fixed costs tests

recommendations/Costs.py

@@ -308,12 +308,64 @@ class Costs:
 
         return {
             "total": total_cost,
-            "contengency": self.CONTINGENCIES["suspended_floor_insulation"] * total_cost,
+            "contingency": self.CONTINGENCIES["suspended_floor_insulation"] * total_cost,
             "contingency_rate": self.CONTINGENCIES["suspended_floor_insulation"],
             "labour_hours": labour_hours,
             "labour_days": labour_days,
         }
 
+    @staticmethod
+    def _estimate_number_of_days_for_solid_floor(insulation_floor_area: float) -> float:
+        """
+        Estimate the number of labour days required to install solid floor insulation,
+        based on the floor area being treated.
+
+        This is a heuristic (rule-of-thumb) estimate designed for early-stage planning
+        and costing. It deliberately avoids strict linear scaling because real-world
+        construction work includes fixed overheads and efficiency gains.
+
+        Core assumptions:
+        - A typical solid floor insulation job covering ~45 m2 takes around 7 working days.
+          This is based on market guidance (e.g. Checkatrade).
+        - Very small jobs still require multiple days due to setup, preparation,
+          curing/drying time, and inspections — even if the area is small.
+        - Larger jobs take longer, but each additional square metre adds slightly less
+          time than the previous one, because crews become more efficient once work
+          is underway.
+
+        The estimate therefore:
+        - Scales with floor area
+        - Applies a minimum realistic duration
+        - Uses non-linear scaling to reflect economies of scale
+
+        :param insulation_floor_area: float - total floor area to be insulated
+        """
+        # Reference case:
+        # A "typical" job (about half of a 90 m² house) takes ~7 days to complete
+        base_days = 7
+        base_area = 45  # m2 of solid floor insulated in the reference case
+
+        # Exponent < 1 means sub-linear scaling:
+        # doubling the area does NOT double the time, because setup costs
+        # and learning effects reduce the marginal effort per extra m²
+        labour_exponent = 0.85
+
+        # Minimum number of days for any solid floor job.
+        # Even small areas require mobilisation, preparation, installation,
+        # and finishing time, so jobs realistically won't complete faster than this.
+        min_days = 3
+
+        # Calculate estimated labour days:
+        # - Scale relative to the reference job
+        # - Apply sub-linear scaling for realism
+        # - Enforce a minimum duration so estimates are not unrealistically low
+        labour_days = max(
+            min_days,
+            base_days * (insulation_floor_area / base_area) ** labour_exponent
+        )
+
+        return labour_days
+
     def solid_floor_insulation(self, insulation_floor_area, material):
         """
         based on costing data from installers, produces an estimate for the cost of works. Returns contingency
@@ -324,21 +376,9 @@ class Costs:
         """
 
         total_cost = material["total_cost"] * insulation_floor_area
-
-        # We assume the average house takes ~7 days to complete at £300/day incl. VAT, as per checkatrade
-        # which can be seen here: https://www.checkatrade.com/blog/cost-guides/floor-insulation-cost
-        # Assumptions
-        base_days = 7  # The quickest it will be completed
-        base_area = 45  # The area that can be completed in that time (for a typical 90m2 house)
-        labour_exponent = 0.85  # Non-linear scaling
         daily_labour_rate = 300  # Based on checkatrade
 
-        min_days = 3  # Fewest days it will take
-        labour_days = max(
-            min_days,
-            base_days * (insulation_floor_area / base_area) ** labour_exponent
-        )
-
+        labour_days = self._estimate_number_of_days_for_solid_floor(insulation_floor_area)
         labour_cost = labour_days * daily_labour_rate
 
         total_cost = total_cost + labour_cost
@@ -460,7 +500,7 @@ class Costs:
         # We estimate the cost of an appliance thermostat at £400, which is the upper end of the range
         return {
             "total": total_cost,
-            "contengency": total_cost * self.CONTINGENCY,
+            "contingency": total_cost * self.CONTINGENCY,
             "contingency_rate": self.CONTINGENCY,
             "subtotal": subtotal_before_vat,
             "vat": vat,

recommendations/tests/test_costs.py

@@ -27,7 +27,8 @@ class TestCosts:
             material=cwi_material,
         )
 
-        assert cwi_results == {'total': 1342.7459938871539, 'labour_hours': 8, 'labour_days': 1}
+        assert cwi_results["total"] == 1342.7459938871539
+        assert cwi_results["contingency"] == 134.2745993887154
 
     def test_loft_insulation(self):
         mock_property = Mock()
@@ -37,6 +38,7 @@ class TestCosts:
 
         costs = Costs(mock_property)
         loft_material = {
+            "type": "loft_insulation",
             "description": "Crown Loft Roll 44 glass fibre roll",
             "depth": 270,
             "thermal_conductivity": 0.044,
@@ -50,7 +52,8 @@ class TestCosts:
             material=loft_material,
         )
 
-        assert loft_results == {'total': 368.5, 'labour_hours': 8, 'labour_days': 1}
+        assert loft_results["total"] == 368.5
+        assert loft_results["contingency"] == 36.85
 
     def test_internal_wall_insulation(self):
         mock_property = Mock()
@@ -79,9 +82,8 @@ class TestCosts:
             material=iwi_material,
         )
 
-        assert iwi_results == {
-            'total': 19182.085626959342, 'labour_hours': 17.263877064263404, 'labour_days': 0.5394961582582314
-        }
+        assert iwi_results["total"] == 19182.085626959342
+        assert iwi_results["contingency"] == 4987.342263009429
 
     def test_suspended_floor_insulation(self):
         mock_property = Mock()
@@ -98,53 +100,38 @@ class TestCosts:
             'thermal_conductivity_unit': 'watt_per_meter_kelvin', 'prime_material_cost': 0,
             'material_cost': 11.68, 'labour_cost': 1.78, 'labour_hours_per_unit': 0.1,
             'plant_cost': 0,
-            'total_cost': 13.46, 'link': 'SPONs',
-            'Notes': 'Spons did not contain labour costs so we use values for similar insulations. '
-                     'We use the '
-                     'same values as in Crown loft roll 44, since it is also an insulation roll',
+            'total_cost': 75,
             "is_installer_quote": False
         }
 
-        sus_floor_non_insulation_materials = [
-            {'type': 'suspended_floor_demolition', 'description': 'Removal of carpet and underfelt', 'depth': 0,
-             'depth_unit': 0, 'cost_unit': 0, 'thermal_conductivity': 0, 'thermal_conductivity_unit': 0,
-             'prime_material_cost': 0, 'material_cost': 0, 'labour_cost': 3.32, 'labour_hours_per_unit': 0.11,
-             'plant_cost': 0, 'total_cost': 3.32, 'link': 'SPONs',
-             'Notes': 'We ignore the plant cost that is in SPONs because we assume the carpet is not scrapped and '
-                      'therefore there is no need for a skip'},
-            {'type': 'suspended_floor_demolition',
-             'description': 'Remove boarding; withdraw nails; set aside for reuse; ground level', 'depth': 0,
-             'depth_unit': 0, 'cost_unit': 0, 'thermal_conductivity': 0, 'thermal_conductivity_unit': 0,
-             'prime_material_cost': 0, 'material_cost': 0, 'labour_cost': 9.34, 'labour_hours_per_unit': 0.3,
-             'plant_cost': 0, 'total_cost': 9.34, 'link': 'SPONs', 'Notes': 0},
-            {'type': 'suspended_floor_vapour_barrier', 'description': 'Visqueen High Performance Vapour Barrier',
-             'depth': 0, 'depth_unit': 0, 'cost_unit': 0, 'thermal_conductivity': 0,
-             'thermal_conductivity_unit': 0, 'prime_material_cost': 0.58, 'material_cost': 1.21, 'labour_cost': 0.48,
-             'labour_hours_per_unit': 0.02, 'plant_cost': 0, 'total_cost': 1.69, 'link': 'SPONs', 'Notes': 0},
-            {'type': 'suspended_floor_redecoration', 'description': 'refix floorboards previously set aside',
-             'depth': 0, 'depth_unit': 0, 'cost_unit': 0, 'thermal_conductivity': 0,
-             'thermal_conductivity_unit': 0, 'prime_material_cost': 0, 'material_cost': 1.54, 'labour_cost': 24.98,
-             'labour_hours_per_unit': 0.74, 'plant_cost': 0, 'total_cost': 26.52, 'link': 'SPONs', 'Notes': 0},
-            {'type': 'suspended_floor_redecoration', 'description': 'Fitting carpet', 'depth': 0, 'depth_unit': 0,
-             'cost_unit': 0, 'thermal_conductivity': 0, 'thermal_conductivity_unit': 0,
-             'prime_material_cost': 0, 'material_cost': 0, 'labour_cost': 6.59, 'labour_hours_per_unit': 0.37,
-             'plant_cost': 0, 'total_cost': 6.59, 'link': 'SPONs',
-             'Notes': 'SPONs does not have data on re-fitting the carpet so we use the data in Fitted carpeting; '
-                      'Gradus woven polypropylene tufted loop\n\n as a baseline. We assume re-use of carpets, '
-                      'therefore we need just labour rates'}]
-
         sus_floor_results = costs.suspended_floor_insulation(
             insulation_floor_area=33.5,
             material=sus_floor_material,
-            non_insulation_materials=sus_floor_non_insulation_materials
         )
 
-        assert sus_floor_results == {
-            'total': 3337.07436, 'subtotal': 2780.8953, 'vat': 556.17906, 'contingency': 370.78604,
-            'preliminaries': 185.39302, 'material': 483.405, 'profit': 370.78604, 'labour_hours': 54.940000000000005,
-            'labour_days': 2.289166666666667, 'labour_cost': 1370.5252
+        assert sus_floor_results["total"] == 2512.5
+        assert sus_floor_results["contingency"] == 502.5
+
+    @pytest.mark.parametrize("insulation_floor_area, expected_result", [
+        (5, 3),
+        (33.5, 5.446976345666071),
+        (45, 7),
+        (70, 10.190623048464415),
+        (90, 12.617506476551622),
+        (150, 19.47802744828744),
+        (200, 24.873843619763473),
+    ])
+    def test_estimate_estimate_number_of_days_for_solid_floor(
+        self, insulation_floor_area, expected_result
+    ):
+        mock_property = Mock()
+        mock_property.data = {
+            "county": "Northamptonshire"
         }
 
+        costs = Costs(mock_property)
+        assert costs._estimate_number_of_days_for_solid_floor(insulation_floor_area) == expected_result
+
     def test_solid_floor_insulation(self):
         mock_property = Mock()
         mock_property.data = {
@@ -160,75 +147,13 @@ class TestCosts:
             'total_cost': 16.42, 'link': 'SPONs', 'Notes': 0, "is_installer_quote": False
         }
 
-        sol_floor_non_insulation_materials = [
-            {'type': 'solid_floor_demolition', 'description': 'Removal of carpet and underfelt', 'depth': 0,
-             'depth_unit': 0, 'cost_unit': 0, 'thermal_conductivity': 0, 'thermal_conductivity_unit': 0,
-             'prime_material_cost': 0, 'material_cost': 0, 'labour_cost': 3.32, 'labour_hours_per_unit': 0.11,
-             'plant_cost': 0, 'total_cost': 3.32, 'link': 'SPONs',
-             'Notes': 'We ignore the plant cost that is in SPONs because we assume the carpet is not scrapped and '
-                      'therefore there is no need for a skip'},
-            {'type': 'solid_floor_preparation',
-             'description': 'clean surface of concrete to receive new damp-proof membrane', 'depth': 0,
-             'depth_unit': 0, 'cost_unit': 0, 'thermal_conductivity': 0, 'thermal_conductivity_unit': 0,
-             'prime_material_cost': 0, 'material_cost': 0, 'labour_cost': 4.36, 'labour_hours_per_unit': 0.14,
-             'plant_cost': 0, 'total_cost': 4.36, 'link': 0, 'Notes': 0}, {
-                'type': 'solid_floor_preparation',
-                'description': 'Clean out crack to '
-                               'form a 20mm×20mm '
-                               'groove and fill with '
-                               'cement: mortar mixed '
-                               'with bonding agent',
-                'depth': 0, 'depth_unit': 0,
-                'cost_unit': 0,
-                'thermal_conductivity': 0,
-                'thermal_conductivity_unit': 0,
-                'prime_material_cost': 0,
-                'material_cost': 6.91,
-                'labour_cost': 18.99,
-                'labour_hours_per_unit': 0.61,
-                'plant_cost': 0.16,
-                'total_cost': 26.06, 'link': 0,
-                'Notes': 'This step is the '
-                         'assessment and repair of '
-                         'any damage to the concrete '
-                         'floor such as filling '
-                         'cracks or levelling uneven '
-                         'areas'},
-            {'type': 'solid_floor_vapour_barrier', 'description': 'Visqueen High Performance Vapour Barrier',
-             'depth': 0, 'depth_unit': 0, 'cost_unit': 0, 'thermal_conductivity': 0,
-             'thermal_conductivity_unit': 0, 'prime_material_cost': 0.58, 'material_cost': 1.21, 'labour_cost': 0.48,
-             'labour_hours_per_unit': 0.02, 'plant_cost': 0, 'total_cost': 1.69, 'link': 'SPONs', 'Notes': 0},
-            {'type': 'solid_floor_redecoration',
-             'description': 'Screeded beds; protection to compressible formwork exceeding 600mm wide', 'depth': 0,
-             'depth_unit': 0, 'cost_unit': 0, 'thermal_conductivity': 0, 'thermal_conductivity_unit': 0,
-             'prime_material_cost': 9.6, 'material_cost': 9.89, 'labour_cost': 2.67, 'labour_hours_per_unit': 0.15,
-             'plant_cost': 0, 'total_cost': 12.56, 'link': 'SPONs',
-             'Notes': 'This is the screed layer, placed on top of the insulation'},
-            {'type': 'solid_floor_redecoration', 'description': 'Fitting carpet', 'depth': 0, 'depth_unit': 0,
-             'cost_unit': 0, 'thermal_conductivity': 0, 'thermal_conductivity_unit': 0,
-             'prime_material_cost': 0, 'material_cost': 0, 'labour_cost': 6.59, 'labour_hours_per_unit': 0.37,
-             'plant_cost': 0, 'total_cost': 6.59, 'link': 'SPONs',
-             'Notes': 'SPONs does not have data on re-fitting the carpet so we use the data in Fitted carpeting; '
-                      'Gradus woven polypropylene tufted loop\n\n as a baseline. We assume re-use of carpets, '
-                      'therefore we need just labour rates'},
-            {'type': 'solid_floor_redecoration',
-             'description': 'Fitting existing softwood skirting or architrave to new frames; 150mm high', 'depth': 0,
-             'depth_unit': 0, 'cost_unit': 0, 'thermal_conductivity': 0, 'thermal_conductivity_unit': 0,
-             'prime_material_cost': 0, 'material_cost': 0.01, 'labour_cost': 4.87, 'labour_hours_per_unit': 0.12,
-             'plant_cost': 0, 'total_cost': 4.88, 'link': 'SPONs', 'Notes': 0}
-        ]
-
         sol_floor_results = costs.solid_floor_insulation(
             insulation_floor_area=33.5,
             material=sol_floor_material,
-            non_insulation_materials=sol_floor_non_insulation_materials
         )
 
-        assert sol_floor_results == {
-            'total': 4245.023520000001, 'subtotal': 3537.5196, 'vat': 707.5039200000001, 'contingency': 471.66928,
-            'preliminaries': 235.83464, 'material': 1006.3399999999999, 'profit': 471.66928, 'labour_hours': 57.285,
-            'labour_days': 2.386875, 'labour_cost': 1346.6464
-        }
+        assert sol_floor_results["total"] == 2184
+        assert sol_floor_results["contingency"] == 567.84
 
     def test_external_wall_insulation(self):
         mock_property = Mock()
@@ -253,9 +178,8 @@ class TestCosts:
             material=ewi_material,
         )
 
-        assert ewi_results == {
-            'total': 28773.12844043901, 'labour_hours': 134.2745993887154, 'labour_days': 4.196081230897356
-        }
+        assert ewi_results["total"] == 28773.12844043901
+        assert ewi_results["contingency"] == 7481.013394514142
 
     def test_flat_roof_insulation(self):
         mock_property = Mock()
@@ -288,23 +212,27 @@ class TestCosts:
             material=flat_roof_material,
         )
 
-        assert flat_roof_floor_results == {
-            'total': 2063.935, 'subtotal': 1719.9458333333334, 'vat': 343.9891666666665, 'labour_hours': 8,
-            'labour_days': 1
-        }
+        assert flat_roof_floor_results["total"] == 2063.935
+        assert flat_roof_floor_results["contingency"] == 536.6231
 
         assert costs.labour_adjustment_factor == 0.88
 
     # Test for different wattages
-    @pytest.mark.parametrize("n_panels, expected_cost", [
-        (7, 5458.727999999999),
-        (10, 6013.139999999999),
-        (12, 6386.447999999999),
-        (15, 7594.451999999999),
+    @pytest.mark.parametrize("solar_product, expected_cost", [
+        ({"total_cost": 5000, "includes_scaffolding": False}, 6000),
+        ({"total_cost": 5000, "includes_scaffolding": True}, 5000),
     ])
-    def test_solar_pv_different_wattages(self, n_panels, expected_cost):
+    def test_solar_pv_different_wattages(self, solar_product, expected_cost):
         mock_property = Mock()
         mock_property.data = {"county": "Mansfield"}
+        scaffolding_options = [
+            {"size": 2, "total_cost": 1000}
+        ]
         costs = Costs(mock_property)
-        result = costs.solar_pv(n_panels)
+        result = costs.solar_pv(
+            solar_product=solar_product,
+            scaffolding_options=scaffolding_options,
+            n_floors=2
+        )
+
         assert result['total'] == pytest.approx(expected_cost, rel=0.01)