How We Calculate Your Passport Health Score
The public 0β100 score is now the Home Resilience Passport Health Score: a transparent 4-pillar composite built from canonical facts, evidence, verification level, and a deterministic energy engine.
- 01 4 locked pillars: Energy Performance (40%), Resilience Coverage (25%), Verification Quality (20%), Improvement Momentum (15%)
- 02 Energy Performance is powered by the six-component energy engine: envelope, heating, ventilation, hot water, solar, and storage/grid
- 03 Every Passport fact carries source, confidence, timestamp, and verification status
- 04 Market depth varies: UK records and adapters are strongest today; other markets are expanding with explicit readiness labels
- 05 The coming AI Resilience Agent will guide evidence gathering and next-best actions, but deterministic scoring remains the trust layer
How the 0β100 Passport Health Score Works (v1)
The Passport Health Score is a continuous 0β100 metric that updates as the home's facts, evidence, and improvements evolve. It is not just an energy score: it combines performance, resilience, trust, and progress.
The Passport is the memory layer, the deterministic engine is the trust layer, and the AI Resilience Agent is the coming guidance layer. The Agent can explain and prioritize, but it does not override verified facts or physics-based calculations.
Energy Performance
Envelope, systems, solar, storage, and grid-flexibility signals from official records, modelled inputs, and confirmed facts.
Resilience Coverage
Climate and home-readiness signals such as flood risk, overheating risk, local adapter readiness, and future resilience facts.
Verification Quality
How trustworthy and recent each Passport fact is: inferred, user-confirmed, document-supported, scan-supported, or contractor-verified.
Improvement Momentum
Credit for completed and verified upgrades, with stronger signals when improvements are recent and evidence-backed.
Passport Facts First
The score is computed from the canonical Passport registry. Facts can be inferred, user-confirmed, scan-supported, document-supported, or contractor-verified.
Deterministic Weighting
The four pillars are combined with locked v1 weights. Each pillar exposes its explanation and supporting data instead of hiding logic in a black box.
Guidance Layer Coming Next
The AI Resilience Agent direction is to ask for missing evidence, explain tradeoffs, and suggest next-best actions. It is not treated as the scoring authority.
Energy Performance Engine: 6 Component Breakdown
These six components feed the 40% Energy Performance pillar. They are not separate top-level Passport weights; they are the internal energy model used inside the broader Health Score.
Envelope
Assesses insulation, airtightness, and thermal bridging of walls, roof, floors, and windows.
β U-values are inferred from text descriptions, not measured. This is heuristic, not a full SAP fabric calculation.
Data Sources
- EPC (U-value descriptions β lookup table)
- Airtightness from EPC when present (defaults to ACH50=10)
- SAP 10.2 (benchmark ranges)
- OSM geometry (when available for bridging estimate)
Heating
Evaluates heating system type and efficiency, including boilers, heat pumps, and distribution.
β Rule-based keyword matching from EPC descriptions. Not a full plant simulation.
Data Sources
- EPC (system type, descriptors)
- COP band mapping (ASHP/GSHP)
- Weather compensation / low-flow bonus flags
Ventilation
Measures air quality systems and heat recovery efficiency.
β Rule-based scoring. MVHR efficiency is banded, not measured.
Data Sources
- EPC (vent type field)
- MVHR efficiency band mapping
Water
Analyses hot water heating system type and efficiency.
β Pattern-matched from EPC descriptions.
Data Sources
- EPC (hot water field)
- HPWH / stratified tank / DWHR pattern matching
Solar
Calculates on-site renewable generation based on enriched data and system flags.
β Without a full demand profile, solar utilisation is estimated from defaults. Generation data requires PVGIS enrichment.
Data Sources
- PVGIS (solar irradiance + annual generation)
- EPC (existing PV flag)
- DC coupling / bifacial / tracker flags
Storage / Grid
Evaluates battery storage, grid flexibility, and virtual power plant participation.
β Capability score, not a verified operational optimisation model.
Data Sources
- Battery capacity bands
- VPP participation flag
- TOU optimisation flag
- Thermal storage flag
Our Technology Database
Roughly 80 technologies researched so far across 7 categories. We keep adding as we learn what actually works in real homes.
Envelope and Insulation
35 technologies
Heating and Cooling
45 technologies
Ventilation and Air Quality
20 technologies
Water Heating and Efficiency
15 technologies
Renewables and Solar
25 technologies
Storage and Grid Integration
35 technologies
Smart Controls and Automation
25 technologies
Energy Scoring Curves Explained
Inside the Energy Performance pillar, each metric maps to a 0β100 sub-score using smooth curves. Small improvements always count, and gains naturally taper at the high end β just like real-world energy physics.
U-Value β Score (Envelope)
Lower U-values (better insulation) yield higher scores via a sigmoid curve. Example: Wall U-0.18 (R-31) scores ~85, improving to U-0.12 (R-47) reaches 95.
COP β Score (Heating)
Heat pump efficiency on a linear-to-exponential curve. ASHP COP 3.5 scores 70, 4.3 scores 90; GSHP 4+ can exceed 95.
Other Examples
- MVHR recovery: 90% β 80 score, 95% β 95 score
- Battery self-consumption: 30% β 40 score, 60% β 85 score
- Solar yield: Normalized to roof potential via PVGIS
Climate-Relative Rank
Your score report includes a climate-relative rank that compares your home against similar properties in the same climate zone, region, and building type. This is an additive context layer β it does not change the Passport Health Score.
β Important: this comparison is modeled, not empirical
The distributions used for ranking are synthetic β derived from building stock data (UK EPC register, NREL ResStock for US, IS 5281 norms for Israel). They are not computed from real user scores in this system. Ranks are never described as percentiles; they use named tiers to avoid false precision.
How Cohorts Work
Your home is placed in a cohort defined by:
- Climate band β simplified KΓΆppen-Geiger from your coordinates (e.g. temperate, cold, mediterranean)
- Region β UK, US, or IL (distributions differ per country)
- Property type β flat, terrace, semi, detached
- Floor area band β small (<70mΒ²), medium, large, very-large
Example cohort key: temperate:UK:semi:medium
Tiers, Not Percentiles
- LeadingTop ~10% of modeled cohort
- Above averageTop 10β35%
- TypicalMiddle 35β65%
- Below averageBottom 35β65% (15β35th)
- LaggingBottom ~15%
Data confidence: UK = high (EPC register), US = medium (ResStock), IL = low (code norms). Confidence is shown alongside your rank.
Unsupported countries currently return a note asking where you're scoring from so we know which markets to expand next.
Potential Score: Likely vs Stretch
Alongside your current score, we show a potential range β what the Energy Performance pillar and overall Passport Health Score could reach with targeted improvements.
Likely
Top 3 high/medium-confidence recommendations applied to your current score. Represents a realistic improvement from 2β3 targeted upgrades. Capped at 95.
Stretch
Top 6 feasible recommendations applied (including caveated ones; excludes infeasible). Represents the outer bound if all practical measures are pursued. Capped at 98.
β Potential is bundle simulation, not a certified forecast
Score impact values in our recommendation catalog are manually assigned estimates β not derived from physics calculations or SAP. Interaction effects between co-installed measures are not modelled. Treat the range as directional, not as a guaranteed savings figure.
Beyond Net Zero: Buildings as Batteries
Our goal is to help every home become better at using, generating, storing, and sharing energy. In the Energy Performance pillar, 100 represents a home that is genuinely energy-positive and useful to the grid β not just βnet zeroβ on paper.
An Energy Performance score of 100/100 represents an energy-positive prosumer home β one that generates approximately 6,000 kWh/year from solar while consuming only 4,000 kWh, resulting in a net export of roughly β2,000 kWh/year for a typical UK 3-bed semi. The overall Passport Health Score also requires resilience coverage, verification quality, and improvement momentum.
Thermal Mass as Storage
Buildings store energy as heat in walls, floors, and thermal mass β free batteries that need no chemistry. Hedar et al. (2023, Building Simulation) quantified this: homes provide grid flexibility through thermal inertia, pre-heating or pre-cooling during cheap/clean grid windows and coasting through peaks. Our score rewards homes with high thermal mass and smart scheduling capability.
Heat Pumps for Load Shifting
A heat pump paired with a well-insulated building envelope is a controllable thermal load. Power-to-Heat during surplus renewable periods stores energy in the building fabric itself. On Octopus Agile or similar dynamic tariffs, a smart ASHP can run predominantly on cheap overnight electricity, shifting kilowatt-hours from grid-stress periods to off-peak abundance.
Solar + Battery + V2G
Rooftop solar generates. A home battery (10β20 kWh) stores and time-shifts. Vehicle-to-Grid (V2G) adds 40β80 kWh of EV battery into the equation. Together, these create a system that can island during grid stress events and sell power back at peak prices β turning household energy into a revenue stream rather than a cost centre.
Every Home as a VPP Node
A single prosumer home is interesting. One million of them, coordinated via demand response APIs, form a virtual power plant (VPP) that can provide gigawatt-scale grid balancing services. The Energy Performance pillar is designed to track and reward each home's contribution potential β not just its own consumption efficiency.
What Energy Performance 100 Actually Means
(UK 3-bed semi)
vs 4,000 kWh consumed
prosumer asset
Research basis: Hedar et al. (2023) "Buildings as Batteries: Leveraging Thermal Inertia for Grid Flexibility," Building Simulation journal. Heat pump Power-to-Heat storage validated against UK Climate Change Committee demand flexibility estimates.
What is heuristic vs live vs planned
Live (actively used in the Passport Health Score)
- 4-pillar Passport weighting: Energy, Resilience, Verification, Momentum
- Canonical Passport facts with source, confidence, timestamp, and verification status
- EPC fabric descriptions β U-value lookup β Energy Performance component score
- EPC system type fields β rule-based Energy Performance component scores
- Airtightness from EPC when present
- PVGIS solar generation when enriched
- Storage/grid capability flags (battery, VPP, TOU)
- Climate-relative rank (v2.3, modeled distributions)
Heuristic (in use, but approximate)
- U-value inference from EPC text (not measured)
- COP scoring from qualitative descriptors
- Thermal bridging default junction count
- Potential score impact values (manually assigned)
- Confidence / uncertainty (completeness-based, not error-calibrated)
- Climate rank distributions (synthetic, not from real user scores)
Planned (not yet live scoring authority)
- AI Resilience Agent for evidence gathering, explanations, and next-best actions
- Smart meter time-series calibration
- Full OSM geometry coupling in every score
- Thermal-camera / retrofit proof ingestion
- Calibrated uncertainty from real measured error
- Public contribution pipeline for model updates
Known limitations (current model)
- Some component mappings are still rule-based and text-driven.
- Confidence and uncertainty are estimated from input completeness, not measured calibration error.
- Validation dataset includes both measured and benchmark archetypes; measured sample is still small.
Our Open Methodology Commitment
Everything here is open. Full formulas, weights, and update logs are in the repo. We believe energy scoring should be auditable β not a black box. Where something is heuristic, we say so.