Source: https://de.scribd.com/document/262997097/04-Building-HVAC-Requirements
Timestamp: 2020-08-12 13:03:19
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Matched Legal Cases: ['§110', '§110', '§110', '§110', '§110', '§110', '§150', '§110', '§150', '§150', '§110', '§110', '§150', '§150', '§120', '§150', '§110', '§110', '§110', '§110', '§150', '§150', '§150', '§150', '§150', '§150', '§150', '§151', '§150', '§150', '§150', '§150', '§150', '§150', '§150', '§150', '§150', '§150', '§150', '§150', '§150', '§150', '§150', '§150', '§150', '§150', '§150', '§150']

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4.1.1 Introduction and Organization
4.1.2 What’s New for the 2013 Standards
4.1.3 Common System Types
4.1.4 California Appliance Standards and Equipment Certification
4.1.5 Federal Appliance Standards (NAECA)
4.2 Heating Equipment
4.2.1 Mandatory Measures for Heating Equipment
4.2.2 Prescriptive Requirements for Heating Equipment
4.2.3 Compliance Options for Heating Equipment
4.3 Cooling Equipment
4.3.1 Mandatory Measures for Cooling Equipment
4.3.2 Prescriptive Requirements for Cooling Equipment
4.3.3 Performance Compliance Options for Cooling Equipment
4.4 Air Distribution System Ducts, Plenums, and Fans
4.4.1 Mandatory Measures for Air Distribution System Ducts, Plenums, and Fans
4.4.2 Prescriptive Requirements for Air Distribution System Ducts, Plenums, and Fans 41
4.4.3 Compliance Options for Air Distribution System Ducts, Plenums, and Fans
4.4.4 Duct Installation Standards
4.5.1 Thermostats
4.5.2 Zonal Control
4.6.1 Field Verification and Diagnostic Testing –
4.6.2 Typical Solutions for Whole-Building Ventilation
4.6.3 Whole-building Ventilation Flow Rate (Section 4 of ASHRAE 62.2)
4.6.4 Whole-Building Mechanical Ventilation Energy Consumption
4.6.5 Local Exhaust (Section 5 of ASHRAE 62.2)
Building HVAC Requirements Table of Contents
4.6.6 Other Requirements (Section 6 of ASHRAE 62.2)
4.6.7 Air Moving Equipment (Section 7 of ASHRAE 62.2)
4.6.8 Multifamily Buildings (Section 8 of ASHRAE 62.2)
4.7.4 Evaporative Cooling
4.7.5 Ground-Source Heat Pumps
4.7.6 Solar Space Heating
4.7.7 Wood Space Heating
4.7.8 Gas Appliances
4.7.9 Evaporatively Cooled Condensers
4.7.10 Ice Storage Air Conditioners
4.7.11 Non-Ducted Systems
4.7.12 Ventilation Cooling
4.8 Compliance and Enforcement
4.8.1 Design-Phase Documentation
4.8.2 Construction-Phase Documentation
4.8.3 Field Verification and/or Diagnostic Testing
4.9 Refrigerant Charge
4.9.1 Refrigerant Charge Verification
Building HVAC Requirements – Overview
This chapter addresses the requirements for heating, ventilating, and air conditioning (HVAC) systems. The requirements are presented in this chapter so that it may serve as a single source of information for mechanical system designers and mechanical system installers, as well as energy consultants, HERS raters and enforcement personnel.
Each section in this chapter outlines the mandatory measures and when applicable, the prescriptive requirements or compliance options. These prescriptive requirements vary by climate zone. When the building design does not achieve the minimum prescriptive requirements, then the compliance options may be used under the performance approach to achieve compliance.
The chapter is organized under the following sections:
8. Refrigerant Charge . More information on the refrigerant charge verification procedures is included in this section.
Chapter 9 covers the heating and cooling requirements for additions to existing dwellings and for alterations to existing heating and cooling systems.
The following is a summary of the new HVAC measures for the 2013 Standards, including new compliance options that provide greater flexibility in complying with the Standards when using the performance method. See individual sections of this Manual for more detail.
Mandatory Features and Devices - Section 150.0
7. The mandatory minimum duct insulation R-value has been raised from R-4.2 to R- 6, except for ducts located completely within directly conditioned space. [150.0(m)1]
9. There are some changes to the target leakage rates for dwellings in multi-family buildings. [150.0(m)11]
Prescriptive and Performance Compliance Approaches - Section150.1
1. When higher than minimum SEER ratings are specified using the performance approach, installation of proper equipment is now a HERS verified measure. Previously this only applied to high EER equipment. [150.1(b)4Bi]
2. There is now only one set of prescriptive measures (prescriptive package A). [150.1(c)]
3. There is a new allowance for supplemental heating systems. It includes limitations on size and requirements for timing controls. [150.1(c)6]
4. The temperature split approach to minimum airflow verification for refrigerant charge verification has been omitted. This reduces the number of required measurement access holes from two to one. [150.1(c)7Aia]
5. Some package units, mini-splits and variable refrigerant flow systems will be required to demonstrate proper refrigerant charge using a weigh-in approach and must be verified by a HERS rater. [150.1(c)7Aii]
6. Ducts not insulated because they are deemed to be in directly conditioned space must be verified by a HERS rater utilizing the duct leakage to outside procedures. [150.1(c)9]
7. There is a new prescriptive requirement in climate zones 8 through 14 for whole house fans designed to provide ventilation cooling. [150.1(c)12]
8. When homes utilizing the prescriptive approach have automatic zonal control, they are prohibited from using bypass ducts that divert supply air directly back to the return air stream. Using the performance approach, there is an energy penalty for systems choosing to utilize bypass ducts for zonal control. [150.1(c)13]
9. Maximum Rated Total Cooling Capacity compliance credit has been deleted.
Additions and Alterations - Section 150.2
The new requirements in the 2013 Standards for HVAC systems in homes that are altered or added to are summarized and discussed in Chapter 9.
The typical new California home in the central valley and the desert has a gas furnace and a split system air conditioner. Both heating and cooling is typically distributed to each of the rooms through air ducts. Most of the mandatory measures and prescriptive requirements are based on this type of system. In some areas, a heat pump provides both heating and cooling, eliminating the furnace. In coastal climates and in the mountains, air conditioning is rare and most new homes are heated by gas furnaces.
Although the Standards focus on the typical system, they also apply to other systems as well, including some radiant hydronic systems where hot water is distributed to parts of the home to provide at least some of the heat to conditioned space.
Electric resistance systems are used in some areas and applications, although it is difficult for them to comply under the Standards.
Ground-source or water source heat pump (geo-exchange) systems are also used, especially in areas where there is no gas service. Unlike the more typical air source
systems, these utilize water circulated underground or in large ponds or lakes as the heat source (in heating mode) and heat sink (in cooling mode).
This chapter focuses mostly on typical systems, but a section is provided to deal with the alternative systems as well.
§110.0 – General §110.1 – Appliance Efficiency Regulations
Most heating and cooling equipment installed in new California homes is regulated by the National Appliance Efficiency Conservation Act (NAECA) and/or the California Appliance Efficiency Regulations (Title 20). Both the federal and state appliance standards apply to the manufacture of new equipment and are applicable for equipment used in replacements, repairs or for any other purpose. The Appliance Efficiency Regulations are enforced at the point of sale, while the Energy Efficiency Standards explained this compliance manual are enforced by local enforcement agencies.
The following types of equipment (in the list below) are covered by the Appliance Efficiency Regulations. For this equipment, the manufacturer must certify that the equipment complies with the current Appliance Efficiency Regulations at the time of manufacture.
Appliances Covered by the Appliance Efficiency Regulations:
6. Gas-fired boilers
2. Room air conditioning heat
7. Gas-fired furnaces
8. Gas-fired floor furnaces
3. Central air conditioners with a
9. Gas-fired room heaters
cooling capacity of less than
10. Gas-fired duct furnaces
11. Gas-fired unit heaters
4. Central air conditioning heat pumps
5. Gas-fired central furnaces
The Appliance Efficiency Regulations do not require certification for:
1. Electric resistance space heaters
2. Oil-fired wall furnaces, floor furnaces, and room heaters (some are voluntarily listed with certified gas-fired furnaces).
Equipment that does not meet the Federal Appliance Efficiency Standards may not be sold in California. Any equipment covered by the Appliance Efficiency Regulations and sold in California must have the date of manufacture permanently displayed in an accessible place on that equipment. This date is frequently included as part of the serial number.
Note: Equipment manufactured before the effective date of a new standard may be sold and installed in California indefinitely, as long as the performance and prescriptive approach demonstrates energy compliance of the building using the lower efficiency of the relevant appliances.
The compliance and enforcement process should ensure that all installed HVAC equipment regulated by the Appliance Efficiency Regulations is certified to the Energy Commission.
Plan Review Process (Compliance)
During the plan review process builder must show compliance with the Appliance Efficiency Regulations by providing the efficiency of the HVAC equipment that is to be installed. Typically the builder does not identify the exact make or model at this point during the process. The Plans Examiner is responsible for verifying that the specified equipment efficiency complies with the Appliance Efficiency Regulations.
Field Inspection (Enforcement)
It is the responsibility of The Field Inspector to visually verify that the product information on the installed HVAC equipment matches the efficiency that was approved by the Plans Examiner. To facilitate the inspection process the Field Inspector may reference the CF2R-MCH-01-H form submitted by the builder/installing contractor. Additionally, the Field Inspector must also verify that the installed HVAC equipment is certified to the Energy Commission. The Field Inspector, at their discretion, may require the builder/installing contractor to provide a print out from the Energy Commission Appliance Efficiency Database of certified equipment listing the same make and model that is installed.
If the specifications labeled on the HVAC equipment do not match the equipment specifications on the Energy Commission Appliance Efficiency Database, the Inspector shall issue a correction notice to the builder/installing contractor. The following statement may be used as a correction notice.
On June 27, 2011 the U.S. Department of Energy adopted new federal air conditioner efficiency standards. For California those federal standards require efficiencies of SEER 14 and EER 12.2 for central split system air conditioners smaller than 45,000 Btu/hr (a SEER 14 and EER of 11.7 is required for larger central split system air conditioners). The new federal standards go into effect on January 1, 2015, which is six months after the July 1, 2014 effective date of the 2013 Standards. For performance approach simulations for projects subject to building permits (newly constructed buildings, additions and alterations to existing buildings) applied for after December 31, 2014, the compliance software will use a standard design that has been updated for the new federal standards.
In the past production builders have found it to be disruptive to have federal appliance efficiency standards change in the middle of a California Building Energy Efficiency Standards code cycle. They have preferred that for the entire period of the code cycle, that energy performance compliance be determined based on compliance both with the California building standards requirements plus the federal appliance efficiency standards. In that way they can build out their subdivisions with measures that remain consistent throughout the code cycle, rather than have to track and cope with a change in those measures in the middle of the cycle, which results in different customers receiving homes with different levels of energy efficiency. Other builders may prefer to cope with that change in the middle of the cycle, and build homes prior to the effective date of the federal standards that have a worse efficiency (and likely lower construction cost) than the homes that they build after the effective date of the
Building HVAC Requirements – Heating Equipment
The Energy Commission will direct compliance software developers to provide either approach to builders so they can choose which approach to take. Based on the builder’s choice the software will automatically determine whether compliance has been achieved.
For projects with permits applied for between July 1, 2014 and December 31, 2014 builders have two choices:
Option 1: Choose to Change the Efficiency for Their Homes in the Middle of the Code Cycle. Install equipment that meets the SEER 13 requirements of the current federal air conditioner standards. The software will compare the efficiency of the installed equipment against a standard design of SEER 13 to determine to what extent the building complies with the Building Standards. Starting January 1, 2015 the standard design will change to match the new federal air conditioner standards. After that point in time builders will have to improve the efficiency of the air conditioners they install to be equal to or better than the new federal air conditioner standards, and the efficiency measures required in the rest of the house may have to change to comply with the Building Standards depending on the air conditioner efficiencies that they choose.
Option 2: Choose to Build a Constant Efficiency for their Homes Throughout the Code Cycle. Install higher efficiency air conditioners that meet the new federal air conditioner efficiency standards. The software will compare the higher efficiency of the installed air conditioner against a standard design that meets the new federal air conditioner efficiency standards. Builders will be able to install the same air conditioner efficiency before and after the federal air conditioner standards effective date; expectations are that the construction costs will come down after the effective date as manufacturers are competing to offer equipment compliant with the new federal standards at lowest cost – this cost competition also may occur earlier than the effective date, as manufacturers endeavor to gain a competitive advantage ahead of the effective date. Builders will be able to install other building energy efficiency measures in their homes throughout the code cycle without having to have a disruptive change in what their crews are installing, and can avoid customers receiving homes that have different efficiency levels and measures in the middle of the code cycle.
This section addresses the requirements for heating equipment, including furnaces, boilers, heat pumps and electric resistance equipment.
A. Equipment Efficiency
§110.1 and §110.2(a) Appliance Efficiency Regulations
The efficiency of most heating equipment is regulated by NAECA (the federal appliance standard) and the California Appliance Efficiency Regulations. These
regulations are not contained in the Building Energy Efficiency Standards but are published separately. These regulations are referenced in §110.1. The Appliance Efficiency Regulations include definitions for all types of equipment and are scheduled to be updated January 1, 2015, which may change the minimum efficiencies of most equipment.
Note: The Appliance Efficiency Regulations that are in effect when the building permit is applied for will determine the minimum efficiency of the appliances identified in the compliance documentation.
The energy efficiency of other equipment is regulated by §110.2(a). Also, see the Nonresidential Compliance Manual for more information on larger equipment.
1. Gas and Oil-Fired Furnaces The current Appliance Efficiency Regulations require that the Annual Fuel Utilization Efficiency (AFUE) of all new gas and oil-fired central furnaces with a single phase electrical supply be at least 78% with an output capacity less than 225,000 Btu/hr. Gas and oil-fired central furnaces with outputs greater than or equal to 225,000 Btu/hr are rated according to their Thermal (or Steady State) Efficiency. The minimum Thermal Efficiency for large gas furnaces is 80% and 81% for large oil-fired central furnaces.
Table 4-1 – Minimum Efficiency for Gas and Oil-Fired Central Furnaces
Weatherized gas central furnaces with single phase electrical supply
Non-weatherized gas and oil central furnaces with single phase electrical supply
Weatherized oil central furnaces with single phase electrical supply
Non-weatherized oil central furnaces with single phase electrical supply
Gas central furnaces
≥ 225,000
Oil central furnaces
Source: California Appliance Efficiency Regulations Title-20 - Table E-4
Non-central gas furnaces and space heaters shall be certified to have AFUE values greater than or equal to those listed in below:
Table 4-2 – Minimum Heating Efficiency for Non-Ducted, Non-Central Gas Fired Heating Equipment
up to 42,000 Btu/hour
over 42,000 Btu/hour
up to 10,000 Btu/hour
over 10,000 Btu/hour up to 12,000 Btu/hour
over 12,000 Btu/hour up to
over 15,000 Btu/hour up to 19,000 Btu/hour
over 19,000 Btu/hour up to 27,000 Btu/hour
over 27,000 Btu/hour up to 46,000 Btu/hour
over 46,000 Btu/hour
up to 37,000 Btu/hour
over 37,000 Btu/hour
up to 18,000 Btu/hour
over 18,000 Btu/hour up to 20,000 Btu/hour
over 20,000 Btu/hour up to 27,000 Btu/hour
Source: California Appliance Efficiency Regulations Title-20 - Table E-2
2. Heat Pumps and Electric Heating Heat pumps shall be certified to have a HSPF or COP equal to or better than those listed in Table 4-3 below:
Table 4-3 – Minimum Heating Efficiency for Heat Pumps
Minimum Heating Efficiency
Before 10/08/2012
Cap /1000) =
Newly constructed or newly
conditioned buildings or
3.2-(0.026 x
After 10/08/2013
3.7-(0.052 x
Cap /1000) = COP
2.9-(0.026 x Cap1/1000) = COP
< 65,000 Btu/h Cooling
Packaged 7.7 HSPF
Capacity prior to 1/1/2015
Split 7.7 HSPF
Packaged 8.0 HSPF
Capacity effective 1/1/2015
Split 8.2 HSPF
Packaged 7.4 HSPF
< 65,000 Btu/h Cooling Capacity
Small duct high velocity < 65,000 Btu/h Cooling Capacity
≥ 65,000 and <135,000
≥ 135,000 and <240,000
≥ 240,000 and <760,000
≥ 135,000 Btu/h, < 240,000 Btu/h
2.9 COP
< 65,000 Single Phase
< 65,000 3-Phase
≥ 65,000 and < 135,000
≥ 135,000 and < 240,000
1. Cap = Cooling Capacity
Source: California Appliance Efficiency Regulation and Energy Efficiency Standards Title-20
There are no minimum appliance efficiency standards for electric-resistance or electric-radiant heating systems.
3. Gas and Oil-Fired Central Boilers and Electric Boilers Gas and oil-fired central boilers shall be certified to have and AFUE or Combustion Efficiency equal to or better than those listed in Table 4-4 below:
Table 4-4 – Minimum Efficiency for Gas and Oil Fired Central Boilers
Minimum Efficiency (%) Combustion Efficiency at
Gas steam boilers with single phase electrical supply
Gas hot water boilers with single phase electrical supply
82 ¹,²
Oil steam boilers with single phase electrical supply
Oil hot water boilers with single phase electrical supply
All other boilers with single phase electrical supply
Gas packaged boilers Oil packaged boilers
¹ No constant burning pilot light design standard. ² Automatic means for adjusting temperature design standard.
Source: California Appliance Efficiency Regulations Title-20 Table E-3
B. Heating System Controls
§150.0(i), 110.2(b), Exceptions to §110.2(b), 110.2(c), Exception to
110.2(c)
All unitary heating systems, including heat pumps, must be controlled by a setback thermostat. These thermostats must be capable of allowing the occupant to program the temperature set points for at least four different periods in 24 hours. For example, the setback thermostat could be programmed at specific temperature starting at 6:30 am, 9:00 am, 4:30 pm and 9:00 pm, thus allowing for four periods within 24 hours.
If the heating system is integrated into a central energy management control system (EMCS), then that system does not need to comply with the set back requirements. Additionally, all gravity gas wall heaters, floor heaters, room heaters and fireplaces, decorative gas appliances, wood stoves and non-central electric heaters do not need to be controlled by a setback thermostat.
Any heat pump with supplementary electric resistance heating must have controls that have two capabilities to limit the electric resistance heating. The first is to set the cut- on and cut-off temperatures for compression and supplementary heating at different
For example, if the heat pump begins heating when the inside temperature reaches 68°F, the electric resistance heating is set to come on if the temperature gets below 65°F; and there is an opposite off mode such that if the heat pump shuts off when the temperature reaches 72°F, the back-up heating shuts off at 68°F.
The second control capability prevents the supplementary electric resistance heater from operating when the heat pump alone can meet the heating load, except during defrost. There is a limited exception to this second function for “smart thermostats” that provide the following: intelligent recovery, staging, ramping, or another control mechanism that prevents the unnecessary operation of supplementary electric resistance heating when the heat pump alone can meet the heating load.
To meet the thermostat requirements, a thermostat for a heat pump must be a “smart thermostat” that minimizes the use of supplementary heating during startup and recovery from setbacks.
Note: Room air conditioner heat pumps are not required to comply with the thermostat requirements.
C. Equipment Sizing
§150.0(h)1 and 2
The Standards do not set limits on the sizing of heating equipment, but they do require that heating loads be calculated for new heating systems. Oversized equipment typically operates less efficiently and can create comfort problems due to excessive cycling and high airflow.
Acceptable load calculation procedures include methods described in
1. The ASHRAE Handbook – Equipment,
2. The ASHRAE Handbook – Applications,
3. The ASHRAE Handbook – Fundamentals,
4. The SMACNA Residential Comfort System Installation Manual, or
5. ACCA Manual J.
The Standards require that the outdoor design conditions for load calculations be selected from Reference Joint Appendix JA2, and that the indoor design temperature for heating load calculations be 68°F.
The outdoor design temperature must be no lower than the “heating winter median of extremes” as listed in the Reference Joint Appendix JA2.
If the actual city location for a project is not included in the Reference Joint Appendix JA2, or if the data given for a particular city does not match the conditions at the actual site as well as that given for another nearby city, consult the local building department for guidance.
The load calculations must be submitted with the compliance documentation when requested by the building department.
The load calculations may be prepared by 1) a mechanical engineer, 2) the mechanical contractor who is installing the equipment or 3) someone who is qualified to do so in the State of California according to Division 3 of the Business and Professions Code.
D. Furnace Temperature Rise
§150.0(h)4
High temperature rise in a furnace is an indicator of low airflow and/or over specification firing rate. High temperature rise causes low efficiency and is potentially damaging to the furnace. Central forced-air heating furnace installations must be configured to operate at or below the furnace manufacturer's maximum inlet-to-outlet temperature rise specification.
E. Standby Losses and Pilot Lights
§110.5 and §110.2(d)
Fan-type central furnaces may not have a continuously burning pilot light. This requirement does not apply to wall furnaces, floor furnaces or any gravity type furnace. Household cooking appliances also must not have a continuously burning pilot light except for those without an electrical supply voltage connection and in which each pilot consumes less than 150 Btu/hr.
Larger gas-fired and oil-fired forced air furnaces with input ratings ≥ 225,000 Btu/h (which is bigger than a typical residential furnace) must also have an intermittent ignition or interrupted device (IID), and either power venting or a flue damper.
A vent damper is an acceptable alternative to a flue damper for furnaces where combustion air is drawn from the conditioned space. All furnaces with input ratings ≥ 225,000 Btu/h, including electric furnaces, that are not located within the conditioned space must have jacket losses not exceeding 0.75 percent of the input rating.
F. Pipe Insulation
§150.0(j)2C, §150.0(j)3, §120.3
The piping for heat pumps and for both steam and hydronic heating systems with an operating pressure above 15 psig (103kPa) shall meet the requirements from
Table 4-5, which can be found below. When the insulation is located outside conditioned space it is required to be protected from damage caused by environmental conditions. The insulation must be rated for outdoor use or covered with a material that can withstand the outdoor conditions. Examples of these types of coverings are aluminum, sheet metal, painted canvas, plastic cover or if the insulation is cellular foam, a coating that is water retardant and shields from solar radiation. Additionally, the insulation used for the refrigerant suction line of a heat pump must be Class I or Class II vapor retarding. If the insulation is not Class I or Class II, then the insulation must be installed at the required thickness that would qualify it as a Class I or Class II vapor retarder.
Table 4-5 - Insulation Requirements for Heating System Piping
Range (in Btu-inch per
Insulation Mean
Range ( o F)
per ( o F)
Temperature( o F)
Space heating, Hot Water systems (steam, steam condensate and hot water), Service Water Heating Systems
Heat Pump Suction Line
From Table 120.3 A of the Building Energy Efficiency Standards Title-20
§150.1(c)6 Heating System Type
Prescriptive Component Package A requires that a gas heating system or a heat pump be installed. The minimum energy efficiency of the heating equipment is specified by the mandatory measures (see above).
Supplemental heating systems are allowed prescriptively and the designer may elect to provide supplemental heating to a space such as a bathroom. In this instance, supplemental heating system must be installed in a space that is served by the primary heating system and must have a thermal capacity of less than 2 kW or 7,000 Btu/hr while being controlled by a time-limiting device not exceeding 30 minutes. Electric resistance and electric radiant heating is only allowed to be installed as the primary heating system when using the performance compliance method as described in Section 4.2.3.
Using the prescriptive compliance approach, no additional credit is given for selecting equipment that is higher than what is required by the prescriptive component package.
There is one option for receiving compliance credit related to the heating system. This credit is available through the performance compliance method.
Heating system efficiencies are explained above in section 4.2.2 and the minimum efficiency is required per the prescriptive package. With the performance compliance method, compliance credit is awarded for selecting higher efficiency heating equipment, such as a high efficiency furnace or heat pump. With a furnace, for
Building HVAC Requirements – Cooling Equipment
example, selecting an AFUE higher than 78 will result in compliance credit which can then be used to offset other building features that do not satisfy the prescriptive requirements but that do comply with the mandatory requirements.
This section addresses the requirements for space cooling equipment.
§110.1 and §110.2(a) and the Appliance Efficiency Regulations
The efficiency of most cooling equipment is regulated by NAECA (the federal appliance standard) and the California Appliance Efficiency Regulations. These regulations are not contained in the Building Energy Efficiency Standards but rather in separate documents. These regulations are referenced in §110.1. The Appliance Efficiency Regulations include definitions for all types of equipment. The energy efficiency of larger equipment is regulated by §110.2(a). See the Nonresidential Compliance Manual for information on larger equipment.
1 Central, Single Phase Air Conditioners and Air Source Heat Pumps (under 65,000 Btu/h) The central, single phase air conditioners and air source heat pumps that are most commonly installed in residences have a smaller capacity than 65,000 Btu/h. The Appliance Efficiency Regulations for this equipment require minimum Seasonal Energy Efficiency Ratios (SEER). The Seasonal Energy Efficiency Ratio of all new central, single phase air conditioners and air source heat pumps with output less than 65,000 Btu/h shall be certified to the Energy Commission to have values no less than the values listed below in Table 4-6.
Table 4-6 – Minimum Cooling Efficiencies for Central Air Conditioners and Heat Pumps
Eff Before
Eff 1/1/2015
<45,000 Btuh
≥45,000 Btuh
Central Air Source Heat Pumps
Space Constrained Air Conditioner
Space Constrained Heat Pump
10.9 NR
10.6 NR
Through-The-Wall Heat
Small Duct, High Velocity Air Conditioner
Small Duct, High Velocity Heat Pump
Source: California Appliance Efficiency Regulations Table C-2 Title-20
2 Other Air Conditioners and Heat Pumps
The current Appliance Efficiency Regulations for larger central air conditioners and heat pumps, and for all room air conditioners and room air conditioner heat pumps shall be certified to the Energy Commission by the manufacturer to have values no less than the values listed in Table 4-7 and Table 4–8.
Table 4-7 – Minimum Cooling Efficiency for Larger Central Air Conditioners and Heat Pumps
≥65,000 Btu/h but <135,000 Btu/h
≥135,000 Btu/h but <240,000 Btu/h
≥240,000 Btu/h but <760,000 Btu/h
≥ 65,000 Btu/h but <135,000 Btu/h
Central Water Source Heat Pumps
≥ 17,000 Btu/h and < 135,000 Btu/h
≥ 135,000 Btu/h and < 240,000 Btu/h
< 17,000 < 65,000 Btu/h
1 Applies to equipment that has electric resistance heat or no heating.
2 Applies to equipment with all other heating-system types that are integrated into the unitary equipment. Source: California Appliance Efficiency Regulations Table C-3, C-5
Table 4-8 – Minimum Cooling Efficiency for Non-Central Space Cooling Equipment
Including Room Air Conditioners; and Room Air Conditioner Heat Pumps; Package Terminal Air Conditioners (PTAC); Package Terminal Heat Pumps (PTHP), Single Package Vertical Air Conditioners (SPVAC) and Heat Pumps (SPVHP)
≥ 6,000 Btu/h and - 7,999 Btu/h
≥ 8,000 Btu/h and -13,999 Btu/h
9.8EER
≥ 14,000 Btu/h and - 19,999 Btu/h
≥ 8,000 and - 19,999 Btu/h
Room Air Conditioner Heat Pumps
8.5EER
Casement-Only Room Air Conditioner
Casement-Slider Room Air Conditioner
PTAC (cooling mode) Newly
After 10/08/2012
constructed or newly conditioned buildings or additions
12.5-(0.213 x Cap/1000) = EER
13.8-(0.300 x Cap/1000) = EER
PTAC (cooling mode) Replacements
10.9-(0.213 x Cap/1000) = EER
PTHP (cooling mode) Newly
12.3-(0.213 x Cap/1000) = EER
14.0-(0.300 x Cap/1000) = EER
PTHP (cooling mode) Replacements
10.8-(0.213 x Cap/1000) = EER
Cap. = Cooling Capacity (Btu/hr)
Source: California Appliance Efficiency Regulations the Energy Efficiency Standards Title -20
B. Insulation for Refrigerant Lines in Split System Air Conditioners
§150.0(j)2 and 3, §150.0(m)9 Two refrigerant lines connect the indoor and outdoor units of split system air conditioners and heat pumps: the liquid line (the smaller diameter line) and the suction line (the larger diameter line). The liquid line is at an elevated temperature relative to outdoor and indoor temperatures, in those areas, heat escaping from it is helpful; therefore, it should not be insulated. When the liquid line runs through the attic, its surrounding temperature is higher than the liquid line temperature. It would be advantageous to insulate liquid lines running through attics. The suction line carries refrigerant vapor that is cooler than ambient in the summer and (with heat pumps) warmer than ambient in the winter. This line must be insulated to the required thickness (in inches) as specified in the table below.
Table 4-9 – Insulation Requirements for Split System Refrigerant Piping
per o F
Space cooling systems suction line
From Table 120.3-A of the Building Energy Efficiency Standards
Insulation used for the suction line must be protected from physical damage or from UV deterioration when it is located in outside conditioned space. Pipe insulation is typically protected by an aluminum or sheet metal jacket, painted canvas, plastic cover, or coating that is water retardant and UV resistant. Additionally, the insulation used for the refrigerant suction line of a heat pump must be Class I or Class II vapor retarding. If the insulation is not Class I or Class II, then the insulation must be installed at the required thickness that would qualify it as a Class I or Class II vapor retarder. See §150.0(j) 3, and Figure 4-1.
Figure 4-1 – Refrigerant Line Insulation
C. Outdoor Condensing Unit Clearance
§150.0(h)3
Any obstruction of the airflow through the outdoor unit of an air conditioner or heat pump lowers its efficiency. Dryer vents are prime sources for substances that clog outdoor coils and sometimes discharge substances that can cause corrosion. Therefore, condensing units shall not be placed within 5 feet of a dryer vent. Regardless of location, condenser coils should be cleaned regularly in all homes.
Figure 4-2 – Non-compliant Condensing Unit Clearance from Dryer Vents
§150.0(h)
Similar to heating equipment, the Standards do not set limits on the size of cooling equipment, but they do require that cooling loads be calculated for new cooling systems. Avoiding oversizing is especially important for cooling equipment because ducts must be sized large enough to carry the mandatory airflow and oversized air conditioners make this difficult.
The outdoor design conditions for load calculations must be selected from Reference Joint Appendix JA2, Table 2-3, using values no greater than the “1.0 percent Cooling Dry Bulb” and “Mean Coincident Wet Bulb” values listed. The indoor design temperature for cooling load calculations must be 75°F. Acceptable load calculation procedures include methods described in
5. ACCA Manual J
Cooling load calculations must be submitted with compliance documentation when requested by the building department. The load calculations may be prepared by 1) a mechanical engineer, 2) the mechanical contractor who is installing the equipment or 3) someone who is qualified to do so in the State of California according to Division 3 of the Business and Professions Code.:
E. Hole for Static Pressure Probe (HSPP) or Permanently Installed Static Pressure Probe (PSPP)
§150.0(m)13
Space conditioning systems that utilize forced air ducts to supply cooling to occupiable space shall have a hole for the placement of a static pressure probe (HSPP) or permanently installed static pressure probe (PSPP) installed downstream from the evaporator coil.
The HSPP or PSPP must be installed in the required location, in accordance with the specifications detailed in Reference Residential Appendix RA3.3. The HSPP or PSPP is required in order to facilitate system airflow measurement when using devices/procedures that depend on supply plenum pressure measurements. The HSPP or PSPP allows HERS raters to perform the required diagnostic airflow testing in a non-intrusive manner, by eliminating the necessity for the rater to drill holes in the supply plenum for placement of pressure measurement probes.
The size and placement of the HSPP/PSPP shall be in accordance with RA3.3.1.1 and shall be verified by a HERS rater. In the event that the HSPP/PSPP cannot be installed as shown in Figure RA3.3-1, due to the configuration of the system or that the location is not accessible, an alternative location may be provided that can accurately measure the average static pressure in the supply plenum. If an alternative location cannot be provide then the HSPP/PSPP is not required to be installed. The HERS
rater will verify this. Note that not installing an HSPP/PSPP will limit the airflow measurement method to either a powered flowhood or passive (traditional) flow hood.
When the mandatory measure for minimum system airflow rate is in effect (entirely new systems), there must be a hole in the supply plenum, provided by the installing contractor, for the placement of a static pressure probe (HSPP). Alternatively a permanently installed static pressure probe (PSPP) must be installed in the same location.
This requirement also applies when the plenum pressure matching method or the flow grid method of airflow measurement is used by either the installer or the rater to verify airflow in an altered system. Note that the HSPP/PSPP must be installed by the installer, not the rater.
See Air Distribution Ducts, Plenums, and Fans Section 4.4 for discussion regarding mandatory sizing/airflow requirements for ducted systems with cooling.
§150.1(c)7
The Prescriptive Component Packages do not require that a cooling system be installed. However if one is to be installed, the cooling equipment efficiency requirements are specified by the mandatory measures (see above). Using the prescriptive compliance approach, no additional credit is given for selecting equipment that is higher than what is required by the prescriptive component package.
Prescriptive Component Package A, for split system equipment in climate zones 2 and 8 through 15, requires refrigerant charge verification (RCV) and the installation of a measurement access hole (MAH). The RCV must be performed by the installer and/or HERS rater. The MAH provides a non-intrusive means of measuring return air temperature, which is a parameter important to the RCV process. The alternative to RCV is the installation of a refrigerant charge indicator display (§151(f)7Aia).
A. Refrigerant Charge Verification (RCV) The prescriptive standards require that a HERS rater verify that air-cooled air conditioners and air-source heat pumps have the correct refrigerant charge. The RCV procedures are documented in Reference Residential Appendix RA3.2, and RA1.2. Refrigerant charge refers to the actual amount of refrigerant present in the system. Excessive refrigerant charge (overcharge) reduces system efficiency and can lead to premature compressor failure. Insufficient refrigerant charge (undercharge) also reduces system efficiency and can cause compressors to overheat. Ensuring correct refrigerant charge can significantly improve the performance of air conditioning equipment. Refrigerants are the working fluids in air conditioning and heat pump systems that absorb heat energy from one area (the evaporator),transfer and reject it to another (the condenser).
B. Note: The Refrigerant Charge Verification process is discussed in greater detail later in Section 4.9.Measurement Access Hole (MAH) MAH provide a non-intrusive means for refrigerant charge verification by HERS raters and other third party inspectors, since they eliminate the need for the raters/inspectors to drill holes into the installed air conditioning equipment enclosures for placement of the temperature sensors that are required by the refrigerant charge verification test
procedures described in the Reference Residential Appendix RA3.2.
Installation of MAH must be performed by the installer of the air conditioner or heat pump equipment according to the specifications given in Reference Residential Appendix RA3.2.
The MAH feature consists of one 5/8 inch (16 mm) diameter hole in the return plenum, upstream from the evaporator coil (see figure RA3.2-1 in Reference Residential Appendix RA3.2).
C. Charge Indicator Display The installation of a charge indicator display (CID) may be used as an alternative to the prescriptive requirement for HERS diagnostic testing of the refrigerant charge in split system air conditioners and heat pumps. The purpose of the CID is to provide real-time information to the building occupant about the status of the system refrigerant charge, metering device, and system airflow. The CID will monitor and determine the operating performance of split system air conditioners and heat pumps, and provide visual indication to the system owner or operator if the system’s refrigerant charge, airflow, or metering device performance does not conform to approved target parameters for minimally efficient operation. Thus, if the CID signals the owner/occupant that the system requires service or repair, the occupant can immediately call for a service technician to make the necessary adjustments or repairs. A CID can provide significant benefit to the owner/occupant by alerting the owner/occupant to the presence of inefficient operation that could result in excessive energy use/costs over extended periods of time. A CID can also indicate system performance faults that could result in system component damage or failure if not corrected, thus helping the owner/occupant to avoid unnecessary repair costs. The CID procedures are documented in Reference Residential Appendix RA4.3.2. Charge indicator display technologies shall be factory installed or field installed according to manufacturer's specifications. Reference Joint Appendix JA6 contains more information about CID technologies. The presence of a CID on a system must be field verified by a HERS rater. See Reference Residential Appendix RA3.4.2 for the HERS verification procedure, which consists of a visual verification of the presence of the installed CID technology. The rater must inspect to see that the visual indication display component of the installed CID technology is mounted adjacent to the split system's thermostat. When the outdoor temperature is greater than 65°F, the rater must also observe that the system reports no system faults when the system is operated continuously for at least 15 minutes when the indoor air temperature returning to the air conditioner is at or above 70°F. When the outdoor temperature is below 65°F the Rater must observe that the CID does a self diagnosis and indicates that the sensors and internal processes are operating properly. Though not specifically mentioned in the CID protocols of Residential Appendix RA3.4.2, the Winter Set Up Method detailed in RA 1.2 may be used when normally allowed. For purposes of CID verification the Winter Setup Method will be treated the same as the Subcooling Method.
There are several options for receiving compliance credit related to the cooling system. These credits are available through the performance compliance method.
A. High Efficiency Air Conditioner Air conditioner efficiencies are determined according to federal test procedures. The efficiencies are reported in terms of Seasonal Energy Efficiency Rating (SEER) and Energy Efficiency Rating (EER). Savings can be achieved by choosing an air conditioner that exceeds the minimum efficiency requirements. The EER is the full load efficiency at specific operating conditions. It is possible that two units with the same SEER can have different EERs. In cooling climate zones of California, for two units with a given SEER, the unit with the higher EER is more effective in saving energy. Using the performance compliance method, credit is available for specifying an air conditioner with an EER greater than 10 (see the compliance program vendor’s compliance supplement). When credit is taken for a high EER or SEER, field verification by a HERS rater is required (see Reference Residential Appendix RA3.4).
B. Air Handler Watt Draw and System Airflow It is mandatory that central forced air systems produce fan watt draws less than or equal to 0.58 watts/CFM and flow at least 350 CFM per nominal cooling ton. Performance compliance credits are available for demonstrating the installation of a high efficiency system with a lower fan wattage and/or higher airflow than the mandatory requirements. These credits can be achieved by selecting good duct design and can be assisted by a high efficiency fan. There are two possible performance compliance credits:
1. The performance compliance method allows the user’s proposed fan watt draw to be entered and credit earned if it is lower than the default of 0.58 watts per CFM of system airflow. To obtain this credit, the system airflow must meet the mandatory requirement of at least 350 CFM/ton of nominal cooling capacity.
2. The performance compliance method allows the user’s proposed airflow to be entered and credit earned if it is higher than the default of 350 CFM/ton of nominal cooling capacity. To obtain this credit, the fan watt draw must meet the mandatory requirement of no more than 0.58 Watts per CFM of nominal cooling capacity.
After installation, the contractor must test the actual fan power and airflow of the system using the procedure in Reference Residential Appendix RA3.3, and show that it is equal or better than what was proposed in the compliance software analysis.
Field verification by a HERS rater is required (see Reference Residential Appendix
RA3.3).
Building HVAC Requirements – Air Distribution System Ducts, Plenums, and Fans
Air distribution system performance can have a big impact on overall HVAC system efficiency. Therefore, air distribution systems face a number of mandatory measures and prescriptive requirements, discussed below.
The 2013 Standards specify mandatory requirements for air distribution ducts to be sealed and tested in all climate zones. There are also a number of compliance credits available related to duct system design.
Duct efficiency is affected by the following parameters:
1. Duct location (attic, crawlspace, basement, inside conditioned space, or other)
2. Specific conditions in the unconditioned space, e.g., presence of a radiant barrier
3. Duct insulation characteristics
4. Duct surface area, and
5. Air leakage of the duct system
In performance calculations, duct efficiency can be calculated in one of two ways:
1. default input assumptions; or
2. diagnostic measurement values.
The computer program will use default assumptions for the proposed design when the user does not intend to make improvements in duct efficiency.
A. Minimum Insulation
§150.0(m)1
In all cases, unless ducts are enclosed entirely in directly conditioned space, the minimum allowed duct insulation value is R-6. Note that higher values may be required by the prescriptive requirements as described below.
To determine whether ducts are enclosed entirely in directly conditioned space as it is defined in Section 100.1, a rater must field verify by visual inspection and by using the
RA3.1.4.3.8.
RA3.1.4.3.8 utilizes a duct leakage to outside test procedure to help ensure that the ducts are within the pressure boundary of the space being served by the duct system. Passing the test alone is not enough to establish that the ducts are entirely within directly conditioned space. The test procedure is in addition to a basic visual inspection of the ducts to ensure that no portion of the duct system is obviously outside of the apparent pressure/thermal boundary. Once this has been established, the leakage to outside test verifies that the pressure boundary is intact and preventing leakage from escaping to the outside.
Applying this procedure to multi-family dwelling units poses a unique situation. In this case leakage to “outside” means conditioned air leaking from the ducts to anywhere outside of the pressure boundary of the space being served by the duct system, including adjacent dwelling units. Duct leakage to adjacent dwelling units is not
desirable and should be eliminated. When performing the leakage to outside test, it is only necessary to pressurize the dwelling unit served by the duct system being tested.
§150.0(m)1 Exception to §150.0(m)1
Ducts and fans integral to a wood heater or fireplace are exempt from Standards Section 150.0(m)1.
§150.0(m)5
For the purpose of determining installed R-value of duct insulation based on thickness, when not an integral part of a manufacturer-labeled, insulated duct product such as vinyl flex duct, the following shall be used:
1. For duct wrap, the installed thickness of insulation must be assumed to be 75 percent of the nominal thickness due to compression.
2. For duct board, duct liner and factory-made rigid ducts not normally subjected to compression, the nominal insulation thickness shall be used.
B. Connections and Closures
§150.0(m)1, §150.0(m)2, §150.0(m)3
Note: Duct installation requirements are discussed in more detail in Duct Installation Standards Section 4.4.3
The Standards set a number of mandatory measures related to duct connections and closures. These measures address both the materials and methods used for duct sealing. The following is a summary. Refer to the sections of the Standards listed above for additional details.
C. Factory-fabricated Duct Systems
Factory fabricated duct systems must comply with the following requirements:
1. All factory-fabricated duct systems must comply with UL 181 for ducts and closure systems, including collars, connections, and splices, and be labeled as complying with UL 181. UL181 testing may be performed by UL laboratories or a laboratory approved by the Executive Director.
2. All pressure-sensitive tapes, heat-activated tapes, and mastics used in the manufacture of rigid fiberglass ducts must comply with UL 181 and UL
3. All pressure-sensitive tapes and mastics used with flexible ducts must comply with UL 181 and UL 181B.
4. Joints and seams of duct systems and their components cannot be sealed with cloth back rubber adhesive duct tapes unless such tape is used in combination with mastic and draw bands: or
5. It has on its backing the phrase "CEC approved," a drawing of a fitting to plenum joint in a red circle with a slash through it (the international symbol of prohibition), and a statement that it cannot be used to seal fittings to plenums and junction box joints.
D. Field-fabricated Duct Systems Field –fabricated duct systems must comply with the following requirements:
1. Factory-made rigid fiberglass and flexible ducts for field-fabricated duct systems must comply with UL 181. All pressure-sensitive tapes, mastics, aerosol sealants, or other closure systems used for installing field-fabricated duct systems shall meet the applicable requirements of UL 181, UL 181A, and UL 181B.
2. Mastic sealants and mesh:
a. Sealants must comply with the applicable requirements of UL 181, UL 181A, and/or UL 181B, and be nontoxic and water resistant.
b. Sealants for interior applications must be tested in accordance with ASTM C731 and D2202.
c. Sealants for exterior applications must be tested in accordance with ASTM C731, C732, and D 2202.
d. Sealants and meshes must be rated for exterior use.
3. Pressure-sensitive tapes must comply with the applicable requirements of UL 181, UL 181A, and UL 181B.
4. Joints and seams of duct systems and their components must not be sealed with cloth back rubber adhesive duct tapes unless such tape is used in combination with mastic and draw bands: or
5. It has on its backing the phrase "CEC approved," a drawing of a fitting to plenum joint in a red circle with a slash through it (the international symbol of prohibition), and a statement that it cannot be used to seal fittings to plenums or junction box joints.
E. Draw Bands Used With Flexible Duct
1. Draw bands must be either stainless-steel worm-drive hose clamps or UV- resistant nylon duct ties.
2. Draw bands must have a minimum tensile strength rating of 150 pounds.
3. Draw bands must be tightened as recommended by the manufacturer with an adjustable tensioning tool.
F. Aerosol-sealant Closures
1. Aerosol sealants shall meet the requirements of UL 723 and be applied according to manufacturer specifications.
2. Tapes or mastics used in combination with aerosol sealing shall meet the requirements of this Section.
If mastic or tape is used to seal openings greater than 1/4 inch, the combination of mastic and either mesh or tape must be used.
Building spaces such as cavities between walls, support platforms for air handlers, and plenums defined or constructed with materials other than sealed sheet metal, duct board, or flexible duct must not be used for conveying conditioned air including return air and supply air. The practice of using drywall materials as the interior surface of a return plenum is not allowed. Building cavities and support platforms may contain ducts. Ducts installed in cavities and support platforms must not be compressed to cause reductions in the cross sectional area of the ducts. Although a HERS rater may examine this as a part of his or her responsibilities when involved in a project, the
enforcement of these minimum standards for ducts is the responsibility of the building official.
§150.0(m)2D, §150.0(m)3D
Duct systems may not use cloth-back, rubber-adhesive duct tape (typical, “old fashion”, non-rated duct tape) unless it is installed in combination with mastic and draw bands. Note: mastic and drawbands alone are adequate for sealing most connections. Cloth back rubber adhesive duct tape would then only be used to hold the outer vapor barrier in place or for some other superfluous purpose. It alone is not adequate to serve as an air sealing method or as a mechanical connection.
The enforcement of these minimum standards is normally the responsibility of the building official; however HERS raters will also verify compliance with this requirement in conjunction with duct leakage verification.
G. Product Markings
§150.0(m)2A, §150.0(m)6
All factory-fabricated duct systems must meet UL 181 for ducts and closure systems and be labeled as complying with UL 181. Collars, connections and splices are considered to be factory-fabricated duct systems and must meet the same requirement.
Insulated flexible duct products installed to meet this requirement must include labels, in maximum intervals of 3 ft, showing the R-value for the duct insulation (excluding air films, vapor barriers, or other duct components), based on the tests and thickness specified in §150.0(m)4 and §150.0(m)5C.
H. Dampers to Prevent Air Leakage
§150.0(m)7
Fan systems that exhaust air from the building to the outside must be provided with back draft or automatic dampers.
§150.0(m)8
Gravity ventilating systems must have an automatic or readily accessible, manually operated damper in all openings to the outside, except combustion inlet and outlet air openings and elevator shaft vents. This includes clothes dryer exhaust vents when installed in conditioned space.
I. Protection of Insulation
§150.0(m)9
Insulation must be protected from damage, including that due to sunlight, moisture, equipment maintenance, and wind but not limited to the following:
Insulation exposed to weather must be suitable for outdoor service; for example, protected by aluminum, sheet metal, painted canvas, or plastic cover.
Cellular foam insulation shall be protected as above or painted with a coating that is water retardant and provides shielding from solar radiation that can cause degradation of the material.
J. Ducts in Concrete Slab
Ducts located in a concrete slab must have R-6 insulation but other issues will come into play. If ducts are located in the soil beneath the slab or embedded in the slab, the insulation material should be designed and rated for such installation. Insulation installed in below-grade applications should resist moisture penetration (closed cell foam is one moisture-resistant product). Common pre-manufactured duct systems are not suitable for below-grade installations. If concrete is to be poured directly over the ducts, then the duct construction and insulation system should be sturdy enough to resist the pressure and not collapse. Insulation should be of a type that will not compress, or it should be located inside a rigid duct enclosure. The only time that common flex ducts are suitable in a below-grade application is when a channel is provided in the slab.
K. Porous Inner Core Flex Duct
§150(m)10
Over time the outer vapor barrier of flex duct can be compromised. Therefore porous inner core flex duct is not allowed.
L. Duct System Sealing and Leakage Testing
§150(m)11
Duct system sealing and leakage testing is mandatory in all climate zones. Duct systems in newly constructed single family dwellings, townhouses, and multifamily dwellings are required to comply with the requirements. Alterations and additions to ducted systems in existing buildings in all climate zones are also required to comply with applicable maximum leakage criteria. Refer to Chapter 9 for more information on duct sealing and leakage testing for existing buildings.
Duct Leakage Testing For Multiple Duct Systems With Common Return Ducts
If there are two or more duct systems in a building that are tied together at a common return duct, then each duct system should be tested separately, including the shared portion of the return duct system in each test. Under this scenario, the portions of the second duct system that is not being tested must be completely isolated from the portions of the ducts that are being tested, so the leakage from second duct system does not affect the leakage rate from the side that is being tested.
The diagram below represents the systems that are attached to a shared return boot or remote return plenum. In this case, the point in the return system that needs to be blocked off is readily accessible through the return grille.
The “duct leakage averaging” where both system are tested together as though it is one large system and divide by the combined tonnage to get the target leakage may not be used as it allows a duct system with more the 6% leakage to pass if the combined system’s leakage is 6% or less.
Figure 4–3- Two Duct Systems with a Common Return Duct
M. Air Filtration
§150.0(m)12
Air filtration is present in forced air systems to protect the equipment and may provide health benefits to occupants of the building. In addition to filtering particulates from the airstream filters add flow resistance to the forced air system, potentially lowering the efficiency of the heating/cooling equipment. Flow resistance is measured as a pressure drop at a specific airflow.
Except for evaporative coolers, any mechanical forced air heating and/or cooling system with more than 10 feet of duct must meet four sets of criteria:
1. System Design Criteria:
a) All recirculated and outdoor air passing through the heating/cooling device must first pass through the filter.
b) The system design must accommodate the pressure drop through the filter at the designed airflow. In order to accomplish this, the design airflow and the design pressure drop through the filter must be determined by the designer. The design pressure drop will determine the size and depth of the filter media required for the device (return filter grill or filter rack).
c) If the system design elects compliance utilizing the Return Duct Design alternative specified in Tables 150.0-C and D, then the designer must assume a design filter pressure drop of 0.05 IWC at the applicable design airflow rate.
d) Replacing the filters, like for like, when they become dirty brings their resistance to airflow back to the design condition. Therefore, the filters must be located to allow access for regular service by the occupants.
e) To maintain the energy efficiency of the system it is necessary for the occupants to know which filters to select that will provide the designed airflow. Therefore, a clearly legible label, such as shown in Figure 4-6 shall be permanently placed in a location visible to a person changing the filter. As shown in Figure 4-6, the label shows the allowable maximum resistance at the airflow rate closest to the design airflow for that filter location. Figure 4-6 is an example of label for a filter location designed for 400 CFM at 0.03 IWC. Note that the standard AHRI 680 airflow values are given in 400 CFM increments. The filter media pressure drop specifications at the design airflow rates that fall between the 400 cfm increments must be determined by interpolation of the Standard 680 rating values, or by lookup methods made available by the filter media vendor or manufacturer.
AHRI 680 Standards Rating
USE ONLY REPLACEMENT FILTERS WITH
AN INTIAL RESISTANCE LESS THAN 0.032
AT 400 CFM
Figure 4-4 – Example of Filter Location Label
1. Air Filter Media Efficiency Criteria: The filter media shall be MERV 6 or better to provide protection to the equipment and to potentially provide health benefits. Filter media that provide at least 50% particle efficiency in the 3.0–10 μm range in AHRI
are considered to meet the MERV 6 criterion.
2. Air Filter Media Pressure Drop Criteria: To ensure airflow for efficient heating and cooling equipment operation, the installed filter media must conform to the design pressure drop specification shown in the Filter Location Label described in item 1e above.
3. Air Filter Media Labeling Criteria: The filter device must be provided with a filter media product that has been labeled by the manufacturer to disclose performance ratings that meet both the Efficiency and Pressure drop criteria described in 2, and 3 above and as shown in the Filter Location Label described in item 1e above.
N. Forced Air System Duct Sizing, Airflow Rate and Fan Efficacy
Adequate airflow is critical for heating and cooling equipment efficiency. Simultaneously, the watt draw of the fan producing the airflow is a portion of the efficiency. It is important to maintain adequate airflow without expending excessive fan watts to achieve the airflow. The airflow and watt draw must be HERS verified. See Reference Residential Appendices RA3.3 for the HERS verification procedures. The prescriptive return system does not have to be HERS verified.
Except for heating only systems, systems must comply with one of the following two
1. Airflow and Watt Draw measurement and determination of Fan Efficacy: When using the Airflow (cfm/ton) and Fan Efficacy (Watt/cfm) method the following criteria must be met:
a) Provide airflow through the return grilles that is equal to or greater than 350 CFM per ton of nominal cooling capacity.
b) At the same time the fan watt draw must be less than or equal to 0.58 Watts per CFM.
The methods of measuring the watt draw are described in Reference Residential Appendix RA3.3. Three acceptable apparatuses are:
a) a portable watt meter,
b) an analog utility revenue meter, or
c) a digital utility revenue meter.
There are three acceptable methods to determine compliance with the system airflow requirement. They are described in Reference Residential Appendix RA3.3 and use an:
a) active or passive flow capture hood to measure the total airflow through the return grill(s), or
b) flow grid device(s) at the return grill(s) or other location where all the central fan airflow passes through the flow grid, or
c) fan flow meter device to perform the plenum pressure matching procedure.
The flow grid measurement device and the fan flow meter measurement device both require access to static pressure measurements of the airflow exiting the cooling coil, which utilizes a HSPP or PSPP (Section RA3.3.1.1).
The contractor must install either a hole for the placement of a static pressure probe (HSPP) or provide a permanently installed static pressure probe (PSPP) as shown in Figure 4-7 below and Reference Residential Appendix RA3.3
5/16 inch Diameter Hole
Or Permanent Static
A = Supply Plenum/Coil Box
B = Supply Plenum/Coil Box
dimension perpendicular
Supply Plenum/Coil Box
Return Plenum/Blower
Figure 4–5 - Location of the Static Pressure Probe
The HSPP or PSPP facilitates cooling coil airflow measurement when using devices/procedures that depend on supply plenum pressure measurements.
2. Return Duct System Design Method – This method allows the designer to specify, and the contractor to install, a system that does not have to be tested for airflow and fan watt draw. This method can be used for return systems with two returns. Each return shall be no longer than 30 feet from the return plenum to the filter grille. When bends are needed, metal elbows are desirable. Each return can have up to 180 degrees of bend and no more 90 degrees of bend can be flex duct. To use this method, the designer and installer must provide return system sizing that meets the appropriate criteria in Table 150.0-C or D.
O. Airflow and Fan Efficacy Testing Versus Return Duct Sizing
Studies have shown that adequate airflow is critical to the efficient operation of air conditioning systems. Section 150.0(m)13B establishes mandatory requirements that are intended to ensure adequate cooling airflow through properly sized ducts and efficient fan motors.
There are two options allowed to ensure adequate air flow; option one is to design and install the systems using standard design criteria and then have the systems airflow and fan efficacy (AF/FE) tested and third-party verified in the field. The second option is to use size the return ducts according to Tables 150.0-C and D. These tables are very simplified and very conservative (the return ducts are much larger than would normally be used). They should only be used in situations where there is a serious concern that the system will not pass the diagnostic tests for airflow and fan efficacy, such as in alterations where duct modification opportunities are limited. The first option, AF/FE testing, is always
preferable, especially in new construction.
The California Green Code and the California Mechanical Code both require that residential duct systems be designed according to ACCA Manual D, or equivalent. If reasonable care and judgment is used in designing the duct system (both return and supply ducts) and the system is designed to reasonable parameters for airflow per ton, static pressure across the fan and friction rate, these systems should have no problem passing the diagnostic tests. Return ducts should not be sized according to Tables 150.0- C and D purely as a way to avoid the diagnostic testing. While undersized return ducts are very often the cause of poor airflow in many systems, they are only part of the overall system.
The following design guidelines will increase the chances of the system passing the AF/FE testing without sizing the return ducts according to Table 150.0-Cand D:
1. Right-size the HVAC system; if a 3-ton unit is enough to satisfy the cooling load, do not install a 4-ton unit “just to be safe”. Oversizing equipment can cause comfort problems in addition to excessive energy use.
2. The HVAC designer must coordinate closely with the architect and structural engineer to make sure that the ducts will fit into the home as designed.
3. Prepare a detailed mechanical plan that can be followed in the field. If deviations must occur in the field, make sure that they are coordinated with the designer and that the design is adjusted as needed.
4. Follow Manual D for duct sizing:
a. Make sure that the correct duct type is being used (vinyl flex, sheet metal, rigid fiberglass, etc.).
b. Make sure that all equivalent lengths and pressure drops are correctly accounted for (bends, plenum start collars, t-wyes, filters, grilles, registers, etc).
c. Select a furnace that will provide at least 400 cfm/ton at the desired static pressure of 125 to 150 Pa (0.5 to 0.6 inches w.c.).
d. Design the duct system to a static pressure across the fan of no more than 150 Pa (0.6 inches w.c.).
e. Consider upsizing the evaporator coil relative to the condenser to reduce the static pressure drop. This results in better airflow and slightly better capacity and efficiency. Manufacturers commonly provide performance data for such condenser coil combinations.
f. Consider specifying an air handler with a better quality fan motor.
5. Install a large grill area and use proper filter for the system; using a higher MERV filter than needed unnecessarily increases the static pressure.
6. Locate registers and equipment to make duct runs as short as possible.
7. Make all short-radius 90 Degree bends out of rigid ducting.
8. Install flex duct properly by: stretching all flex duct tight and cut off excess ducting, ensure the duct is not kinked or compressed, ensure flex duct is properly supported every four feet or less using one inch strapping having less than two inches of sag between supports.
Consider using better quality supply and filter grills. “Bar-type” registers have considerably better airflow performance than standard stamped-face” registers. Refer to manufacturer’s specifications and select accordingly.
Note that Standards Tables 150.0-C and D (Tables 4-10, 4-11, 4-12) only allow for one or two returns. There may be times where three returns are necessary on a single system.
Furthermore, Table 150.0-D does not allow for deviation from the two sizes specified. For example, the table requires two 16” return ducts for a 3.5-ton system, but specific airflow requirements and architectural constraints may dictate something more like a 20” and a 14”. In this situation, the designer would have to rely on standard engineering principles and trust their design to pass the diagnostic tests.
Having adequate room to run properly sized ducts has always been an issue. Historically, duct systems have been sized to fit into the home at the expense of proper airflow. The performance of these systems, in terms of efficiency and capacity, has suffered greatly because of this practice; it is the intent of these standards to change these practices; the home should be designed to accommodate properly sized ducts. This requires improved coordination between the architect, structural engineer, and mechanical designer earlier in the process. This is not “best practice”, this is simply good design.
It is also important to notice that the tables require that the return grilles be sized to achieve a reasonable face velocity and static pressure drop. Return grille devices must also be labeled in accordance with the requirements in section 150.0(m)12A to disclose the grille's design airflow rate and a maximum allowable clean-filter pressure drop of 12 Pa (0.05 inches water) for the air filter media.
P. Return Duct Sizing Example:
The mechanical contractor for a new home submitted the following mechanical design to the builder. It was designed using typical design specifications (400 cfm/ton at 125 Pa (0.5” wc), friction rate = 0.1, etc.). The system is has 4-ton condenser and the air handler is rated for 1600 cfm.
Figure 4-6 - Return Duct Design Option 1
Because the builder has specified a low-end air handler, he is concerned that the system may not pass the mandatory diagnostic testing requirement for airflow and fan efficacy. The builder requests that the system be re-designed with the return ducts sized according to Table 150.0-D. The following layout is the re-designed system. The only change is that the system now has two 18” return ducts and two filter grilles sized according to Table 150.0-D, rather than a single 20” return duct and a filter grilled sized according to the manufacturer’s specifications for 1600 cfm. Note that because one of the return ducts had more than one 90 degree bend, one of the bends is required to be a metal elbow (to be insulated). The two return filters are 20”x30” each and are rated by the manufacturer to show that they have a pressure drop of less than 125 Pa ( 0.5” w.c.) at 800 cfm each.
Figure 4-7 - Return Duct Design Option 2
Table 4-10 – (Standards Table 150-C): Return Duct Sizing for Single Return Duct Systems
System Nominal Capacity (Tons)
Minimum Return Duct Diameter (inch)
Minimum Total Return Filter Grille Gross Area (Inches)
Table 4-11 – (Standards Table 150-D): Return Duct Sizing for Multiple Return Duct Systems
Return 1 Minimum Duct
Return 2 Minimum Duct
Minimum Gross Filter
Grille Face Area (sq. in.)
Q. Zonally Controlled Central Forced Air Cooling Systems
§150(m)15
The primary purpose of zoning ducted air conditioners, heat pumps, and furnaces is to improve comfort. Increased comfort is attained by having the capacity of the HVAC system (cooling or heating delivered) follow the shift in load as it changes across the house. For example, it is common for two-story homes to be too hot on the second floor in both summer and winter. Zoning has the capability of diverting more of the HVAC capacity to the area with the increased load. Another common example is a home with a significant area of west-facing and east-facing windows. In the summer, the east rooms overheat in the morning and the west rooms overheat in the afternoon.
Providing the most agreeable temperature to all the zones is comfortable, but it carries with it the distinct possibility of increased energy consumption. Since the most common home is single zoned and has only one thermostat placed near the center of the house, temperatures in the rooms distant from that thermostat will vary, sometimes significantly. If zoning is added, the more distant rooms may be conditioned to a more comfortable temperature. This increased conditioning requires more energy.
It is common for zonally controlled central forced air cooling systems to produce lower airflow through the returns thus lowering the sensible efficiency of the heating or cooling equipment. There are two primary methods by which the common multi-zoned dampered system lowers airflow: additional restriction of zoning dampers and recirculation through the air conditioner from a bypass duct. To avoid this efficiency problem, zonally controlled central forced air cooling systems utilizing a single speed air conditioner must simultaneously meet the following criteria;
1. In every zonal control mode, the system shall provide airflow through the return grilles that is equal to or greater than 350 CFM per ton of nominal cooling capacity.
2. In every zonal control mode, the fan watt draw must be less than or equal to 0.58 Watts per CFM.
The airflow and fan watt draw must be HERS verified. See Reference Residential Appendix RA3.3 for the HERS verification procedures.
Zonally controlled central forced air cooling systems with multi-speed or variable speed compressors only need to be verified to meet the above 350 CFM per nominal ton and 0.58 Watts per CFM criteria with the compressor on high speed and all zones calling for cooling.
R. Zoned Systems and Airflow and Fan Efficacy Requirements
Recent studies have shown that zoned systems (multiple zones served by a single air handler with motorized zone dampers), with or without bypass dampers, usually do not meet the AF/FE requirements when less than all zones are calling. The energy penalty that results from this is greater than the benefit of having zonal control, therefore zonal control is no longer simply assumed to be a “better than minimum” condition and there are special compliance requirements for them. Note that zonal control accomplished by using multiple single-zone systems is not subject to these requirements.
There are two choices for modeling zoned systems. One is for air conditioning condensers that have single speed compressors and the other is for condensers that have “multi-speed” compressors. Two Speed and Variable Speed Compressors are considered multi-speed. Multi-speed compressors alleviate the detrimental effects of not meeting the AF/FE when less than all zones are calling and are given special consideration when used in zoned systems. They are assumed to offset the negative impacts of zoned systems and airflow and fan efficacy testing is only required to be performed in the highest speed with all zones calling, while zoned systems with single speed compressors must be tested and pass in all operating modes.
Because zoned systems, with or without bypass dampers, are less likely to meet the AF/FE requirements when less than all zones are calling, a way is provided in the performance compliance option to take this penalty and still allow use of zone dampers. Other energy features must offset the penalty. In the performance compliance software, if the system is modeled as a zoned system with a single speed compressor, the default airflow drops to 150 CFM/ton. Note that the standard house is assumed to have an airflow of 350 CFM/ton, so there is definitely a penalty unless the user specifies a value of 350 or higher. Entering a value between 150 and 350 can lessen the penalty.
It is extremely important that the energy consultant model airflow and fan efficacy values that are reasonable and obtainable, otherwise they will fail in the field and will need to be remodeled at actual values. Energy consultants should coordinate with the HVAC designer prior to registering the Certificate of Compliance.
Note: Bypass dampers may only be installed if the Certificate of Compliance specifically states that the system was modeled as having a bypass damper.
1. A home is to be built with a zoned system (2-zones) with a single speed compressor and bypass ducts. From experience, the HVAC contractor knows that it will not be possible to meet the 350 CFM/ton requirement, but 275 CFM/ton is likely.
2. The energy consultant models the system in the proposed house with 275 CFM/ton (better than default) and 0.58 W/CFM (default). Because the standard house assumes 350 CFM/ton there is an energy penalty that must be made up with other better-than-standard features, but it is not nearly as bad as it would be at the default of 150 CFM/ton.
3. Because 275 CFM/ton is better than the default of 150, it must be tested in all zonal control modes. Because the modeled fan efficacy is the default value, it
needs only to be tested with all zones calling. If a better than default value was modeled for fan efficacy it would need to be tested in all zonal control modes.
4. The home is built and the system is verified by a rater and passes at 287 CFM/ton with one zone calling, 298 CFM/ton with the other zone calling, and 372 CFM/ton with both zones calling. Note that it must still meet the mandatory requirements of 350 cfm/ton with all zones calling.
5. If this same home was to be built with a multi-speed compressor, it would only have to be tested with both zones calling whether or not it has a bypass damper, but the target airflow would be no less than 350 CFM/ton. Compliance credit can be achieved by modeling airflows greater than 350 CFM/ton and/or fan efficacies less than 0.58 watts/CFM.
Table 4-12 – Single Zone Ducted Central Forced Air Cooling Systems
Single-Zone Ducted Cooling Systems (Single Zone Off of a Single Air Handler)
Performance Compliance Option Modeled Improved Airflow
for Airflow and Fan
and/or Fan
Efficacy Airflow ≥ 350 CFM/ton,
(Airflow and Fan Efficacy
Airflow ≥350
Fan Efficacy ≤.58 W/CFM
testing not required if Return
0.58 W/CFM
Fan Efficacy ≤0.58
(Testing Performed on Highest Speed only)
System Sized to Tables 150.0- C or D, but verification of sizing is required)
Table 4-13 – Zonally Controlled Central Forced Air Cooling Systems
Zoned Ducted Cooling Systems (Multiple Zones Off of a Single Air Handler) Performance Compliance 2
Modeled Improved
Mandatory Requirements for
Airflow and/or Fan
Airflow and Fan Efficacy 1 Airflow ≥ 350 CFM/ton and Fan Efficacy ≤ 0.58 W/ CFM
Airflow ≥ 150 CFM/ton and/or Fan Efficacy ≤ 0.58 W/CFM
(For Prescriptive Compliance Method, verification is mandatory in
(Verification of better-than- default values required in
all zonal control modes. For Performance Compliance Method, verification is mandatory using highest capacity with all zones calling)
all zonal control modes. Mandatory requirement of 350 CFM/ton and 0.58 W/CFM still applies for all zones calling)
Airflow ≥ 350 CFM/ton and
Airflow ≥ 350 CFM/ton and/or Fan Efficacy ≤ 0.58
Fan Efficacy ≤ 0.58 W/ CFM
(Verification Required Only on Highest Capacity and with All Zones Calling)
(Verification of modeled improved values required only on Highest Capacity
and with All Zones Calling)
1 For the Prescriptive Compliance Method, all Mandatory Requirements for airflow and fan efficacy must
be met, and use of a bypass duct is not allowed.
For the Performance Compliance Method, all Mandatory Requirements for airflow and fan efficacy must be met,