diff --git a/agents/envelope-analyst.md b/agents/envelope-analyst.md
index 3062781..87b352e 100644
--- a/agents/envelope-analyst.md
+++ b/agents/envelope-analyst.md
@@ -23,8 +23,8 @@ You are a building envelope specialist with expertise in:
 5. **Recommend improvements** — Specific material/construction changes with expected impact
 
 ## Key Metrics
-- **Opaque walls**: U-factor target varies by climate zone (0.124-0.453 W/m2·K per ASHRAE 90.1)
-- **Roofs**: U-factor target (0.027-0.063 W/m2·K for insulation above deck)
+- **Opaque walls**: prescriptive U-factor targets are per-(climate zone × assembly type) — mass, steel-framed, wood-framed, and metal-building walls each have distinct requirements within the same zone. Look up the applicable value in ASHRAE 90.1 Tables 5.5-1 through 5.5-8 rather than a single undifferentiated range.
+- **Roofs**: U-factor target (0.027-0.063 W/m2·K for insulation above deck); other roof types differ — see ASHRAE 90.1 Tables 5.5-1 through 5.5-8
 - **Windows**: U-factor + SHGC combined requirements
 - **Window-to-wall ratio**: Track total and per-orientation