Updates to ASHRAE 90.1

An update of ASHRAE Standard 90.1 looks at building envelope, HVAC, plumbing, lighting, and elevators and escalators. The bulk of the article will focus on the 2013 edition, with a look at 2016 addenda that are already approved.
By J. Boldt, L. Sciarra, M. Rosenberg, and E. Richman January 29, 2016

This article is peer-reviewed.Learning objectives:

  • List changes to ASHRAE 90.1, both the 2010 and 2013 editions.
  • Preview the approved changes in ASHRAE 90.1-2016.
  • Explain the approved and other significant in-process addenda in all disciplines since the 2013 edition was published. 

ASHRAE Standard 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings continues to evolve and increase energy savings in buildings (see Figure 1). Some states enforce older codes, such as the 2009 International Energy Conservation Code (IECC) and ASHRAE 90.1-2007, while others have updated to 2012 IECC/ASHRAE 90.1-2010, and a few states have adopted 2015 IECC/ASHRAE 90.1-2013. (The article "What’s new in ASHRAE 90.1-2013" in the January 2014 issue of Consulting-Specifying Engineer covered the 2013 changes, not including lighting.)

Figure 1: This shows the progression of energy savings in ASHRAE Standard 90.1. Since 1975, the ASHRAE 90.1 standard has continued to evolve and increase energy savings in buildings. The latest edition, 2013, prescribes an energy-use baseline that is abou

One major change that affects both envelope and mechanical systems is that the climate zones were updated to match those in the 2013 edition ASHRAE Standard 169: Climatic Data for Building Design. For example, this moved the southern half of Wisconsin from climate zone 6 to climate zone 5, reflecting warming trends in the weather data and realigning of political and geographic borders to more accurately reflect the weather data. This also added climate zone 0, because there are places in the world that are much hotter than areas like Miami, which is in climate zone 1.

Building envelope 2013 changes

Insulation values for wall and window U-factor and solar heat gain coefficient (SHGC) were made more stringent. The window-to-wall-ratio requirement, however, remained the same at 40%. Note, the window-to-wall ratio in 2012 IECC is 30%.

The standard expanded the areas where daylighting (called toplighting) is required in several large space types, and modified the way the window orientation/area provisions are calculated. The other change is that the envelope-only trade-off option rules were updated so one can use current whole-building energy simulation software.

Building envelope 2016 changes

Of the many "in process" addendums, three stand out. First, minimum heating and cooling capacities that make a space fall into the "heated" or "cooled" categories were reduced. Second, changes were made to the fenestration U-factor and SHGC, with some additional modifications made to the fenestration orientation provisions as well. And third, a new section was added that begins to address air-leakage inspections. While the performance requirements have not changed, the standard will clarify that an inspection and verification program must be documented.

HVAC, plumbing 2013 changes

The reheat limitations were modified in the 2013 edition to require a reduction in flow to 20% in deadband, and were relaxed to allow up to 50% flow at peak heating. This increases energy efficiency in deadband (assuming that ASHRAE Standard 62.1 is satisfied) and lowers first cost, but increases energy use at times when peak heating is needed.

Direct digital control (DDC) requirements were added. These require DDC for most new building air-handling systems, chilled-water, and heating plants. A table details criteria that require DDC for new buildings, alterations, and additions.

HVAC, plumbing 2016 changes

In the 2016 edition, hotels/motels with more than 50 guest rooms are required to have automatic controls for each guest room that raise the cooling and lower the heating setpoint temperature by 4°F within 30 minutes of all occupants leaving the room. When unrented, the setpoint shall be ≥80°F in cooling and ≤60°F in heating. Networked rooms are permitted to return to occupied temperatures 60 minutes prior to expected occupancy.

In this edition, ≥1/12- to 1-hp electric motors now have minimum efficiency requirements that push the industry toward 3-phase or electronically commutated motors (ECM). In many of these applications, ECMs are becoming more popular because of the wide speed variation compared to small, 3-speed permanent-split capacitor (PSC) motors.

Significant increases were made to minimum efficiencies for variable refrigerant flow (VRF) systems.

Vestibule heating is prohibited when the outside air temperature is above 45°F. The cooling setpoint shall not be below 85°F, and the heating setpoint shall not be above 60°F.

Variable flow is required for hydronic systems with three or more control valves. Variable speed control is required for pumps with motors larger than 5 hp. One of two control methods is required:

  • Differential pressure control that senses pressure near the critical heat exchanger plus reset of the differential setpoint based on valve position
  • Chilled- or heated-water temperature reset based on valve positions.

Duct-sealing requirements were clarified to avoid confusion with examples in the Sheet Metal and Air Conditioning Contractors’ National Association (SMACNA) HVAC Air Duct Leakage Test Manual.

The fan-power credit for fully ducted systems was revised to only give credit to systems required by code or accreditation standards to be fully ducted. This removes the credit from systems such as ducted return systems in office buildings that could use return-air plenums.

The wording of the fan-power allowance for heat-recovery systems was modified to clarify the order of the calculation steps.

Lighting section 2010 changes

The 2010 version of Standard 90.1 currently is the basis for the building energy-code requirements in many states. For lighting, the requirements cover the two main categories of lighting power density (LPD) limits and controls. Each must be separately complied with to ensure effective energy savings that is a combination of just the wattage needed to provide effective light and controls to turn it off when not needed.

The LPD-limit requirement for a building specifies the total amount of power that can be used to light the building. These total limits are prescribed separately for both interior and exterior parts of the facility. For interior areas, there are two possible prescriptive compliance options. The building-area method provides one total lighting power limit for the entire interior of the building. The space-by-space method provides separate limits for each different space type, and the total limit for the building is calculated as the sum of the individual allowances based on the size of each space. In either case, the total limit for the building is the value used for building compliance.

For exterior compliance, only an individual area (space) compliance method is provided. This method is applied in a similar manner as the interior space-by-space method, with the total exterior limit being the sum of the individual exterior area limits. It is useful to clarify that for both interior and exterior applications, it is the total allowance that is used to determine compliance with the standard and not the individual space allowances. This means that the standard does not care how much of the total power is used in each space or area as long as the total for the interior of the building does not exceed its total interior limit and the total for the exterior does not exceed the total exterior limit.

It is also important to note that there are many exceptions to the types of lighting that must be included as part of compliance with the standard. In the 2010 edition of the standard, there are 18 different lighting applications that do not have to be counted toward the interior LPD limits. These typically are specific nongeneral lighting applications, such as for theatrical stage performance, plant growth, and exit signs. There also are 12 exterior lighting applications that do not have to be counted for compliance, including lighting for industrial production, searchlights, theme elements in amusement parks, and directional signage.

The control requirements in 2010 specify which controls must be applied to the various space types or applications within a building or similarly to exterior spaces or applications. The primary control requirement for all interior lighting is automatic shutoff of general and task lighting when not needed. This can be accomplished with either a schedule for after-hours shutoff or occupancy-based sensors that turn off lights when the space is empty. Some spaces are also further required to have the specific occupancy-based sensor shutoff of general lighting. This includes classroom, conference, lunch, storage, copy/print, individual office, restroom, and locker room-type spaces.

All spaces, with some exceptions, are also required to provide the occupant with the ability to turn off at least 30% of the space lighting when not needed. The control of electric lighting when sufficient daylight exists in a space also is required. This requirement has minimum area requirements before the control is required, such as 250 sq ft for sidelighting applications (windows) and 900 sq ft for overhead daylighting applications (skylights).

Another control requirement for the interior of buildings applies specifically to indoor parking garage areas. This set of requirements includes daylighting control (where applicable), zone lighting power reduction based on detected occupancy, and allowances for daylight-transition zones for entries and exits from the garage. A final set of requirements lists seven specific applications where control of that lighting must be separate from general lighting or have additional specific requirements. These specific applications include guestrooms, display and case lighting, task lighting, stairwells, nonvisual, and demonstration lighting.

The control requirements for exterior applications start with automatic shutoff of lighting when there is sufficient daylight. This would typically be the standard photocell control used on many parking and streetlights. The requirements also include shutoff of facade and landscape lighting before and after business hours. The remaining exterior lighting is required to be turned down by at least 30% either after hours or when no occupancy is detected. Additional requirements in the standard include specific procedures for the functional testing of lighting controls to ensure that the lights will effectively capture expected energy savings as well as requirements for manuals and drawings of installed lighting systems to be provided to building operators.

Figure 2: Exterior-lighting power limits depend on location zones. For ASHRAE Standard 90.1 and the IECC, the external-lighting power limits have been categorized by exterior location. The categorizations have been developed to try to match commonly underLighting section 2013 changes

The 2013 version of Standard 90.1 saw several clarification changes and some major updates with significant energy-savings potential.

The lighting control requirements were significantly increased by adding controls and applying the existing control requirements to a wider list of space types. This change was implemented with a revised and expanded LPD-limit table that now includes the applicable control requirements by space type. The added controls included occupancy-based partial automatic-on and partial automatic-off. The partial automatic-on requirement specifies that only 50% of the general lighting can be automatically turned on based on sensing occupants in the space. The remaining lighting must be activated directly by occupant choice. The partial automatic-off ensures that at least 50% of the general lighting in the space is turned off when no occupants are in the space. This is applied to spaces where full automatic-off may be a safety issue or a building-function issue such as in corridors, library stacks, and lobbies.

Changes also were made to the interior LPD limits based on the publication of the new edition of the Illuminating Engineering Society (IES) Lighting Handbook. The models used to determine the LPD values in ASHRAE 90.1 are based on the task-lighting-level recommendations provided by IES. When a new version of the handbook comes out, some recommendations change, and these are typically then incorporated into the Standard 90.1 space-type models, which change the LPD limit. In this case, many space-type LPD values went down, some did not change, and a few went up. These changes also caused some of the whole-building LPD values to drop.

A change to the alterations section added specific control requirements. For this version of the standard, any interior lighting alteration that requires compliance with the LPD limits also must comply with the basic after-hours automatic shutoff. Exterior applications must also comply with the shutoff when sufficient daylight is available and after-hours façade and landscape lighting shut off.

Lighting section 2016 changes

Many changes for lighting requirements are working their way through the process. Several could be considered clarification while others will have significant impact on construction practice as well as energy savings.

One important change that has already been approved as part of the supplement to the 2013 edition of Standard 90.1 is an increase in the lighting control requirements for alteration projects. Previously, only automatic shutoff based on a schedule or occupancy sensing was required. The new requirements call for most of the same controls that are currently required for new construction. These include occupancy-based control and bi-level control in most spaces, but excludes the daylighting controls required for new construction. The inclusion of these new control requirements will increase the work required to comply with applicable energy codes for alterations in many spaces, but is expected to be more than offset by additional energy savings from the controls.

The daylighting controls required for new construction are not included for alteration projects in the 2016 version. The complexities of this control type are still considered unduly cumbersome for many alteration situations. There is also an exception for simple alteration projects that are just retrofits involving changing only lamp and ballast combinations within fixtures. For these simple retrofits, compliance only with the LPD limits is required and no additional controls need to be added.

A significant change that is working its way through the system to become part of the 2016 edition is a modification of the interior and exterior LPD limits. These changes are based on the introduction of LED lighting as a major basis for the determination of the LPD limits. LED technology has been steadily making its way into the mainstream commercial markets for many years. The promise of increased energy savings with LED lighting was a driver in considering it for inclusion in the 2013 version of the standard; but at the time, there was still much concern about availability and variability of products. With 3 additional years of LED technology and product development, there are now plenty of good products available to provide complete confidence that LED technology can be successfully used as a basis for reducing energy use in buildings.

Another proposed change will require occupancy-based lighting control in outdoor parking areas. This requirement will only apply to shorter (24-ft or less) poles with significant lighting-fixture wattage (78 W or more) and only require 50% power reduction when no activity in the area of the pole is detected.

In the interest of simplicity, another set of additions to the standard adds 1 page—simplified compliance paths for office, retail, and school facilities. These alternate compliance methods offer users with more simplified and/or smaller facilities an easier way to comply without working through the entire lighting section to determine applicable compliance items. Compliance requirements may be a little tighter with these methods; but for simpler or smaller buildings, these should be easy to comply with and require much less documentation and plan evaluation.

Another change that is in process and likely to be included in the 2016 version of the standard involves voltage-drop limits. This clarification notes that the maximum allowed voltage drop for a building’s electrical system is 5% for combined feeder and branch electrical systems instead of separate values.

Figure 3: The lighting section of ASHRAE Standard 90.1 specifies which lighting controls must be applied to the various space types or applications within a building or similarly to exterior spaces or applications. The control requirements for exterior apElevators and escalators

In ASHRAE 90.1-2010, requirements were added for lighting and ventilation-fan efficiency and for shutoff of lighting and ventilation after 15 minutes of no activity. In ASHRAE 90.1-2013, escalator and fast-walk speed control were added to reduce energy use when unused. It is possible, but perhaps not likely, that ASHRAE 90.1-2016 will add elevator movement efficiency requirements. An ISO standard has been approved and the only thing delaying code approval is elevator industry adoption and rating of the available products.

Performance rating method 2016 changes

Addendum bm makes two major changes to Appendix G for 2016. First, it allows Appendix G to be used as a path for compliance with the standard in addition to rating "beyond code" performance of buildings. This prevents modelers from having to develop separate building models for code compliance and beyond code programs. Using this new version of Appendix G to show compliance with the 2016 version of the standard, the proposed building design needs to have a performance-cost index (PCI) less than targets shown in a new table based on building type and climate zone.

The second change is that the baseline design is now fixed at a stable level of performance set approximately equal to the 2004 edition. The stringency of the baseline will not change with subsequent versions of the standard. Instead, compliance with new versions of the standard will simply require a reduced PCI (a PCI of 0 is a net zero building). Using this approach, buildings of any era can be rated using the same method. The intent is that any building energy code or beyond code program can use this methodology and merely set the appropriate PCI for their needs. The multiple uses and stable baseline will encourage the development of software tools that automate creation of the baseline building, as the market will be larger and the useful life of the software is extended.

This path should eventually replace the Chapter 11 performance method because it gives credit for design choices that were previously not credited, such as optimized window-to-wall ratio, right-sizing of HVAC equipment, optimized building orientation, and using HVAC system types that are more efficient (instead of always comparing performance against a model building with the same HVAC system).

ASHRAE Standard 90.1 continues to push the limits of economical energy conservation. The standard is required to meet lifecycle cost limits for all proposals. A designer who is looking for energy savings can be confident that a 2013 or 2016 addendum that passed or even was issued for public review is economical. Designers should start with the items approved in newer versions of Standard 90.1 when suggesting energy-reduction measures to their clients.


Jeff Boldt is a principal and director of engineering for KJWW Engineering Consultants and a voting member of the ASHRAE 90.1 Committee, its mechanical subcommittee, and ASHRAE 189.1.

Leonard Sciarra is a senior associate, project architect, technical director, and sustainability leader with Gensler; he currently serves as chair of the ASHRAE 90.1 envelope subcommittee and is past chair of the Chicago chapter of the AIA Committee on the Environment.

Michael Rosenberg, senior research scientist at Pacific Northwest National Laboratory, has worked in the building energy field for more than 20 years upgrading building energy codes, training code officials and design professionals, designing high-performance buildings, analyzing complex building systems, and developing and administering beyond-code energy programs.

Eric Richman, senior research engineer at Pacific Northwest National Laboratory, is currently the chairman of the ASHRAE 90.1 lighting subcommittee and has been involved in the standard’s development since 1995.