Prescriptive Compliance

As stated earlier, the 2019 California Energy Code outlines two primary methods of compliance: Prescriptive and Performance. The Prescriptive Method requires that each element of a building be analyzed individually and meet the minimum requirements described for each. For building envelopes, this typically, this can be completed by using code prescribed charts and tables that outline minimum U-values for walls, windows, roofs, etc and configuring these system to meet this minimum.

The prescriptive approach is the simpler way to comply with the Standards. Each of the three major energy related building systems must comply independently from the others. If the design fails to meet even one of the requirements, then the system does not comply with the Standards. The performance approach provides the most flexibility to the building designer for choosing alternative energy efficiency features.

Building Envelope. The prescriptive envelope requirements are determined assessing each major component of the Building envelope: the roof, opaque walls and fenestrations (doors and windows). This approach is described in detail in Chapter 3 of the compliance manual. The stringency of the envelope requirements varies according to climate zone and occupancy type. Each element in the envelope must the prescriptive requirements defined for each wall type.

Nonresidential, High-rise Residential and Hotel/Motel Buildings

Exterior walls can meet prescriptive requirements based on the construction the wall assembly. The wall assembly must have a U-factor lower than the specified criteria. There are five different general wall system types as shown below (from Compliance Manual). A summary table from the compliance manual for maximum values for U-factors for opaque wall for different climate zones and wall types are shown in the table shown below.

Table 3-8: Wall U-Factor Requirements

The linked example illustrates how an exterior masonry wall system can be designed prescriptively for a non-residential application.

CMU Fully Grouted Wall Prescriptive Examples
CMU Fully Grouted Wall Design Example and Guidance

TASK: Design an 8-inch CMU wall following the Prescriptive Method and show various wall configurations acceptable for Climate Zone 8 and/or Climate Zone 16 outlined in the 2019 California Energy Code.

This document also completes a design for for a 12-inch CMU wall.

Next: Building Performance Compliance