On Friday, Nicole Scope, project manager, is overseeing the installation of the “green roof” at the East Village Green Townhouse.   Now that spring is here, it will be pleasant to lounge on the roof, among the multicolored sedum plants and under the shade of hanging vines.  The construction of a green roof is complicated, and NMA has walked the clients through each of the stages, from discussing the structural load requirements for a green roof and roof membranes, to arranging the color of the sedum and finding the right seasonal plants.  The attention to detail is worth it, though — green roofs come with  substantial energy savings, as they trap heat in the winter and diffuse the sun in the summer.