Current HI doesn't cover extreme conditions, propose to improve with extended heat index

[yujiex]

Issue overview

The heat index reflects human perceived hotness considering both temperature and humidity. The current heat index calculation in EnergyPlus is based on Steadman’s method, which gives nonphysical results in extreme weather conditions. The extended heat index fixes this issue and outputs a more realistic heat index. It can also be associated with the health outcomes (heat stroke, etc.) of an idealized human, helpful in the quantification of damages from extreme weather.

The implementation is based on code on this page

Details

Some additional details for this issue (if relevant):

• Platform (Operating system, version)
• Version of EnergyPlus (if using an intermediate build, include SHA)
• Unmethours link or helpdesk ticket number

Checklist

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• Defect file added (list location of defect file here)
• Ticket added to Pivotal for defect (development team task)
• Pull request created (the pull request will have additional tasks related to reviewing changes that fix this defect)