CITY OF NEWBURGH — Old Rockefeller Center Christmas trees never really die, they just get built into the wall frames and floor supports of affordable homes. For the past decade, the ornament-laden trees that have been lit up with glitz, songs and dancing Rockettes have gone on to be milled into lumber used in dozens of Habitat for Humanity homes from Philadelphia to Pascagoula, Mississippi. Each tree yields a truckload of 100 or more boards, all stamped with an image of the tree and the year it was on display. …The Rockefeller wood is more symbolic than structural. That’s because the big Norway spruces that tower over skaters each December at Rockefeller Center are show trees, not work trees, with wood often too knotty to support a lot of weight.