Many materials can be considered a “green” material until its background is revealed. Any material that has used toxic or carcinogenic chemicals in its treatment or manufacturing (such as formaldehyde in glues used in woodworking), has traveled extensively from its source or manufacturer, or has been cultivated or harvested in an unsustainable manner might not be considered green. In order for any material to be considered green, it must be resource efficient, not compromise indoor air quality or water conservation, and be energy efficient (both in processing and when in use in the shelter).[1] Resource efficiency can be achieved by using as much recycled content, reusable or recyclable content, materials that employ recycled or recyclable packaging, locally available material, salvaged or remanufactured material, material that employs resource efficient manufacturing, and long-lasting material as possible.[28]