Guideline 36-2021: What’s New and Why It’s Important

From ASHRAE Journal Newsletter, September 14, 2021

Custom control sequences for HVAC systems are often dumbed down, limiting their potential to reduce a building’s energy use. To help maximize energy efficiency and performance, ASHRAE Guideline 36, High-Performance Sequences of Operation for HVAC Systems, includes uniform sequences of operation for HVAC systems, which help provide control stability and allow for real-time fault detection and diagnostics.

The recently released 2021 version of ASHRAE Guideline 36 includes 24 addenda developed over the last three years. A few of the updates include:

• Additional applications such as fan-coil units and central hot water and chilled water plants. The previous version addressed only variable air volume (VAV) air-handling systems and terminal units.
• Enhanced sequences to existing sections, such as an addendum that provides automatic and dynamic calculation of VAV box minimum airflow setpoints.
• Bug fixes to existing sections.  “The sequences are necessarily complex in order to meet the goal of optimum energy efficiency while meeting ventilation and comfort standards. Accordingly, the guideline project committee (GPC) and other users of the guideline found bugs or other shortcomings in the 2018 logic that needed to be fixed,” said Steve Taylor, P.E., Fellow/Life Member ASHRAE, former chair of Guideline 36’s project committee.

What Guideline 36 Does and Its Challenges

Standardized advanced control sequences—such as those in Guideline 36—help reduce engineering time, programming and commissioning time and energy consumption. They also improve indoor air quality (IAQ) and facilitate communication among specifiers, contractors and operators by providing a common set of terms.

The standard practice for HVAC digital control systems includes creating custom control sequences for each building, said Taylor. These custom control sequences are often dumbed down to “keep it simple” for the building operator to the extent that they are often not in compliance with codes and standards such as ANSI/ASHRAE/IES Standard 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings, and ANSI/ASHRAE Standard 62.1, Ventilation for Acceptable Indoor Air Quality.

These oversimplified sequences are not always well programmed, debugged and commissioned because of their one-off custom applications, resulting in subpar building performance. Guideline 36 was created to address these issues, including best-in-class control sequences that have been optimized to minimize energy use and maximize comfort and IAQ. The sequences are intended to be preprogrammed and pre-debugged by control system manufacturers.

Early implementations of the sequences have shown dramatic energy savings—including a reduction of more than 50% in boiler energy use in two buildings—while maintaining code minimum ventilation requirements, improving thermal comfort and reducing costs.

Although most people recognize the value in standardized high-performance control sequences, the primary challenge with this guideline is “getting the ball rolling” with implementation of its sequences, said Taylor, who added that the guideline benefits everyone in the building design and construction process, including the owner, by reducing everyone’s costs while improving performance.

“But there is a bit of a ‘chicken-and-egg’ issue: Engineers are reluctant to specify the sequences because they are complex, and they don’t want the costs for programming and commissioning to be a cost burden on their projects,” he said. “And control contractors will not implement Guideline 36 sequences unless they are specified.”

Another challenge, Taylor said, is that manufacturers are reluctant to implement sequences until dealers demand them.

“We have identified the best way to break this cycle is to convince the manufacturers to preemptively do the programming for their dealers now without waiting for them to request it. This is the most efficient approach: The sequences are programmed only once for each manufacturer, not multiple times by their dealers, reducing costs and improving quality control,” he said. 

ASHRAE Journal articles and research by national laboratories and others demonstrating how well Guideline 36’s sequences work have increased the popularity of the sequences, helping to convince manufacturers. To date, seven major control system manufacturers have preprogrammed at least the most commonly used Guideline 36 sequences for their dealers. 

“Engineers can now specify those manufacturers on their projects knowing that programming and commissioning costs should be reduced, not increased,” Taylor said.

What’s Next for Guideline 36?

“Eventually, Guideline 36 is intended to address all common air and hydronic distribution systems, not just VAV,” he said. “Sequences for more applications will continue to be developed. The Guideline is under continuous maintenance for this reason.”

Since the guideline debuted in 2018, Taylor and others have led many seminars and webinars—including an introduction to the current version of Guideline 36. A common question asked at those seminars is about what sequences are not yet included and when they might be added, said Taylor.  

“Primarily people asked about hydronic systems, such as hot water and chilled water plants, which have now been added with sequences based on ASHRAE Research Project RP-1711, Advanced Sequences of Operation for HVAC Systems—Phase II Central Plants and Hydronic Systems,” said Taylor.

Others have asked about various zonal systems (e.g., radiant, chilled beams) and dedicated outdoor air systems (DOAS), said Taylor. Although those systems are not yet part of Guideline 36, the committee expects to cover them in the 2024 version based on ASHRAE RP-1865, Optimizing Supply Air Temperature Control for Dedicated Outdoor Air Systems, which is developing optimized supply air temperature reset logic for DOAS.