The PA Uniform Construction Code references two primary ICC codes for residential energy efficiency: 2018 IRC and 2018 IECC.
The energy provisions in these two codes are nearly identical. They can be used interchangably for compliance.
The 2018 IECC and IRC were not adopted in their entirety. The Rules and Regulations released by the PA Department of Labor and Industry include a number of additions, deletions, and modifications. It would be useful for PA construction professionals if the state would release modified versions of these codes that incorporate all of the changes, like NY has done. However, no such all-in-one PA-specific codes exist, so it is left to professionals to pore through the various documents to understands the details.
Some of the amendments reference versions of the IECC from two other years: 2009 and 2015. Professionals may find it useful to have access to them:
The IECC and IRC provide various options for compliance. These include simple prescriptive tables listing insulation levels, as well as flexible pathways that allow builders to tradeoff improved performance in one area (e.g. ceiling insulation) for reduced performance in another area (e.g. wall insulation).
The Department of Labor and Industry worked with the PA Housing Research Center at Penn State to create one additional pathway that allows builders to meet less stringent envelope requirements if they select one "Energy Enhancement" from a table of options. This is detailed in a document called "2021 Pennsylvania Alternative Residential Energy Provisions:
