Codes and standards report
Abstract
The goal of this study was to (1) propose changes to Title 24 to support improved modeling capabilities and help achieve significant energy efficiency goals for radiant systems in California, and (2) propose changes, as needed, to relevant ASHRAE Standards, Handbooks, and Guidelines to provide new information and guidance on radiant systems. The current version of California Building Energy Efficiency Standards, Part 6 of the California Building Standards Code (Title 24) does not address factors specific to high thermal mass radiant systems within the body of the Standards. The alternative compliance method references some limited aspects relating to radiant systems but it is incomplete and not practically applicable, and has not yet been implemented in the associated compliance software. In addition, there are some modeling limitations for radiant systems in EnergyPlus, which is the simulation engine underlying the compliance software for the Title 24 performance approach. Updates to the Title 24 alternative compliance method are needed to ensure that modeled performance accurately reflects proposed designs, and to properly allow buildings with radiant systems to take appropriate credit for their performance. This study provided a background and roadmap of the steps needed to provide effective coverage of radiant systems for Title 24 compliance. Listed below are topics that are recommended to be added to the ASHRAE Standards and Handbooks.
• Provide consistent definitions for different radiant system types in ASHRAE Handbook System and Equipment, Chapter 6 (Radiant Heating and Cooling).
• Provide comfort data in real radiant buildings in ASHRAE Handbook System and Equipment, Chapter 6 (Radiant Heating and Cooling).
• Provide revised cooling load definitions and calculations in ASHRAE Handbook Fundamentals, Chapter 18 (Nonresidential Cooling and Heating Load Calculations) and ASHRAE Handbook Fundamentals, Chapter 19 (Energy Estimating and Modeling Methods).
• Provide revisions to account for effect of night cooling for buildings conditioned by radiant system in ASHRAE Handbook Fundamentals, Chapter 18 (Nonresidential Cooling and Heating Load Calculations), ASHRAE Handbook Fundamentals, Chapter 19 (Energy Estimating and Modeling Methods), ASHRAE Guideline 36-2018 (High-Performance Sequences of Operation for HVAC Systems), and ASHRAE Handbook Systems & Equipment, Chapter 6 (Radiant Heating and Cooling).
• Provide new design guidance to account for the impacts of direct solar radiation on chilled radiant floors in ASHRAE Handbook Applications, Chapter 54 (Radiant Heating and Cooling), and ASHRAE Handbook System and Equipment, Chapter 6 (Radiant Heating and Cooling).
• Provide new design guidance to account for the impacts of acoustical ceiling panels and clouds on cooling capacity of radiant ceiling slabs in ASHRAE Handbook System and Equipment, Chapter 6 (Radiant Heating and Cooling).
• Provide new design guidance to account for the impacts of air movement from ceiling and other fans on cooling capacity for both radiant ceilings and floors in ASHRAE Handbook System and Equipment, Chapter 6 (Radiant Heating and Cooling).