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334 lines
14 KiB
Python
334 lines
14 KiB
Python
import math
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from typing import List
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from datatypes.enums import QuantityUnits
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from backend.Property import Property
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from BaseUtility import Definitions
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from recommendations.recommendation_utils import (
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r_value_per_mm_to_u_value, calculate_u_value_uplift, is_diminishing_returns, update_lowest_selected_u_value,
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get_recommended_part, get_wall_u_value
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)
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from recommendations.config import PARTIALLY_FILLED_PERCENTAGE_ASSUMPTION
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from utils.logger import setup_logger
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logger = setup_logger()
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class WallRecommendations(Definitions):
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YEAR_WALLS_BUILT_WITH_INSULATION = 1990
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# After 1930, Solid brick walls became less populate and instead, cavity walls became a
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# more popular choice
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YEARS_CAVITY_WALLS_BEGAN = 1930
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U_VALUE_UNIT = 'w/m-¦k'
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# part L building regulations indicate that any rennovations on an existing property's walls should
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# achieve a U-value of no higher than 0.3
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# This can be seen in table 4.3 in building regulations part L:
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# https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1133079
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# /Approved_Document_L__Conservation_of_fuel_and_power__Volume_1_Dwellings__2021_edition_incorporating_2023_amendments.pdf
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BUILDING_REGULATIONS_PART_L_MAX_U_VALUE = 0.3
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# We don't recommend measures that are too low because it becomes expensive, therefore we aim to avoid
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# diminishing returns. This value should be verified with Osmosis (TODO)
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DIMINISHING_RETURNS_U_VALUE = 0.25
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# Building regulations part L also indicates that cavity wall insulation should result in 0.55 u-value
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BUILDING_REGULATIONS_PART_L_CAVITY_WALL_MAX_U_VALUE = 0.55
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# Part L regulations indicate that any new build should have walls that achieve a u-value of no higher
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# than 0.18.
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BUILDING_REGULATIONS_PART_L_NEW_BUILD_MAX_U_VALUE = 0.18
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# 0.15 is an often cited diminishing returns value for new builds
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NEW_BUILD_DIMINISHING_RETURNS_U_VALUE = 0.15
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# Add some error so that if, for example, a new part we recommend provides a u-value of 0.19,
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# we still consider it as an option
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U_VALUE_ERROR = 0.01
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def __init__(
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self,
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property_instance: Property,
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materials: List
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):
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self.property = property_instance
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# For audit purposes, when estimating u values we'll store it
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self.estimated_u_value = None
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# Will contains a list of recommended measures
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self.recommendations = []
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self.materials = materials
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@property
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def ewi_valid(self):
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"""
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This method check available data, to determine if a property is suitable for external wall insulation
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"""
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# Current logic: If the property is in a conservation area/heritage building/listed building or a flat,
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# it is not suitable for EWI
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if self.property.restricted_measures or (self.property.data["property-type"].lower() == "flat"):
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return False
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return True
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def recommend(self):
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# if building built after 1990 + we're able to identify U-value +
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# U-value less than 0.18 and if in or close to a conversation area,
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# recommend internal wall insulation as a possible measure
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u_value = self.property.walls["thermal_transmittance"]
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is_cavity_wall = self.property.walls["is_cavity_wall"]
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insulation_thickness = self.property.walls["insulation_thickness"]
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# We check if the wall is already insulated and if so, we exit
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if (insulation_thickness in ["average", "above average"]) or self.property.walls["is_filled_cavity"]:
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return
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if u_value:
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if self.property.walls["thermal_transmittance_unit"] != self.U_VALUE_UNIT:
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raise NotImplementedError("Haven't handled the case of other u value units yet")
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# We can't detect it's a cavity wall, but it was built after 1990 so likely built with insulation already
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# + it already has a U-value WORSE than the building regulations, so we recommend either internal or
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# external wall insulation
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if (not is_cavity_wall) and (self.property.year_built >= self.YEAR_WALLS_BUILT_WITH_INSULATION) and (
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u_value >= self.BUILDING_REGULATIONS_PART_L_MAX_U_VALUE
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):
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# Recommend insulation
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self.find_insulation(u_value)
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return
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# We can't detect it's a cavity wall, but it was built after 1990 so likely built with insulation already
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# + it already has a U-value better than the building regulations, so we don't need to recommend anything
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if (not is_cavity_wall) and (self.property.year_built >= self.YEAR_WALLS_BUILT_WITH_INSULATION) and (
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u_value <= self.BUILDING_REGULATIONS_PART_L_MAX_U_VALUE
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):
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# Recommend nothing
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return
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raise NotImplementedError("Not implemented yet")
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u_value = get_wall_u_value(
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clean_description=self.property.walls["clean_description"],
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age_band=self.property.age_band,
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is_granite_or_whinstone=self.property.walls["is_granite_or_whinstone"],
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is_sandstone_or_limestone=self.property.walls["is_sandstone_or_limestone"],
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)
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self.estimated_u_value = u_value
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if is_cavity_wall:
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if u_value >= self.BUILDING_REGULATIONS_PART_L_MAX_U_VALUE:
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# Test filling cavity
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self.find_cavity_insulation(u_value, insulation_thickness)
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return
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# Remaining wall types are treated with IWI or EWI
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if u_value >= self.BUILDING_REGULATIONS_PART_L_MAX_U_VALUE:
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self.find_insulation(u_value)
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return
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# If the u-value is within regulations, we don't do anything
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return
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def find_cavity_insulation(self, u_value, insulation_thickness):
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"""
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This method tests different materials to fill the cavity wall, determining which
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material will give us the best U-value.
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We check for diminishing returns, however this function does not check for meeting building
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Part L regulations right now. This is because Part L is less stringent for cavity walls
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Width of a cavity:
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There are various sources online that suggest the width of a cavity wall is around 50mm. The retrofit course
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indicates that most cavities are 50-75mm. Many sources online indicate that 50mm is the standard MINIMUM figure
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therefore we'll use 75mm as the base assumption
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This document:
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https://www.buildingcentre.co.uk/media/_file/pdf/22220_pdf27.pdf
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Indicates that they could be 50-85mm wide
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:param u_value: u_value of the starting wall
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:param insulation_thickness: describes the insulation level of the wall. If "below average", we have a partially
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filled cavity wall
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"""
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cavity_wall_fills = [m for m in self.materials if m["type"] == "cavity_wall_insulation"]
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cavity_width = 75
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if insulation_thickness == "below average":
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cavity_width = cavity_width * (1 - PARTIALLY_FILLED_PERCENTAGE_ASSUMPTION)
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# Test the different fill options
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lowest_selected_u_value = None
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recommendations = []
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for part in cavity_wall_fills:
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part_u_value = r_value_per_mm_to_u_value(cavity_width, part["r_value_per_mm"])
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_, new_u_value = calculate_u_value_uplift(u_value, part_u_value)
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new_u_value = math.ceil(new_u_value * 100.0) / 100.0
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if is_diminishing_returns(
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recommendations, new_u_value, lowest_selected_u_value, self.DIMINISHING_RETURNS_U_VALUE
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):
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continue
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if new_u_value <= self.BUILDING_REGULATIONS_PART_L_CAVITY_WALL_MAX_U_VALUE:
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lowest_selected_u_value = update_lowest_selected_u_value(lowest_selected_u_value, new_u_value)
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estimated_cost = part["cost"] * self.property.insulation_wall_area
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recommendations.append(
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{
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"parts": [
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get_recommended_part(
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part=part,
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selected_depth=None,
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quantity=self.property.insulation_wall_area,
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quantity_unit=QuantityUnits.m2.value,
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selected_total_cost=estimated_cost
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)
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],
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"type": "wall_insulation",
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"description": f"Fill cavity with {part['description']}",
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"starting_u_value": u_value,
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"new_u_value": new_u_value,
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"sap_points": None,
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"cost": estimated_cost,
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}
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)
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self.recommendations = recommendations
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def _find_insulation(self, parts, u_value):
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lowest_selected_u_value = None
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recommendations = []
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for part in parts:
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for depth, cost_per_unit in zip(part["depths"], part["cost"]):
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part_u_value = r_value_per_mm_to_u_value(depth, part["r_value_per_mm"])
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_, new_u_value = calculate_u_value_uplift(u_value, part_u_value)
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new_u_value = math.ceil(new_u_value * 100.0) / 100.0
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# If I have a lowest U value and my new u value is higher than that but lower than the
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# diminishing returns threshold, it can be considered
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# If I have a lowest U value and my new u value is lower than the lowest value, it's
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# further into the diminishing returns threshold and can shouldn't be
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if is_diminishing_returns(
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recommendations, new_u_value, lowest_selected_u_value, self.DIMINISHING_RETURNS_U_VALUE
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):
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continue
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# We allow a small tolerance for error so we don't discount the recommendation entirely
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if new_u_value <= self.BUILDING_REGULATIONS_PART_L_MAX_U_VALUE:
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lowest_selected_u_value = update_lowest_selected_u_value(lowest_selected_u_value, new_u_value)
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estimated_cost = cost_per_unit * self.property.insulation_wall_area
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recommendations.append(
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{
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"parts": [
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get_recommended_part(
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part=part,
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selected_depth=depth,
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quantity=self.property.insulation_wall_area,
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quantity_unit=QuantityUnits.m2.value,
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selected_total_cost=estimated_cost
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)
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],
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"type": "wall_insulation",
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"description": "Install " + self._make_description(part, depth),
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"starting_u_value": u_value,
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"new_u_value": new_u_value,
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"sap_points": None,
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"cost": estimated_cost,
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}
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)
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return recommendations
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def find_insulation(self, u_value):
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"""
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This function contains the logic for finding potential insulation measures for a property, depending
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on the parts available and whether the property can have external wall insulation installed
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:return:
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"""
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ewi_parts = [
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part for part in self.materials if part["type"] == "external_wall_insulation"
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] if self.ewi_valid else []
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iwi_parts = [part for part in self.materials if part["type"] == "internal_wall_insulation"]
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# Recommend external and internal wall insulation separately
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# Since external and internal wall insulation are sufficiently different,
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# we separate the logic for for recommending them, therefore we don't
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# consider diminishing returns between the two
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ewi_recommendations = self._find_insulation(ewi_parts, u_value)
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iwi_recommendations = self._find_insulation(iwi_parts, u_value)
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self.recommendations += ewi_recommendations + iwi_recommendations
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self.prune_diminishing_recommendations()
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@staticmethod
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def _make_description(part, depth):
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return f"{depth}{part['depth_unit']} {part['description']}"
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def prune_diminishing_recommendations(self):
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# For any recommendations, if we have at least 1 reommendation that does not exhibit diminishing returns
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# we trim all others that are beyond the diminishing returns threshold
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# We first check if we have any recommendations that are not diminishing returns
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not_diminishing_return = [
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rec for rec in self.recommendations if rec["new_u_value"] >= self.DIMINISHING_RETURNS_U_VALUE
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]
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if not_diminishing_return:
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self.recommendations = [
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rec for rec in self.recommendations if rec["new_u_value"] >= self.DIMINISHING_RETURNS_U_VALUE
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]
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@staticmethod
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def rvalue_per_mm(total_r_value: float, thickness_mm: float) -> float:
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"""Return R-value per mm.
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Parameters
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----------
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total_r_value : float
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Total R-value (in m2K/W).
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thickness_mm : float
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Thickness of the material in mm.
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Returns
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-------
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float
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R-value per mm.
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"""
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return total_r_value / thickness_mm
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@staticmethod
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def thermal_conductivity_to_r_value_per_mm(thermal_conductivity: float) -> float:
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"""Convert thermal conductivity to R-value per mm.
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Parameters
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----------
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thermal_conductivity : float
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Thermal conductivity (in W/mK).
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Returns
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-------
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float
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R-value per mm.
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"""
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# Calculate R-value in m²K/W for 1 meter of the material
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r_value_per_meter = 1 / thermal_conductivity
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# Convert R-value to R-value per mm
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r_value_per_mm = r_value_per_meter / 1000
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return r_value_per_mm
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