Update app/materials_library.py

app/materials_library.py

@@ -38,6 +38,10 @@ FENESTRATION_TYPES = [
     "Door"
 ]
 
+# Surface resistances (EN ISO 6946 or ASHRAE standards)
+R_SI = 0.12  # Internal surface resistance (m²·K/W)
+R_SE = 0.04  # External surface resistance (m²·K/W)
+
 class MaterialCategory(Enum):
     INSULATION = "Insulation"
     STRUCTURAL = "Structural"
@@ -72,8 +76,11 @@ class Material:
             return "High"
 
     def get_u_value(self) -> float:
-        # Calculate U-value: λ / d (W/m²·K)
-        return self.conductivity / self.default_thickness if self.default_thickness > 0 else 0.0
+        # Calculate U-value: U = 1 / (R_si + (λ / d) + R_se) (W/m²·K)
+        if self.default_thickness > 0:
+            r_value = R_SI + (self.conductivity / self.default_thickness) + R_SE
+            return 1.0 / r_value if r_value > 0 else 0.0
+        return 0.0
 
 class GlazingMaterial:
     def __init__(self, name: str, shgc: float, u_value: float, h_o: float, category: str, is_library: bool = True):
@@ -505,13 +512,6 @@ def display_materials_tab(material_library: MaterialLibrary):
                     help="Material type classification",
                     key="material_category_input"
                 )
-                conductivity = st.number_input(
-                    "Thermal Conductivity (W/m·K)",
-                    min_value=0.01,
-                    value=form_state.get("conductivity", editor_state.get("conductivity", 0.1)),
-                    help="Heat flow ease",
-                    key="material_conductivity_input"
-                )
                 density = st.number_input(
                     "Density (kg/m³)",
                     min_value=1.0,
@@ -571,7 +571,6 @@ def display_materials_tab(material_library: MaterialLibrary):
                         st.session_state.material_form_state = {
                             "name": name,
                             "category": category,
-                            "conductivity": conductivity,
                             "density": density,
                             "specific_heat": specific_heat,
                             "default_thickness": default_thickness,
@@ -587,6 +586,8 @@ def display_materials_tab(material_library: MaterialLibrary):
                             st.error(f"Material '{name}' already exists.")
                         else:
                             try:
+                                # Use default conductivity from library or a fallback value
+                                conductivity = form_state.get("conductivity", editor_state.get("conductivity", 0.1))
                                 new_material = Material(
                                     name=name,
                                     category=MaterialCategory[category.upper().replace("-", "_")],
@@ -612,7 +613,6 @@ def display_materials_tab(material_library: MaterialLibrary):
                                     st.session_state.material_form_state = {
                                         "name": "",
                                         "category": "Insulation",
-                                        "conductivity": 0.1,
                                         "density": 1000.0,
                                         "specific_heat": 1000.0,
                                         "default_thickness": 0.1,