ABSTRACT
The exterior enclosure is comprised of non-load bearing visible exterior. The enclosure, referred to as building envelop, is first line of defense against inclement weather, thermal discomfort, wind, and structural damage. As the first line of defense, exterior enclosure includes roof, walls, and windows and doors. Exterior wood window frames and doors are high maintenance, particularly in climates where there are temperature extremes. Non-waterproof adhesives used in exterior wood products will separate and interior wood products used outdoors may deteriorate. Interior hollow-core wood doors have occasionally been used as exterior doors. Interior hollow-core wood doors are typically made of thin panels of medium density fiberboard (MDF), also referred to as hardboard and chipboard. Metal window frames and doors are generally hollow core or core filled. Steel door thickness and steel stiffeners bestow security. Rigid vinyl window frames and doors were introduced in middle 1900s and became popular in the 1990s. High density fiberboard (HDF) is thermoset resin-impregnated, steam-exploded wood fibers.
