Compliance is not only a final calculation
Part L outcomes reflect fabric and building-services decisions made throughout design. The compliance route and information responsibilities should be established early.
System efficiency must match operation
Heating, cooling, ventilation, lighting and controls need realistic zoning, schedules and performance assumptions rather than nominal product efficiencies alone.
Architecture and MEP inputs interact
Glazing, shading, air permeability, thermal bridging and space use influence loads and system performance. Changes in one discipline should be reflected in the assessment model.
Completion evidence needs planning
Commissioning, controls information, product data and as-built changes should be tracked during delivery so the final evidence is consistent with the completed building.