replace Behind the Intent, Beta Update text with the following:
The ASHRAE standards have been updated to the latest versions:
ASHRAE 55-2010 ASHRAE 55-2017 (updated version)
o Major changes from 2010 include: clarifications to elevated air speed method, new requirement to calculate the change to thermal comfort resulting from direct solar radiation impacting occupants.
ASHRAE Applications Handbook 2011 edition ASHRAE Applications Handbook 2015 edition (updated version)
Option 2 is available for use through regional compliance pathways.
Under Step-by-Step Guidance, replace with the following:
Step 1. Select Analysis Method(s)
Select the methodology from ASHRAE Standard 55-2017 that will be used for the thermal comfort analysis. Refer to the standard for restrictions with some of the methods. For example, section 5.3.1 is restricted to conditions without direct solar radiation.
Additional calculations or considerations required if direct-beam solar radiation falls on the occupant. Calculations are available in ASHRAE 55-2017 Normative Appendix C.
Tools such as the CBE Thermal Comfort Tool (
https://comfort.cbe.berkeley.edu/) may be used to assist with the analysis. A new feature (SolarCal) is also available for the direct-beam solar radiation calculations.
Step 2. Design Project’s Conditioning Systems
Design the project’s conditioning systems to provide the acceptable comfort conditions identified in the analysis. Verify that all spaces at risk for discomfort, such as locations close to the entrances prone to drafts or west-facing walls that may retain heat, have been addressed.
ASHRAE 55–2017, Section 6.1, requires the design to be within the acceptable comfort range at all combinations of conditions that are expected to occur, including variations in internal loads and the exterior environment, and at both full- and partial-load conditions. Systems that cannot maintain comfort under all conditions (e.g., a constant-volume rooftop unit with a single compressor may have problems controlling humidity levels) do not meet the credit requirements.
Under Required Documentation, replace with the following:
Refer to LEED v4 ref guide with the following modifications:
For thermal comfort design compliance, supporting documentation verifying that the thermally conditioned spaces meet ASHRAE Standard 55-2017 for 80% acceptability. Examples include a psychometric chart, PMV/PPD calculations, CBE Thermal Comfort Tool results, a copy of ASHRAE Standard 55-2017 Figure I2, Figure I4, and/or Figure I5, or predicted worst case (both heating and cooling) indoor conditions for each month on a copy of ASHRAE Standard 55-2017 Figure 5.4.2.
Explanation of how project complies with the direct solar radiation requirements in ASHRAE Standard 55-2017.
o Screenshots of the local discomfort assessment and SolarCal windows from the CBE Thermal Comfort Tool are acceptable.
