Model/recommendations/Costs.py

import numpy as np
from recommendations.county_to_region import county_to_region_map

# This data comes from SPONs 2023
regional_labour_variations = [
    {"Region": "Outer London", "Adjustment_Factor": 1.00},
    {"Region": "Inner London", "Adjustment_Factor": 1.05},
    {"Region": "South East England", "Adjustment_Factor": 0.96},
    {"Region": "South West England", "Adjustment_Factor": 0.90},
    {"Region": "East of England", "Adjustment_Factor": 0.93},
    {"Region": "East Midlands", "Adjustment_Factor": 0.88},
    {"Region": "West Midlands", "Adjustment_Factor": 0.87},
    {"Region": "North East England", "Adjustment_Factor": 0.83},
    {"Region": "North West England", "Adjustment_Factor": 0.88},
    {"Region": "Yorkshire and the Humber", "Adjustment_Factor": 0.86},
    {"Region": "Wales", "Adjustment_Factor": 0.88},
    {"Region": "Scotland", "Adjustment_Factor": 0.88},
    {"Region": "Northern Ireland", "Adjustment_Factor": 0.76}
]


class Costs:
    """
    A class to calculate the costs associated with construction works,
    specifically focusing on cavity wall insulation.
    It includes contingency, preliminaries, profit margin, and VAT calculations.

    As a sense check, there is a useful article from checkatrade on retrofitting and expected costs:
    https://www.checkatrade.com/blog/cost-guides/retrofit-insulation-cost/

    Another useful article for benchmarking the cost of floor insulation:
    https://www.checkatrade.com/blog/cost-guides/floor-insulation-cost/
    """

    # Contingency is a percentage of the total cost of the work and covers unforseen expenses
    # We assume a conservative 10% contingency for all works which is a rate defined by SPONs
    CONTINGENCY = 0.1

    # For flat roof, we assume it's a high risk project as it's very weather dependent and also is heavily
    # dependent on the quality of the existing roof
    FLAT_ROOF_CONTINGENCY = 0.15

    # We use a higher contingency rate for internal wall insulation because of the potential for issues with moving
    # fittings and trimming doors, as well as scope for damage to the existing wall during preparation.
    IWI_CONTINGENCY = 0.15

    # Where there is more uncertainty, a higher contingency rate is used
    HIGH_RISK_CONTINGENCY = 0.2
    # When there is less uncertainty, a lower contingency rate is used
    LOW_RISK_CONTINGENCY = 0.05

    # Preliminaries are a percentage of the total cost of the work and covers the cost of site-specific costs
    # such as site preparation, safety measures and project management. This rate can vary but we'll assume a 10%
    # rate, on the total cost before VAT, as recommended by SPONs
    PRELIMINARIES = 0.1

    # For higher risk projects, a higher preliminaries rate is used. SPONs indicates that a higher risk project might
    # have a preliminaries of 12-14% so we use 12% as the median for the preliminaries rate.
    # For External wall insulation (EWI), we use 15% as the preliminaries rate if we think the property might
    # need scaffolding, otherwise we use 12%. This is to account for any site preparation that might be required
    EWI_NO_SCAFFOLDING_PRELIMINARIES = 0.15
    EWI_SCAFFOLDING_PRELIMINARIES = 0.20

    VAT_RATE = 0.2
    PROFIT_MARGIN = 0.2

    def __init__(self, property_instance):
        """
        Initializes the Costs class with a property instance.

        :param property_instance: Instance of a Property class containing relevant details like wall area.
        """
        if not hasattr(property_instance, 'insulation_wall_area'):
            raise ValueError("Property instance must have an 'insulation_wall_area' attribute")
        self.property = property_instance
        self.regional_labour_variations = regional_labour_variations

        self.region = county_to_region_map.get(self.property.data["county"], None)
        if self.region is None:
            # Try and grab using the local-authority-label
            self.region = county_to_region_map.get(self.property.data["local-authority-label"], None)
            if self.region is None:
                raise ValueError("Region not found in county map")

        self.labour_adjustment_factor = [
            x["Adjustment_Factor"] for x in self.regional_labour_variations if
            x["Region"] == self.region
        ][0]

        if not self.labour_adjustment_factor:
            raise ValueError("Labour adjustment factor not found")

    def cavity_wall_insulation(self, wall_area, material):
        """
        Calculates the total cost for cavity wall insulation based on material and labor costs,
        including contingency, preliminaries, profit, and VAT.

        Because of some limitations in the SPONs data, there are no materials that can be blown through a wall,
        therefore we have adapted similar materials, basing our estimates on 75mm cavity slabs, and have halved the
        labour time required. That is why we still price based on wall area despite volume actually being the correct
        metric.

        :return: A dictionary containing detailed cost breakdown.
        """

        material_cost_per_m2 = material["material_cost"]

        base_material_cost = material_cost_per_m2 * wall_area
        labour_cost = material["labour_cost"] * wall_area * self.labour_adjustment_factor

        subtotal_before_profit = base_material_cost + labour_cost

        contingency_cost = subtotal_before_profit * self.CONTINGENCY
        preliminaries_cost = subtotal_before_profit * self.PRELIMINARIES
        profit_cost = subtotal_before_profit * self.PROFIT_MARGIN

        subtotal_before_vat = subtotal_before_profit + contingency_cost + preliminaries_cost + profit_cost

        vat_cost = subtotal_before_vat * self.VAT_RATE

        total_cost = subtotal_before_vat + vat_cost

        labour_hours = material["labour_hours_per_unit"] * wall_area

        # Assume a team of 2
        labour_days = (labour_hours / 8) / 2

        return {
            "total": total_cost,
            "subtotal": subtotal_before_vat,
            "vat": vat_cost,
            "contingency": contingency_cost,
            "preliminaries": preliminaries_cost,
            "material": base_material_cost,
            "profit": profit_cost,
            "labour_hours": labour_hours,
            "labour_cost": labour_cost,
            "labour_days": labour_days
        }

    def loft_insulation(self, floor_area, material):
        """
        Calculates the total cost for cavity wall insulation based on material and labor costs,
        including contingency, preliminaries, profit, and VAT.

        :return: A dictionary containing detailed cost breakdown.
        """
        material_cost_per_m2 = material["material_cost"]

        base_material_cost = material_cost_per_m2 * floor_area
        labour_cost = material["labour_cost"] * floor_area * self.labour_adjustment_factor

        subtotal_before_profit = base_material_cost + labour_cost

        contingency_cost = subtotal_before_profit * self.CONTINGENCY
        preliminaries_cost = subtotal_before_profit * self.PRELIMINARIES
        profit_cost = subtotal_before_profit * self.PROFIT_MARGIN

        subtotal_before_vat = subtotal_before_profit + contingency_cost + preliminaries_cost + profit_cost

        vat_cost = subtotal_before_vat * self.VAT_RATE

        total_cost = subtotal_before_vat + vat_cost

        labour_hours = material["labour_hours_per_unit"] * floor_area

        # Assume a team of 1 person
        labour_days = labour_hours / 8

        return {
            "total": total_cost,
            "subtotal": subtotal_before_vat,
            "vat": vat_cost,
            "contingency": contingency_cost,
            "preliminaries": preliminaries_cost,
            "material": base_material_cost,
            "profit": profit_cost,
            "labour_hours": labour_hours,
            "labour_cost": labour_cost,
            "labour_days": labour_days
        }

    def internal_wall_insulation(self, wall_area, material, non_insulation_materials):
        """
        Broadly speaking, the high level steps to an internal wall insulation job are the following:

        1) Demolition: This involves removing existing wall linings, fittings, and any other obstacles.
        It's important to factor in the disposal of debris and the potential need for additional protective
        measures to ensure the safety of the work area.

        2) Insulation Installation: This is the core part of the process where the chosen insulation material is
        applied. The choice of insulation material will depend on several factors including thermal performance,
        wall construction, and space constraints.

        3) Vapour Barrier Installation: This is crucial for preventing moisture from penetrating the insulation,
        which can compromise its effectiveness and lead to mold growth.

        4) Re-decoration: This involves applying plaster to the wall and then painting.
        The quality of finish here is important for both aesthetic and functional reasons.

        5) Trim and Finishing Work: Post-insulation, tasks such as re-installing skirting boards, door frames,
        or window sills might be necessary.
        :return:
        """

        # Extract and check the different types of data we'll need
        demolition_data = [x for x in non_insulation_materials if x["type"] == "iwi_wall_demolition"]
        vapour_barrier_data = [x for x in non_insulation_materials if x["type"] == "iwi_vapour_barrier"]
        redecoration_data = [x for x in non_insulation_materials if x["type"] == "iwi_redecoration"]
        if not demolition_data:
            raise ValueError("No data found for iwi_wall_demolition")

        if (len(vapour_barrier_data) != 1) or (len(redecoration_data) != 3):
            raise ValueError("Incorrect number of data entries for non-insulation materials")

        # Break out the individual material costs
        # Since we don't know the exact wall construction, we take an average for demolition costs, since
        # the cost will depend on the type of wall construction
        demolition_material_costs = np.mean([x["material_cost"] * wall_area for x in demolition_data])
        insulation_material_costs = material["material_cost"] * wall_area
        vapour_barrier_material_costs = vapour_barrier_data[0]["material_cost"] * wall_area
        redecoration_material_costs = sum([x["material_cost"] * wall_area for x in redecoration_data])

        demolition_plant_costs = np.mean([x["plant_cost"] * wall_area for x in demolition_data])

        # Again for demolition, we average since we aren't sure which demolition process will be used
        demolition_labour_costs = np.mean([x["labour_cost"] * wall_area for x in demolition_data])
        insulation_labour_costs = material["labour_cost"] * wall_area
        vapour_barrier_labour_costs = vapour_barrier_data[0]["labour_cost"] * wall_area
        redecoration_labour_costs = sum([x["labour_cost"] * wall_area for x in redecoration_data])

        labour_costs = (demolition_labour_costs + insulation_labour_costs + vapour_barrier_labour_costs +
                        redecoration_labour_costs)

        labour_costs = labour_costs * self.labour_adjustment_factor

        materials_costs = (demolition_material_costs + insulation_material_costs + vapour_barrier_material_costs +
                           redecoration_material_costs)

        subtotal_before_profit = labour_costs + materials_costs + demolition_plant_costs

        contingency_cost = subtotal_before_profit * self.IWI_CONTINGENCY
        preliminaries_cost = subtotal_before_profit * self.PRELIMINARIES
        profit_cost = subtotal_before_profit * self.PROFIT_MARGIN

        subtotal_before_vat = subtotal_before_profit + contingency_cost + preliminaries_cost + profit_cost

        vat_cost = subtotal_before_vat * self.VAT_RATE

        total_cost = subtotal_before_vat + vat_cost

        demolition_labour_hours = np.mean([x["labour_hours_per_unit"] * wall_area for x in demolition_data])
        insulation_labour_hours = material["labour_hours_per_unit"] * wall_area
        vapour_barrier_labour_hours = vapour_barrier_data[0]["labour_hours_per_unit"] * wall_area
        redecoration_labour_hours = sum([x["labour_hours_per_unit"] * wall_area for x in redecoration_data])

        labour_hours = (demolition_labour_hours + insulation_labour_hours + vapour_barrier_labour_hours +
                        redecoration_labour_hours)

        # To install internal wall insulation, a small to medium size project might be conducted by a team of 3-5 people
        labour_days = (labour_hours / 8) / 4

        return {
            "total": total_cost,
            "subtotal": subtotal_before_vat,
            "vat": vat_cost,
            "contingency": contingency_cost,
            "preliminaries": preliminaries_cost,
            "material": materials_costs,
            "profit": profit_cost,
            "labour_hours": labour_hours,
            "labour_days": labour_days,
            "labour_cost": labour_costs
        }

    def suspended_floor_insulation(self, insulation_floor_area, material, non_insulation_materials):
        """
        We characterise the steps for suspended floor insulation as the following tasks:

        1) Removal of Carpet and Underfelt: Where necessary, remove existing floor coverings to access the floorboards.
        2) Removal of Floor Boarding: Carefully remove floorboards to access the space beneath for insulation.
        3) Installation of Vapour Barrier: Install a vapour barrier to prevent moisture from affecting
        the insulation and floor structure.
        4) Installation of Insulation: Fit the chosen insulation material between the joists in the floor void.
        5) Refixing Floorboards: Replace and secure the floorboards after insulation installation.
        6) Re-carpeting: Lay down the carpet or other floor coverings once the insulation and floorboards are in place.
        :return:
        """

        demolition_data = [x for x in non_insulation_materials if x["type"] == "suspended_floor_demolition"]
        vapour_barrier_data = [x for x in non_insulation_materials if x["type"] == "suspended_floor_vapour_barrier"]
        redecoration_data = [x for x in non_insulation_materials if x["type"] == "suspended_floor_redecoration"]

        if (len(demolition_data) != 2) or (len(vapour_barrier_data) != 1) or (len(redecoration_data) != 2):
            raise ValueError("Incorrect number of data entries for non-insulation materials")

        # Break out the individual material costs
        demolition_material_costs = sum([x["material_cost"] * insulation_floor_area for x in demolition_data])
        insulation_material_costs = material["material_cost"] * insulation_floor_area
        vapour_barrier_material_costs = vapour_barrier_data[0]["material_cost"] * insulation_floor_area
        redecoration_material_costs = sum([x["material_cost"] * insulation_floor_area for x in redecoration_data])

        demolition_labour_costs = sum([x["labour_cost"] * insulation_floor_area for x in demolition_data])
        insulation_labour_costs = material["labour_cost"] * insulation_floor_area
        vapour_barrier_labour_costs = vapour_barrier_data[0]["labour_cost"] * insulation_floor_area
        redecoration_labour_costs = sum([x["labour_cost"] * insulation_floor_area for x in redecoration_data])

        labour_costs = (demolition_labour_costs + insulation_labour_costs + vapour_barrier_labour_costs +
                        redecoration_labour_costs)

        labour_costs = labour_costs * self.labour_adjustment_factor

        materials_costs = (demolition_material_costs + insulation_material_costs + vapour_barrier_material_costs +
                           redecoration_material_costs)

        subtotal_before_profit = labour_costs + materials_costs

        contingency_cost = subtotal_before_profit * self.CONTINGENCY
        preliminaries_cost = subtotal_before_profit * self.PRELIMINARIES
        profit_cost = subtotal_before_profit * self.PROFIT_MARGIN

        subtotal_before_vat = subtotal_before_profit + contingency_cost + preliminaries_cost + profit_cost

        vat_cost = subtotal_before_vat * self.VAT_RATE

        total_cost = subtotal_before_vat + vat_cost

        demolition_labour_hours = sum([x["labour_hours_per_unit"] * insulation_floor_area for x in demolition_data])
        insulation_labour_hours = material["labour_hours_per_unit"] * insulation_floor_area
        vapour_barrier_labour_hours = vapour_barrier_data[0]["labour_hours_per_unit"] * insulation_floor_area
        redecoration_labour_hours = sum([x["labour_hours_per_unit"] * insulation_floor_area for x in redecoration_data])

        labour_hours = (demolition_labour_hours + insulation_labour_hours + vapour_barrier_labour_hours +
                        redecoration_labour_hours)

        # Assume a team of 3 people for a small to medium size project
        labour_days = (labour_hours / 8) / 3

        return {
            "total": total_cost,
            "subtotal": subtotal_before_vat,
            "vat": vat_cost,
            "contingency": contingency_cost,
            "preliminaries": preliminaries_cost,
            "material": materials_costs,
            "profit": profit_cost,
            "labour_hours": labour_hours,
            "labour_days": labour_days,
            "labour_cost": labour_costs
        }

    def solid_floor_insulation(self, insulation_floor_area, material, non_insulation_materials):
        """
        We characterise the steps for solid floor insulation as the following tasks:

        1) Removal of Carpet and Underfelt: This is the initial stage where any existing floor coverings, like carpets,
        tiles, or linoleum, are carefully removed. This exposes the solid floor beneath, which is typically concrete.

        2) Preparation of Flooring: This step is critical. It involves:
        - Cleaning the existing floor surface thoroughly to remove debris and ensure a flat surface.
        - Assessing and repairing any damage to the concrete floor. This might include filling cracks or leveling
        uneven areas.

        3) Installation of a Damp Proof Membrane (DPM): Before installing insulation, a DPM is often laid down to
        prevent moisture from rising into the insulation and the interior space. This step is crucial in areas prone to
        dampness.

        4) Install Insulation: The insulation, often in the form of rigid foam boards, is laid over the DPM.
        The choice of insulation material will depend on the desired thermal properties and the available floor height.
        Care is taken to minimize thermal bridges and ensure a snug fit between insulation boards.

        5) Laying a New Subfloor: Over the insulation, a new subfloor is often installed. This could be a layer of
        screed (a type of concrete) or wooden boarding, depending on the specific requirements and preferences.

        6) Re-decoration and Finishing Touches: Once the subfloor is in place and has set or dried (if necessary),
        the final floor finish can be applied. This might involve:
        - Laying new tiles, wooden flooring, or other chosen materials.
        - If you're planning to re-carpet, this would be the stage to do it.
        - Skirting boards may need to be refitted or replaced.

        7) Considerations for Doors and Fixtures: It's important to note that raising the floor level can affect door
        thresholds and other fixtures. Doors may need to be trimmed, and fixtures might need adjustments.

        :param insulation_floor_area: Area of the floor to be insulated
        :param material: Selected insulation material
        :param non_insulation_materials: Non-insulation materials required for the job
        :return:
        """

        demolition_data = [x for x in non_insulation_materials if x["type"] == "solid_floor_demolition"]
        preparation_data = [x for x in non_insulation_materials if x["type"] == "solid_floor_preparation"]
        vapour_barrier_data = [x for x in non_insulation_materials if x["type"] == "solid_floor_vapour_barrier"]
        redecoration_data = [x for x in non_insulation_materials if x["type"] == "solid_floor_redecoration"]

        if ((len(demolition_data) != 1) or (len(preparation_data) != 2) or (len(vapour_barrier_data) != 1) or
            (len(redecoration_data) != 3)):
            raise ValueError("Incorrect number of data entries for non-insulation materials")

        # Break out the individual material costs
        preparation_material_costs = sum([x["material_cost"] * insulation_floor_area for x in preparation_data])
        insulation_material_costs = material["material_cost"] * insulation_floor_area
        vapour_barrier_material_costs = vapour_barrier_data[0]["material_cost"] * insulation_floor_area
        redecoration_material_costs = sum([x["material_cost"] * insulation_floor_area for x in redecoration_data])

        demolition_labour_costs = sum([x["labour_cost"] * insulation_floor_area for x in demolition_data])
        preparation_labour_costs = sum([x["labour_cost"] * insulation_floor_area for x in preparation_data])
        insulation_labour_costs = material["labour_cost"] * insulation_floor_area
        vapour_barrier_labour_costs = vapour_barrier_data[0]["labour_cost"] * insulation_floor_area
        redecoration_labour_costs = sum([x["labour_cost"] * insulation_floor_area for x in redecoration_data])

        preparation_plant_costs = sum([x["plant_cost"] * insulation_floor_area for x in preparation_data])

        labour_costs = (demolition_labour_costs + insulation_labour_costs + vapour_barrier_labour_costs +
                        redecoration_labour_costs + preparation_labour_costs)

        labour_costs = labour_costs * self.labour_adjustment_factor

        materials_cost = (preparation_material_costs + insulation_material_costs + vapour_barrier_material_costs +
                          redecoration_material_costs)

        subtotal_before_profit = labour_costs + materials_cost + preparation_plant_costs

        # We use HIGH_RISH_CONTINGENCY because of the potential for issues with moving fittings and trimming doors,
        # as well as scope for damage to the existing floor during preparation.
        contingency_cost = subtotal_before_profit * self.HIGH_RISK_CONTINGENCY
        preliminaries_cost = subtotal_before_profit * self.PRELIMINARIES
        profit_cost = subtotal_before_profit * self.PROFIT_MARGIN

        subtotal_before_vat = subtotal_before_profit + contingency_cost + preliminaries_cost + profit_cost
        vat_cost = subtotal_before_vat * self.VAT_RATE
        total_cost = subtotal_before_vat + vat_cost

        demolition_labour_hours = sum([x["labour_hours_per_unit"] * insulation_floor_area for x in demolition_data])
        preparation_labour_hours = sum([x["labour_hours_per_unit"] * insulation_floor_area for x in preparation_data])
        insulation_labour_hours = material["labour_hours_per_unit"] * insulation_floor_area
        vapour_barrier_labour_hours = vapour_barrier_data[0]["labour_hours_per_unit"] * insulation_floor_area
        redecoration_labour_hours = sum([x["labour_hours_per_unit"] * insulation_floor_area for x in redecoration_data])

        labour_hours = (demolition_labour_hours + insulation_labour_hours + vapour_barrier_labour_hours +
                        redecoration_labour_hours + preparation_labour_hours)

        # Assume a team of 3 people for a small to medium size project
        labour_days = (labour_hours / 8) / 3

        return {
            "total": total_cost,
            "subtotal": subtotal_before_vat,
            "vat": vat_cost,
            "contingency": contingency_cost,
            "preliminaries": preliminaries_cost,
            "material": materials_cost,
            "profit": profit_cost,
            "labour_hours": labour_hours,
            "labour_days": labour_days,
            "labour_cost": labour_costs
        }

    def external_wall_insulation(self, wall_area, material, non_insulation_materials):
        """
        We characterise external wall insulation as the following steps:

        1) Preparation of the Area: Tidying up the surroundings, trimming back foliage, and laying down protective
        sheets to protect the flooring and landscaping around the work area.

        2) Scaffolding Setup (if needed): Erecting scaffolding for safe access to the walls of semi-detached or
        detached houses. For terraced houses or lower-level work, scaffolding might not be necessary.

        3) Wall Surface Preparation: Cleaning the wall surface, removing any loose or flaking material,
        and possibly applying a primer. If the existing wall is weak or damaged, partial or full replacement
        of the top surface may be necessary.

        4) Applying Primer: If the existing wall is suitable, applying a primer to improve adhesion of the insulation
        boards and stabilize the wall surface, especially if it's old or weathered.

        5) Insulation Application: Attaching insulation boards to the primed wall using adhesive, mechanical fixings,
        or a combination of both.

        6) Basecoat and Mesh Application: Applying a basecoat embedded with a reinforcing mesh over the insulation.
        This layer provides strength and helps prevent cracking.

        7) Decorative Finish: Applying a decorative finish, such as render or cladding, which protects the insulation
        and provides an aesthetic look.

        8) Reinstalling Fixtures: Reattaching any fixtures like downpipes, satellite dishes, or lighting fixtures that
        were removed during preparation. Extensions or adjustments may be required due to the increased wall thickness.

        9) Inspection and Cleanup: Conducting a thorough inspection to ensure quality and integrity of the EWI system,
        followed by cleaning up the site to remove all debris and materials.

        In the actual materials data, at this point, we have costing for:
        - wall preparation, hacking off existing wall finishes, linings, etc (ewi_wall_demolition)
        - wall surface cleaning and priming (ewi_wall_preparation)
        - insulation (external_wall_insulation)
        - basecoat and mesh with decorative render topcoat finish (ewi_basecoat_and_mesh)

        All of this data comes from SPONS, however there are some clear features missing. Because we could not find
        suitable cost records in SPONS for steps like cleaning the area, setting up small scale scaffolding,
        re-attaching any fitings and cleaning up the area afterwards, instead we have accounted for these steps by
        increasing the preliminaries rate. It is acknowldeged though, that this is not ideal and that the cost of these
        steps should be included in the materials data. We will look to improve this in the future, with data from
        installers

        :param wall_area:
        :param material:
        :param non_insulation_materials:
        :return:
        """

        # For semi detatched and detatched houses, as well as maisonettes, we price for scaffolding

        if self.property.data["property-type"] == "House":
            if self.property.data["built-form"] in ['Semi-Detached', 'Detached', "End-Terrace"]:
                preliminaries_rate = self.EWI_SCAFFOLDING_PRELIMINARIES
            else:
                preliminaries_rate = self.EWI_NO_SCAFFOLDING_PRELIMINARIES
        elif self.property.data["property-type"] == "Maisonette":
            preliminaries_rate = self.EWI_SCAFFOLDING_PRELIMINARIES
        elif self.property.data["property-type"] == "Bungalow":
            preliminaries_rate = self.EWI_NO_SCAFFOLDING_PRELIMINARIES
        else:
            raise ValueError("Unsupported property type - haven't handled flats")

        demolition_data = [x for x in non_insulation_materials if x["type"] == "ewi_wall_demolition"]
        preparation_data = [x for x in non_insulation_materials if x["type"] == "ewi_wall_preparation"]
        redecoration_data = [x for x in non_insulation_materials if x["type"] == "ewi_wall_redecoration"]

        if (len(demolition_data) != 3) or (len(preparation_data) != 1) or (len(redecoration_data) != 1):
            raise ValueError("Incorrect number of data entries for non-insulation materials")

        # Break out the individual material costs
        # Since we don't know the exact wall construction, we take an average for demolition costs, since
        # the cost will depend on the type of wall construction
        demolition_material_costs = np.mean([x["material_cost"] * wall_area for x in demolition_data])
        insulation_material_costs = material["material_cost"] * wall_area
        preparation_material_costs = preparation_data[0]["material_cost"] * wall_area
        redecoration_material_costs = redecoration_data[0]["material_cost"] * wall_area

        demolition_plant_costs = np.mean([x["plant_cost"] * wall_area for x in demolition_data])

        demolition_labour_costs = np.mean([x["labour_cost"] * wall_area for x in demolition_data])
        insulation_labour_costs = material["labour_cost"] * wall_area
        preparation_labour_costs = preparation_data[0]["labour_cost"] * wall_area
        redecoration_labour_costs = redecoration_data[0]["labour_cost"] * wall_area

        labour_costs = (demolition_labour_costs + insulation_labour_costs + redecoration_labour_costs +
                        preparation_labour_costs)

        labour_costs = labour_costs * self.labour_adjustment_factor

        materials_costs = (demolition_material_costs + insulation_material_costs + preparation_material_costs +
                           redecoration_material_costs)

        subtotal_before_profit = labour_costs + materials_costs + demolition_plant_costs

        contingency_cost = subtotal_before_profit * self.CONTINGENCY
        preliminaries_cost = subtotal_before_profit * preliminaries_rate
        profit_cost = subtotal_before_profit * self.PROFIT_MARGIN

        subtotal_before_vat = subtotal_before_profit + contingency_cost + preliminaries_cost + profit_cost
        vat_cost = subtotal_before_vat * self.VAT_RATE
        total_cost = subtotal_before_vat + vat_cost

        demolition_labour_hours = np.mean([x["labour_hours_per_unit"] * wall_area for x in demolition_data])
        insulation_labour_hours = material["labour_hours_per_unit"] * wall_area
        preparation_labour_hours = preparation_data[0]["labour_hours_per_unit"] * wall_area
        redecoration_labour_hours = redecoration_data[0]["labour_hours_per_unit"] * wall_area

        labour_hours = (demolition_labour_hours + insulation_labour_hours + redecoration_labour_hours +
                        preparation_labour_hours)

        # Assume a team of 3-5 people for a small to medium size project
        labour_days = (labour_hours / 8) / 4

        return {
            "total": total_cost,
            "subtotal": subtotal_before_vat,
            "vat": vat_cost,
            "contingency": contingency_cost,
            "preliminaries": preliminaries_cost,
            "material": materials_costs,
            "profit": profit_cost,
            "labour_hours": labour_hours,
            "labour_days": labour_days,
            "labour_cost": labour_costs
        }

    def low_energy_lighting(self, number_of_lights, number_current_lel_lights, material):

        """
        Calculates the total cost for low energy lighting based on material and labor costs,
        including contingency, preliminaries, profit, and VAT.

        :param number_of_lights: Int, number of light
        :param number_current_lel_lights:  Int, number of low energy lights currently installed in the home
        :material: Dict, material data containing costs of fittings
        """

        # If there are no lights fitted in the property, we increase the contingency in case there are potential wiring
        # blockers
        if number_current_lel_lights == 0:
            contingency = self.HIGH_RISK_CONTINGENCY
        else:
            contingency = self.CONTINGENCY

        material_cost = material["material_cost"] * number_of_lights
        labour_cost = material["labour_cost"] * number_of_lights * self.labour_adjustment_factor

        subtotal_before_profit = material_cost + labour_cost

        contingency_cost = subtotal_before_profit * contingency
        preliminaries_cost = subtotal_before_profit * self.PRELIMINARIES
        profit_cost = subtotal_before_profit * self.PROFIT_MARGIN

        subtotal_before_vat = subtotal_before_profit + contingency_cost + preliminaries_cost + profit_cost
        vat_cost = subtotal_before_vat * self.VAT_RATE
        total_cost = subtotal_before_vat + vat_cost

        labour_hours = material["labour_hours_per_unit"] * number_of_lights
        # Assume a single electrician installing
        labour_days = (labour_hours / 8)

        return {
            "total": total_cost,
            "subtotal": subtotal_before_vat,
            "vat": vat_cost,
            "contingency": contingency_cost,
            "preliminaries": preliminaries_cost,
            "material": material_cost,
            "profit": profit_cost,
            "labour_hours": labour_hours,
            "labour_days": labour_days,
            "labour_cost": labour_cost
        }

    def flat_roof_insulation(self, floor_area, material, non_insulation_materials):
        """
        A model of a warm, flat roof construction can be seen in this video:
        https://www.youtube.com/watch?v=WZ6Ng6YI9OA
        Warm, flat roof insulation will normally be 100-125mm in depth

        We break this measure down into the following jobs to be done
        1) Preparation of the room. This involves cleaning the existing roof surface, removing any debris and repairing
        any damage. Additionally, an edge barrier will likely need to be installed, to protect the sides of the
        roof from water ingress.
        2) Primer Application. A layer of primer is applied to the clean roof surface to enhance the adhestia of
        subsequent layers, and seal the existing roof surface.
        3) Vapour Proof Layer Installation. Lay a vapour control layer to prevent moisture ingress from inside the
        building, which is essential in warm roof construction.
        4) Insulation Layer Application. Place and securely fix insulation boards over the roof. These could be rigid
        boards like PIR (Polyisocyanurate).
        5) Waterproofing Membrane Installation: Cover the insulation (and timber layer, if used) with a
        waterproofing membrane, like EPDM, PVC, or bituminous felt.  Carefully seal all joints, edges, and around any
        roof penetrations to ensure water tightness

        :param floor_area: Area of the flat roof to be insulated, based on the area of the floor
        :param material: Selected insulation material
        :param non_insulation_materials: Non-insulation materials required for the job
        :return:
        """

        preparation_data_m2 = [
            x for x in non_insulation_materials if
            (x["type"] == "flat_roof_preparation") and (x["cost_unit"] == "gbp_per_m2")
        ]
        vapour_barrier_data = [x for x in non_insulation_materials if x["type"] == "flat_roof_vapour_barrier"]
        waterproofing_data = [x for x in non_insulation_materials if x["type"] == "flat_roof_waterproofing"]

        if (len(preparation_data_m2) != 2) or (len(vapour_barrier_data) != 1) or (
            len(waterproofing_data) != 1):
            raise ValueError("Incorrect number of data entries for non-insulation materials")

        # Break out the individual material costs
        preparation_m2_material_costs = sum([x["material_cost"] * floor_area for x in preparation_data_m2])
        vapour_barrier_material_costs = vapour_barrier_data[0]["material_cost"] * floor_area
        insulation_material_costs = material["material_cost"] * floor_area

        preparation_m2_labour_costs = sum([x["labour_cost"] * floor_area for x in preparation_data_m2])
        vapour_barrier_labour_costs = vapour_barrier_data[0]["labour_cost"] * floor_area

        # For waterproofing and upstand, we only have a total cost
        waterproofing_total_costs = waterproofing_data[0]["total_cost"] * floor_area

        labour_costs = preparation_m2_labour_costs + vapour_barrier_labour_costs
        labour_costs = labour_costs * self.labour_adjustment_factor

        materials_costs = preparation_m2_material_costs + vapour_barrier_material_costs + insulation_material_costs

        subtotal_before_profit = labour_costs + materials_costs + waterproofing_total_costs

        contingency_cost = subtotal_before_profit * self.FLAT_ROOF_CONTINGENCY
        preliminaries_cost = subtotal_before_profit * self.PRELIMINARIES
        profit_cost = subtotal_before_profit * self.PROFIT_MARGIN

        subtotal_before_vat = subtotal_before_profit + contingency_cost + preliminaries_cost + profit_cost
        vat_cost = subtotal_before_vat * self.VAT_RATE
        total_cost = subtotal_before_vat + vat_cost

        preparation_m2_labour_hours = sum([x["labour_hours_per_unit"] * floor_area for x in preparation_data_m2])
        vapour_barrier_labour_hours = vapour_barrier_data[0]["labour_hours_per_unit"] * floor_area
        waterproofing_labour_hours = waterproofing_data[0]["labour_hours_per_unit"] * floor_area

        labour_hours = preparation_m2_labour_hours + vapour_barrier_labour_hours + waterproofing_labour_hours

        # To install flat roof insulation, assume a small/medium project might be conducted by a team of 2-4.
        # We'll assume a team of 2 since a lot of the roofs will be on the smaller side and will review this later
        labour_days = (labour_hours / 8) / 2

        return {
            "total": total_cost,
            "subtotal": subtotal_before_vat,
            "vat": vat_cost,
            "contingency": contingency_cost,
            "preliminaries": preliminaries_cost,
            "material": materials_costs,
            "profit": profit_cost,
            "labour_hours": labour_hours,
            "labour_days": labour_days,
            "labour_cost": labour_costs
        }