ABSTRACT
This chapter provides information on minimum, good practice and advanced thermal standards for windows and external doors. Protection from falling through new windows and external doors is covered, including the need for safety glazing in critical locations, and cleanability. Guidance is included about how to install a roof window within the roof structure, as well as the use of sun pipes where borrowed light is needed. The Building Regulations limit the area of windows, roof windows and external doors in an extension to not more than 25% of the floor area of the extension plus the area of any windows or doors which, as a result of the works, either no longer exist or are no longer exposed. When installing a roof window, it is important to consider air leakage. These features reduce the risk of interstitial condensation by closing the air gaps between the frame of the roof window and the roof structure.
