association of Home Builders. “Though rising building and development costs, combined with recent increases in mortgage interest rates, threaten to exacerbate existing affordability conditions,” he says. “Builders are exercising discipline to ensure home prices do not outpace buyer budgets.”

Inventories of new homes also remain tight at just a four-month supply at the current sales pace. New-home inventories are 6.3% lower than January 2020.

The median sales price for a new home was $346,400 in January, up 5.3% from a year earlier.

New-home sales rose by the highest amounts in the Midwest last month, up 12.6% annually. New-home sales also posted a 6.8% increase in the West and a 3% increase in the South. The only region of the U.S. to post a decline in new home sales in January was the Northeast, where new home sales fell 13.9% annually.