In hopes of solving what he has called "a crisis in housing," Boston Mayor Thomas M. Menino announced Monday that a percentage of all Boston luxury developments will now be required to go toward constructing affordable housing.

The executive order stipulates that developers either set aside 10 percent of their developed units at affordable prices or else construct off-site housing units equal to 15 percent of their development.

While the move has been lauded by members of the Boston Department of Neighborhood Development, others have worried that the move might have a stifling effect the Boston development market.

But according to Edwin J. Shanahan, the CEO of the Greater Boston Real Estate Board, a conglomeration of real estate professionals, the mayor's order will only be one factor and will not slow building.

"There are other obstacles to production such as land costs and construction costs. The developers who can afford these will be able to fulfill the mayor's order," Shanahan said.

Since the new initiative is an executive order rather than a change to zoning laws, Shanahan said, the mayor will be easily able to adapt the arrangement if a downturn in the economy threatens development in the future.

Menino's order comes amidst mounting concern among some city residents that Boston is losing affordable housing at an alarming rate.

A Harvard report released in November found that the price of housing in Boston has risen more than 200 percent since 1980. The change has been blamed both on the booming economy and the abolition of rent control.