3.      Building Envelope    

This chapter describes the requirements for efficiency measures used for the building envelope of nonresidential, high-rise residential and hotel/motel occupancy buildings. Building energy use is affected by heating and cooling loads.  Heating and cooling loads reflect the amount of energy needed, such as HVAC equipment size (capacity), to provide sufficient heating and cooling to meet inside temperature setpoints.  The principal elements affecting heating loads are infiltration through the building and conduction losses through building envelope components, including walls, roofs, floors, slabs, windows and doors. Cooling loads, however, are dominated by solar gains through windows and skylights, from internal gains due to lighting, plug loads, and occupancy use, and from additional ventilation loads needed for indoor air quality. For example, light entering the building through windows and skylights for daylighting purposes can add to the internal gains incurred by indoor lighting specified for various occupancy uses if both are not properly controlled.

Outside air ventilation and lighting loads are addressed in the Mechanical Systems and Lighting Systems chapters.

The design of the building envelope is usually the responsibility of the architect, but the design team may receive significant input from the contractor, engineer, or other design professionals. The designer is responsible for making sure that the building envelope complies with the standards. 'In 'addition, the building official is responsible for making sure that the building envelope is designed and built in conformance with the standards and that design measures shown on construction documents to meet energy requirements are installed properly. This chapter is written for the designer and the building official, as well as other specialists who participate in the design and construction of the building envelope.