diff --git a/rhino/elemente.py b/rhino/elemente.py
index 28d469c..1d1a1f3 100644
--- a/rhino/elemente.py
+++ b/rhino/elemente.py
@@ -4005,18 +4005,24 @@ def _regenerate_element_body(doc, element_id, src_obj, meta, geom, geschoss_name
             cutouts.append(cutout)
             opening_jobs.append((op_meta, eff_pt, uk))
         if cutouts:
+            # Performance: alle Cutouts in EINEM BooleanDifference-Call pro
+            # Schicht subtrahieren (statt N Einzel-Diffs). Bei 3-schichtiger
+            # Wand mit 2 Oeffnungen reduziert das 6 BoolDiff-Ops auf 3.
+            # Toleranz fix 0.001 m = 1 mm. Architektur-Genauigkeit reicht das,
+            # und Boolean-Diff laeuft mit groesserer Toleranz spuerbar schneller
+            # als mit z.B. 0.0001.
+            tol = 0.001
             new_layer_breps = []
             for (brep, color, lname) in layer_breps:
                 if brep is None:
                     new_layer_breps.append((None, color, lname)); continue
-                for cut in cutouts:
-                    try:
-                        diff = rg.Brep.CreateBooleanDifference(
-                            [brep], [cut], 0.001)
-                        if diff and len(diff) > 0:
-                            brep = diff[0]
-                    except Exception as ex:
-                        print("[ELEMENTE] BoolDiff layer:", ex)
+                try:
+                    diff = rg.Brep.CreateBooleanDifference(
+                        [brep], cutouts, tol)
+                    if diff and len(diff) > 0:
+                        brep = diff[0]
+                except Exception as ex:
+                    print("[ELEMENTE] BoolDiff layer:", ex)
                 new_layer_breps.append((brep, color, lname))
             layer_breps = new_layer_breps