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Technical reference

Technical References: Home Energy Model

The first Aeterno technical reference collection, covering the Home Energy Model (HEM) across 18 Technical Papers from climate data to system-level energy assessment.

About This Reference

This is Aeterno's technical reference for the Home Energy Model (HEM): the government's methodology for calculating the energy performance of dwellings. Each Technical Paper documents the inputs, calculation steps, assumptions, and outputs for a specific area of the model.

The reference is Aeterno's independent documentation of the government's Home Energy Model, written for engineers and energy assessors working with it.

How to Use This Reference

Use the sidebar navigation to jump to any Technical Paper. Each paper follows a consistent structure: Overview, Inputs, Calculation, Outputs, Assumptions, and Cross-references.

For notation and terminology, start with:

Document Structure

Reference Pages

PageDescription
Notation and ConventionsSymbols, units, and conventions
GlossaryKey terms and acronyms

Technical Papers

PaperTopic
TP-01: Overview and Climate DataExternal temperature, solar radiation, and wind speed inputs
TP-02: WrappersOrchestration layer coordinating all sub-models
TP-03: External ConditionsTemperature, wind, and solar irradiance processing
TP-04: Space Heating DemandHeat balance, internal gains, and heating schedules
TP-05: Fabric Heat LossU-values, thermal bridging, and element areas
TP-06: Ventilation and InfiltrationAir change rates, mechanical ventilation, and heat recovery
TP-07: Thermal MassThermal capacitance and dynamic heat storage
TP-08: Solar Gains and ShadingSolar irradiance, glazing transmission, and shading factors
TP-09: Hot Water DemandDaily draw-off profiles, temperature requirements, and distribution losses
TP-10: Pipework and Ductwork LossesDistribution system heat losses and gains
TP-11: Hot Water StorageCylinder losses, standing losses, and storage temperature profiles
TP-12: Heat PumpsCoP calculation, capacity, and system efficiency
TP-13: Storage HeatersCharge and discharge cycles, responsiveness, and efficiency
TP-14: BoilersEfficiency curves, part-load performance, and flue losses
TP-15: Heat BatteriesCharge cycles, storage capacity, and thermal output
TP-16: Heat EmittersRadiator output, underfloor heating, and emitter characteristics
TP-17: ControlsHeating control types, zoning, and setback temperatures
TP-18: PV and BatteryPV generation, battery charge/discharge, and self-consumption

Why HEM on Your Real Data Matters

Every HEM rating produced today rests on surveyed assumptions: U-values from age bands, infiltration rates from construction type, heat pump performance from data sheets. A rating grounded in measured reality is a different number. HeatAssure™, from Aeterno, keeps one governed record per home and checks what was delivered against what was promised as evidence arrives. Learn more

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