## 5.1 Overview

Chapter 5 describes the compliance requirements for domestic water heating for residential dwellings, including single-family, and low-rise (three or fewer habitable floors) multifamily buildings with a dedicated water heater for each dwelling unit or a central system that serves multiple dwellings. This chapter also describes common water heater types, best practices for water heater maintenance, hot water distribution system designs, and examples of commonly asked questions regarding compliance with Energy Standards requirements. For general information about compliance and enforcement please see Chapter 2 of this compliance manual.

### 5.1.1 What’s New for 2016

This section summarizes changes to the requirements for residential water heating for the 2016 Energy Standards. Please see Section 5.3 and 5.4 for detailed information on the mandatory and prescriptive water heating requirements in the 2016 Energy Standards.

5.1.1.1 Mandatory Requirements

1. Isolation valves must be installed on instantaneous water heaters that have an input rating greater than 6.8 kBTU per hour (2 kilowatts [kW]). The valves must be installed on the cold water line leading to the water heater and the hot water line leaving the water heater. As discussed in Section 5.2.3 of this chapter, manufacturers recommend flushing the heat exchanger in instantaneous water heaters. Isolation valves simplify this routine maintenance practice, which reduces the cost and burden of maintaining the water heater.

2. Storage water heaters do not need to have blankets anymore. The 2013 Energy Standards required storage water heaters with efficiency levels equivalent to the minimum federal efficiency standard to be externally wrapped (such as with a water heater blanket) with insulation of R-12 or greater. This requirement has been deleted. With the amended federal standards that went effect on April 16, 2015, external insulation of water heater storage tanks is no longer cost-effective.

3. For alterations, all newly installed hot water piping and existing accessible piping must be insulated if installing new piping at the time an existing water heater is replaced (that is, replacement water heating systems).

5.1.1.2 Prescriptive Requirements

The prescriptive requirements for new construction and additions for single-family buildings and multifamily buildings with a dedicated water heater for each dwelling unit have been updated. A dwelling unit is defined as a residence with a dedicated water heater. Use of the term pertains to both a single-family home and a unit (such as an apartment) within a multifamily building that has a dedicated water heater.

The 2016 prescriptive requirements for single-family buildings and multifamily buildings with a dedicated water heater in each dwelling unit are as follows:

Option 1: Install a natural gas or propane instantaneous water heater that meets the minimum requirements in California’s Title 20 Appliance Efficiency Regulations, Section 1605.1(f) for federally regulated appliances.

Option 2: Install a natural gas or propane storage water heater with a rated storage volume of 55 gallons or less that meets the minimum requirements in California’s Title 20 Appliance Efficiency Regulations, Section 1605.1(f) for federally regulated appliances. In addition, the building must comply with the HERS-verified Quality Insulation Installation (QII) requirements (see Chapter 3 of this compliance manual), as well as one of the following requirements:

1. HERS-verified pipe insulation (see Reference Appendix RA 3.6, RA4.4.1, RA4.4.3, and RA4.4.14 for the requirements of proper installation of pipe insulation and Section 5.6.2.5 of this chapter)

2. HERS-verified compact hot water distribution design (see Reference Appendix RA 3.6 and RA4.4.16 for requirements and Section 5.6.2.4 of this chapter)

Option 3: Install a natural gas or propane storage water heater with a rated storage volume more than 55 gallons and an input rating of 105,000 BTU/hr or less. The water heater must meet the requirements in California’s Title 20 Appliance Efficiency Regulations Section 1605.1(f) for federally regulated appliances. In addition, the building must comply with one of the following:

1. HERS-verified pipe insulation

2. HERS-verified compact hot water distribution design.

There is no longer a prescriptive option that allows electric water heating. Users that wish to use electric water heating can comply with the standards using the performance approach.

5.1.1.3 Performance Compliance Options

1. The water heating energy budget is now based on the energy performance of a natural gas instantaneous water heater that meets the minimum requirements in California’s Title 20 Appliance Efficiency Regulations Section 1605.1(f) for federally regulated appliances.

2. The point-of-use distribution credit no longer requires HERS verification.

### 5.1.2 At a Glance

Table 5-1 provides an overview of the location of the water heating requirements in the 2016 Energy Standards by construction and building type.

#### Table 5-1 Overview of Water Heating Requirements in the Energy Standards and this Chapter

Type | Mandatory Requirements | Prescriptive Requirements | Performance Requirements
Standards Section | Manual Section | Standards Section | Manual Section | Standards Section | Manual Section
Single-family home – Newly built | §110.3; §150.0(n) | 5.3 | §150.1(c)8A i,ii,iii | 5.4.1 | §150.1(b) | 5.5
Single-family home – Addition | §110.3; §150.0(n) | 5.3 | §150.2(a)1D | 5.4.1 | §150.2(a)1D | 5.5
Single-family home – Alteration | §110.3; §150.0(n) | 5.3 | §150.2(b)1 | 5.4.1 | §150.2(b)1 | 5.5
Multi-family – Newly built individual dwelling units | §110.3; §150.0(n) | 5.3 | §150.1(c)8A | 5.4.2 | §150.1(b) | 5.5

### 5.1.3 Water Heating Energy

Water heating accounts for the largest share of natural gas usage (49 percent) in California homes. Nearly 90 percent of California homes have natural gas water heating, with the common water heater type being a 40- or 50-gallon atmospheric combustion storage water heater. Standby loss associated with the center flue design represents about 25-35 percent of the annual energy use of a typical gas storage water heater system. Roughly 6 percent of households use electricity to heat water, and most of the remaining homes use propane (liquefied petroleum gas or LPG).

Total energy use associated with water heating consists of the end use, heater inefficiencies, standby loss, and distribution system inefficiencies. Figure 5-1 below shows the energy flows that constitute water heating energy usage. Hot water draws at the end use points (for example, faucets, showers, and so forth) represent the useful energy consumed. In most cases, hot water that is actually used represents the largest fraction of water heating energy use, although in situations when there are very few hot water draws, standby losses from the water heater and the hot water distribution system can exceed the quantity of useful energy consumed at the end point. Energy impacts associated with the hot water distribution system vary widely based on the type of system, quality of insulation and installation, building and plumbing design, and hot water use patterns. Distribution losses in a typical single-family home may be as much as 30 percent of the total energy used for water heating. Distribution losses in single-family homes with compact hot water distribution systems may be lower than 10 percent of total water heating energy use. In a typical multifamily building, distribution losses can account for more than 30 percent of total water heating energy use. An important consideration for any water heating system is the recovery load (that is, end use plus distribution losses) of the water heating unit minus any contribution from auxiliary heat inputs, such as a solar thermal system.

#### Figure 5-1 – Water Heating Energy Flow Representation