BOSTON - It took six days for builders to put together a modular classroom with wood panels and walls of windows on a concrete plaza in Boston this week.

But the temporary classroom — built in pieces at a factory, then transported and finished at the Boston Convention & Exhibition Center — has little in common with the aesthetically deadening modular buildings of lore. Its 40 windows direct sunlight inside at angles that keep the building cool in the summer and the heating system uses natural convection to keep people comfortable in winter.