diff --git a/datatypes/epc/domain/mapper.py b/datatypes/epc/domain/mapper.py
index 10ec411d..26704922 100644
--- a/datatypes/epc/domain/mapper.py
+++ b/datatypes/epc/domain/mapper.py
@@ -2172,7 +2172,7 @@ class EpcPropertyDataMapper:
             # to 0 like every other mapper (RdSAP "not lodged" → calc minimum 1).
             wet_rooms_count=schema.wet_rooms_count or 0,
             extensions_count=schema.extensions_count,
-            open_chimneys_count=schema.open_chimneys_count,
+            open_chimneys_count=schema.open_chimneys_count or 0,
             insulated_door_count=schema.insulated_door_count,
             draughtproofed_door_count=schema.draughtproofed_door_count,
             # Mechanical ventilation PCDB plumbing — feeds the §5 Table 4f
@@ -2188,8 +2188,8 @@ class EpcPropertyDataMapper:
             ),
             mechanical_vent_duct_type=schema.mechanical_vent_duct_type,
             # Lighting
-            led_fixed_lighting_bulbs_count=schema.led_fixed_lighting_bulbs_count,
-            cfl_fixed_lighting_bulbs_count=schema.cfl_fixed_lighting_bulbs_count,
+            led_fixed_lighting_bulbs_count=schema.led_fixed_lighting_bulbs_count or 0,
+            cfl_fixed_lighting_bulbs_count=schema.cfl_fixed_lighting_bulbs_count or 0,
             incandescent_fixed_lighting_bulbs_count=schema.incandescent_fixed_lighting_bulbs_count,
             # Energy elements
             roofs=EpcPropertyDataMapper._map_energy_elements(schema.roofs),
diff --git a/datatypes/epc/domain/tests/test_from_rdsap_schema.py b/datatypes/epc/domain/tests/test_from_rdsap_schema.py
index a2463eae..440325ce 100644
--- a/datatypes/epc/domain/tests/test_from_rdsap_schema.py
+++ b/datatypes/epc/domain/tests/test_from_rdsap_schema.py
@@ -431,6 +431,33 @@ class TestFromRdSapSchema21_0_1:
 
         assert result.wet_rooms_count == 0
 
+    def test_omitted_open_chimneys_count_defaults_to_zero_not_none(self) -> None:
+        data = load("21_0_1.json")
+        data.pop("open_chimneys_count", None)
+        schema = from_dict(RdSapSchema21_0_1, data)
+
+        result = EpcPropertyDataMapper.from_rdsap_schema_21_0_1(schema)
+
+        assert result.open_chimneys_count == 0
+
+    def test_omitted_cfl_fixed_lighting_bulbs_count_defaults_to_zero_not_none(self) -> None:
+        data = load("21_0_1.json")
+        data.pop("cfl_fixed_lighting_bulbs_count", None)
+        schema = from_dict(RdSapSchema21_0_1, data)
+
+        result = EpcPropertyDataMapper.from_rdsap_schema_21_0_1(schema)
+
+        assert result.cfl_fixed_lighting_bulbs_count == 0
+
+    def test_omitted_led_fixed_lighting_bulbs_count_defaults_to_zero_not_none(self) -> None:
+        data = load("21_0_1.json")
+        data.pop("led_fixed_lighting_bulbs_count", None)
+        schema = from_dict(RdSapSchema21_0_1, data)
+
+        result = EpcPropertyDataMapper.from_rdsap_schema_21_0_1(schema)
+
+        assert result.led_fixed_lighting_bulbs_count == 0
+
     def test_uprn(self, result: EpcPropertyData) -> None:
         assert result.uprn == 12457
 
diff --git a/tests/harness/test_report.py b/tests/harness/test_report.py
index 6b8bc9a4..304f8940 100644
--- a/tests/harness/test_report.py
+++ b/tests/harness/test_report.py
@@ -179,7 +179,7 @@ def test_few_measure_cert_surfaces_only_its_fired_measures_triggers() -> None:
     }
     assert triggers["low_energy_lighting"].triggers == {
         "incandescent_fixed_lighting_bulbs_count": 0,
-        "cfl_fixed_lighting_bulbs_count": None,
+        "cfl_fixed_lighting_bulbs_count": 0,
         "low_energy_fixed_lighting_bulbs_count": 7,
     }