This course examines how environmental forces acting on building envelope components and building systems guide decision-making in building design. Building science theory and principles are applied to the control of heat, air and moisture flows across building envelope systems and to the design of a range of building envelope systems. Analytical techniques are used to assess the suitability of examples of building conditions. Life safety driven separator issues are addressed in reference to the Ontario Building Code. Related issues are reviewed within the context of existing and emerging building technology.