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.


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.

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