## 3.1 Chapter Overview

This chapter covers the requirements for efficiency measures used for the building envelope of nonresidential, high-rise residential, hotel and motel occupancy buildings. Building energy use is affected by heating and cooling loads.

• Heating loads are affected by infiltration and conduction losses through building envelope components, including walls, roofs, floors, slabs, windows, and doors.

• Cooling loads are dominated by solar gains through windows and skylights, internal gains due to lighting, plug loads, and occupant use, and from additional ventilation loads needed for indoor air quality.

### 3.1.1 What’s New for 2019

The 2019 Building Energy Efficiency Standards (Energy Standards) include two important changes to the building envelope component requirements as described below:

• The site-built fenestration requirement is reduced from a 1,000 square feet to 200 square feet (NA6).

• Daylighting design power adjustment factors (PAFs) are available for the following daylighting devices: clerestory fenestration, interior and exterior horizontal slats, and interior and exterior light shelves.