How Energy Codes Work
Understanding prescriptive requirements and their evolution across code cycles
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Section 2 of 5Prescriptive vs Performance Pathways
Energy codes regulate buildings through two primary mechanisms: prescriptive requirements that specify exact component characteristics (R-values, U-factors, equipment efficiencies), and performance pathways that set whole-building energy targets with flexibility in how to achieve them. The International Energy Conservation Code (IECC) and ASHRAE 90.1 update every 3 years, progressively tightening requirements as technology improves and costs decline.
đ Prescriptive Path
- âSpecific component requirements (insulation R-values, window U-factors)
- âClimate zone adjustments (7 zones based on heating/cooling degree days)
- âSimple compliance verification via plan review
- â Less design flexibility, may miss optimization opportunities
⥠Performance Path
- âWhole-building energy budget via simulation (EnergyPlus, eQUEST)
- âDesign flexibility - trade-offs between envelope, systems, renewables
- âCan achieve 10-30% better performance than prescriptive baseline
- â Requires energy modeling expertise, more complex documentation
Interactive Code Requirements Explorer
Compare IECC requirements across code cycles, building types, and climate zones
Commercial Requirements
Wall Insulation
R-20
Window U-Factor
0.36
Lighting Power Density
0.63 W/sf
Economizer Required
Yes
Free cooling via outside air
âšī¸
Understanding Requirements
- âĸ R-Value: Thermal resistance - higher numbers mean better insulation
- âĸ U-Factor: Heat transfer rate - lower numbers mean better performance
- âĸ ACH50: Air changes per hour at 50 pascals pressure - lower is tighter
- âĸ LPD (W/sf): Lighting power density per square foot - lower is more efficient
Explore Compliance Strategies
Learn how projects demonstrate code compliance