ASHRAE 90.1-2016 Appendix G

Performance modelling beyond the code minimum

Appendix G is the performance route for rating programs, LEED, beyond-code targets and stretch goals. Compare your building against a computed baseline and report a Performance Cost Index that says how far past compliance you are.

Baseline generated from your proposed model per Table G3.1

Four-orientation baseline simulation, averaged

Performance Cost Index for LEED and rating programs

End-use cost tables and G3.1 rule documentation

Ratings, LEED, and stretch targets

Built for reliability & speed

Appendix G is the Performance Rating Method for ASHRAE 90.1-2016, and it does something the other paths do not: it gives you a number that says how far past code you are. You build a proposed model of your actual design, generate a baseline model using Table G3.1's rules, run both a full year, and report the Performance Cost Index. LEED, WELL, jurisdictional stretch codes and voluntary rating programs all use PCI. It is more work than ECB, and the extra work is the point.

Baseline Building

The Appendix G baseline is generated from your proposed model using Table G3.1 rules. Orientation is rotated in four cardinal directions and averaged, envelope drops back to prescriptive minimums, and HVAC is set by system type table.

Climate Zone Weather

Both baseline and proposed run on the same climate zone weather data. TMY3 for the site or an ASHRAE-provided equivalent, applied identically.

Performance Cost Index

PCI is proposed cost divided by baseline cost. A PCI below 1.0 means better than baseline. LEED, WELL and many jurisdictions set target PCI thresholds well below that.

Glazing as Designed

Proposed glazing is modelled exactly as specified. Baseline is capped at 40 percent WWR regardless of what you actually built, which is where large facades pick up their margin.

Shading and Site

Real shading and site context in the proposed model. Baseline has no external shading, no site context, and cardinal-averaged orientation.

System Type Baseline

Table G3.1.1-3 sets the baseline HVAC system by building type and area. Get it wrong and every downstream comparison is against the wrong reference, so this table gets checked twice.

Unregulated Loads

Plug loads, process energy and receptacle loads are identical between baseline and proposed. They still show up in the cost totals, which is why total-building PCI is not the same as regulated-load PCI.

Four-Orientation Runs

Baseline is simulated in all four cardinal orientations and averaged. Proposed is run in its actual orientation once. That is four extra simulations you cannot skip.

PCI Report

Full end-use cost tables for both models, PCI calculation, baseline system justification, and documentation of every G3.1 rule applied. LEED and jurisdiction reviewers will want the lot.