There are many categories of exterior construction and building materials and numerous sources of natural and man-made or synthetic products that comprise these categories.  Buildings and their construction count for nearly half of all greenhouse gas emissions and energy consumed in the U.S. each year. There is a great deal of environmental concern related to construction and building materials.  These concerns relate to issues such as the future availability of natural resources, the sustainability of certain materials, and the impact the production and use of some types of material have on the environment.  There is a current trend to utilize exterior building materials that are environmentally friendly, sustainable, and efficient.  Providers listed in this section are committed to offering environmentally friendly exterior building materials, resources and products, whenever possible.