ASHRAE 90.1-2019 (I-P)

Standard 90.1 has been a benchmark for commercial building energy codes in the United States and a key basis for codes and standards around the world for more than 35 years. This standard provides the minimum requirements for energy-efficient design of most buildings, except low-rise residential buildings. It offers, in detail, the minimum energy efficiency requirements for design and construction of new buildings and their systems, new portions of buildings and their systems, and new systems and equipment in existing buildings, as well as criteria for determining compliance with these requirements. It is an indispensable reference for engineers and other professionals involved in design of buildings and building systems.

The 2019 edition includes various modifications and clarifications to improve internal consistency and to standardize the structure and language of the document.
Significant changes to requirements include the following

Administration and Enforcement
• New commissioning requirements in accordance with ASHRAE/IES Standard 202
Building Envelope
• Combined categories of “nonmetal framed” and “metal framed” products for vertical fenestration
• Upgraded minimum criteria for SHGC and U-factor across all climate zones
• Revised air leakage section to clarify compliance
• Refined exceptions related to vestibules, added new option and associated criteria for using air curtains
Lighting
• Modified lighting power allowances for Space-by-Space Method and the Building Area Method
• New simplified method for lighting for contractors and designers of renovated office buildings and retail buildings up to 25,000 ft2 (2300 m2).
• Updated lighting control requirements for parking garages to account for the use of LEDs
• Updated daylight responsive requirements, added definition for “continuous dimming” based on NEMA LSD-64-2014
• Clarified side-lighting requirements and associated exceptions
Mechanical
• New requirements to allow the option of using ASHRAE Standard 90.4 instead of ASHRAE Standard 90.1 in computer rooms that have an IT equipment load larger than 10 kW
• Added pump definitions, requirements, and efficiency tables to the standard for the first time
• New equipment efficiency requirement tables and changes to existing tables
• Replaced fan efficiency grade (FEG) efficiency metric with fan energy index (FEI)
• New requirements for reporting fan power for ceiling fans and updated requirements for fan motor selections to increase design options for load-matching variable-speed fan applications
• New energy recovery requirements for high-rise residential building
• New requirement for condenser heat recovery for acute care inpatient hospitals
Energy Cost Budget (ECB) Method (Section 11)
• Numerous changes to ensure continuity
• Set baseline for on-site electricity generation systems
Performance Rating Method (Appendix G)
• Clarified Appendix G rules and corresponding baseline efficiency requirement when combining multiple thermal zones into a single thermal block
• New explicit heating and cooling COPs without fan for baseline packaged cooling equipment
• New rules for modeling impact of automatic receptacle controls
• Set more specific baseline rules for infiltration modeling
• Clarified how plant and coil sizing should be performed
• Updated building performance factors
Both Compliance Paths
• Clearer, more specific rules for treatment of renewables
• New updates to rules for lighting modeling