4.1 Overview

The objective of the Building Energy Efficiency Standards (Energy Standards) for mechanical systems is to reduce energy consumption while maintaining occupant comfort by:

1. Maximizing equipment efficiency at design conditions and during part load operation

2. Minimizing distribution losses of heating and cooling energy

3. Optimizing system control to minimize unnecessary operation and simultaneous use of heating and cooling energy

An important function of the Energy Standards is indoor air quality for occupant comfort and health. The 2019 Standards incorporate requirements for outdoor air ventilation that must be met during normally occupied hours.

This chapter summarizes the requirements for space conditioning, ventilation, and service water heating systems for non-process loads in nonresidential buildings. Chapter 10 covers process loads in nonresidential buildings and spaces.

This chapter is organized as follows:

Section 4.1 overview of the chapter and the scope of the mechanical systems requirement in the Energy Standards

Section 4.2 requirements for heating, ventilation, and air conditioning (HVAC) and service water heating equipment efficiency and equipment mounted controls

Section 4.3 mechanical ventilation, natural ventilation, and demand controlled ventilation

Section 4.4 construction and insulation of ducts and pipes and duct sealing to reduce leakage

Section 4.5 control requirements for HVAC systems including zone controls and controls to limit reheating and recooling

Section 4.6 remaining requirements for HVAC systems, including sizing and equipment selection, load calculations, economizers, electric resistance heating limitation, limitation on air-cooled chillers, fan power consumption, and fan and pump flow controls

Section 4.7 remaining requirements for service water heating

Section 4.8 performance method of compliance

Section 4.9 compliance requirements for additions and alterations.

Section 4.10 glossary, reference, and definitions.

Section 4.11 mechanical plan check documents, including information that must be provided in the building plans and specifications to show compliance with the Energy Standards

Acceptance requirements apply to all covered systems regardless of whether the prescriptive or performance compliance approach is used.

Chapter 12 lays out the mandated acceptance test requirements, which are summarized at the end of each section.

The full acceptance requirements are in §120.5 of the Energy Standards and in the 2019 Reference Appendix NA7.

4.1.1          What’s New for 2019

      Demand response HVAC controls

Open ADR 2.0

Occupancy sensors

      Air filtration requirements


Pressure Drop


      Ventilation and indoor air quality

Kitchen range hoods

Natural ventilation criteria

Minimum ventilation rates

Exhaust ventilation

Zone air distribution effectiveness

Air classification and recirculation limits

      Demand control ventilation updates

      Healthcare facilities

      Fan power limitation changes

Pressure drop adjustment

      Variable air volume zone controls

      Passive waterside economizer requirements

Integrated waterside economizer

      Cooling tower efficiency

      Exhaust system transfer air

      Expanded economizer fault detection diagnostics

      Adiabatic condenser requirements

4.1.2          HVAC Energy Use

Mechanical and lighting systems are the largest consumers of energy in nonresidential buildings. The amount of energy consumed by various mechanical components varies according to system design and climate. Fans and cooling equipment are the largest components of energy consumed for HVAC purposes in most building in lower elevation climates. Energy consumed for heating is usually less than fans and cooling, followed by service water heating.

Figure 4-1: Typical Nonresidential Building Electricity Use


Heating, cooling and ventilation account for about 28 percent of commercial building electricity use in California.


Source IEQ RFP, December 2002, California Energy Commission No. 500-02-501.

4.1.3          Mandatory Measures

Mandatory measures, covered in §110.0-110.12 and §120.0-120.9, apply to all nonresidential buildings, whether the designer chooses the prescriptive or performance approach for compliance. The following sections are applicable to mechanical systems:

1.   Equipment certification and equipment efficiency - §110.1 and §110.2

2.   Service water heating systems and equipment - §110.3

3.   Pool and spa heating systems and equipment - §110.4

4.   Restrictions on pilot lights for natural gas appliances and equipment - §110.5

5.   Demand responsive controls - §110.12

6.   Ventilation and indoor air quality requirements - §120.1

7.   Control requirements - §120.2

8.   Pipe insulation - §120.3

9.   Duct construction and insulation - §120.4

10.  Acceptance tests in §120.5 and the 2019 Reference Appendices NA7

11.  Commissioning - §120.8

12.  Commercial Boilers - §120.9

4.1.4          Prescriptive and Performance Compliance Approaches

The Energy Standards allow mechanical system compliance to be demonstrated by meeting the mandatory requirements and the requirements of either the prescriptive or performance compliance approaches.      Prescriptive Compliance Approach

The measures in the prescriptive compliance approach, §140.4, cover specific requirements for individual components and systems that directly comply with the Energy Standards, including:

1.  §140.4(a) and (b) -Load calculations, sizing, system type and equipment selection

2.  §140.4(c) - Fan power consumption

3.  §140.4(d) - Controls to reduce reheating, recooling and mixing of conditioned air streams

4.  §140.4(e) - Economizers

5.  §140.4(f) - Supply temperature reset

6.  §140.4(g) - Restrictions on electric-resistance heating

7.  §140.4(h) - Fan speed controls for heat rejection equipment

8.  §140.4(h) - Limitation on centrifugal fan cooling towers

9.  §140.4(i) - Minimum chiller efficiency

10.  §140.4(j) - Limitation on air-cooled chillers

11.  §140.4(k) - Hydronic system design

12.  §140.4(l) - Duct sealing

13.  §140.4(m) - Supply fan control

14.  §140.4(n) - Mechanical system shut-off control

15.  §140.4(o) - Exhaust system transfer air      Performance Compliance Approach

The performance compliance approach, §140.1, allows the designer to trade off energy use between different building systems. This approach provides greater design flexibility, but requires extra effort and a computer simulation of the building. The design must still meet all mandatory requirements.

1.  Performance approach trade-offs can be applied to the following disciplines: mechanical, lighting, envelope, and covered processes. The performance approach requires creating a proposed energy model using approved Energy Commission compliance software. The software will automatically create a standard design model based on the features of the proposed model and compare the energy use of the two: Standard design energy model that meets mandatory and prescriptive requirements (per the Alternative Calculation Method Reference Manual).

2.  Proposed design energy model that reflects the feature of the proposed building.

The proposed model complies if it results in lower time dependent valuation (TDV) energy use than the standard design model.

The performance approach may only be used to model the performance of mechanical systems that are covered under the building permit application (see Section 4.8 and Chapter 11 for more detail).