## 8.1 Overview

This chapter explains the performance method of complying with the 2016 Building Energy Efficiency Standards (Energy Standards). The method works by calculating the time-dependent valuation (TDV) energy use of the proposed design and comparing it to the TDV energy use of the standard design (the budget). The standard design is a building with the same surface areas as the proposed design but incorporates all the features of Prescriptive Package A. The energy budget includes water heating, space heating, space cooling, and indoor air quality (IAQ) fan energy. Lighting energy is not included in the performance calculations because all residential lighting measures are mandatory and therefore not eligible to be traded-off using the performance method. If the proposed design uses equal or less TDV energy than the standard design, then the building complies.

Computer programs used for compliance are approved by the Energy Commission as being capable of calculating space-conditioning and water-heating energy use in accordance with a detailed set of rules. The computer programs model the thermal behavior of buildings by calculating heat flows into and out of the various thermal zones of the building. The computer programs approved by the Energy Commission must demonstrate accuracy in analyzing annual space-conditioning and water heating energy use of different building conservation features, levels and techniques. This method provides maximum flexibility because the building designer may trade-off the energy performance of different building components and design features to achieve compliance. Making a building more efficient will result in lower utility bills and improved comfort. The performance approach provides the ability to test different options and choose the best strategy to reduce the overall energy budget. With today’s wide choice of high-efficiency materials, equipment, and controls, there are many opportunities to make a building more energy efficient. Improving the building envelope provides several opportunities for improving efficiency, in particular with measures related to window placement, location, and efficiency. In space-conditioning, there is not only equipment with very high efficiency for space heating and cooling, but many innovative system types that eliminate the need for ducts, combine space and water heating together, or use advanced designs that can dramatically improve the overall performance of the building. Improved water heating system efficiency includes a wide range of equipment that can significantly increase efficiency along with improvements to the distribution system design, which can drastically reduce energy losses.

The performance method is the most popular compliance method under the Energy Standards, with more than 95 percent of building permit applications for newly constructed buildings being submitted in this manner. The method is especially popular with production homebuilders because they can optimize performance and achieve compliance at a lower cost. This chapter provides a general overview of the performance method. Each computer program that is approved by the Energy Commission is required to have a compliance supplement that provides more detailed information regarding the use of the software for compliance purposes. The requirements for the compliance supplement along with other requirements for approved computer programs are documented in the 2016 Residential ACM Approval 'Manual.

For a detailed discussion of the performance method with additions and alterations, see Sections 9.5, 9.6 and 9.7..