From the perspective of reducing Whole Life Carbon (WLC), evaluating the Upfront Carbon (UC) of building enclosure during the design stage is a critical consideration closely linked to building design and energy efficiency performance.While existing studies have analyzed material selection and opening conditions, the inherent complexity of facades—composed of numerous diverse materials and components—means sufficient quantity and specification data for UC assessment is often unavailable during the design stage.This study focuses on such "design stage" UC assessment. It organizes key points and perspectives for setting input conditions and calculation criteria, particularly classifying enclosure types based on performance requirements (wind pressure resistance, water tightness, seismic resistance, energy efficiency, etc.) in Japan. Through parametric analysis, it identifies the impact on UC emissions.Using these results, we proposed a concept for a " composite emission intensity " per enclosure area, combining multiple materials intended for use in "design stage" UC assessment by enclosure type, along with specific examples.