EnergyPlus Building Simulation (.idf, .epjson)

@modelscript/energyplus (languages/energyplus) provides compiler, thermal lumped-capacitance DAE lowering, and bidirectional TGG synchronization for US Department of Energy (DOE) EnergyPlus building energy and HVAC models.

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Supported Extensions & Standards

Extension	Format	Description
.idf	EnergyPlus Input Data File	Industry-standard comma/semicolon delimited building simulation deck
.epjson	EnergyPlus JSON Schema	Structured JSON schema representation of EnergyPlus models

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Key Capabilities

1. Lumped-Capacitance Multi-Zone Thermal DAEs

• Translates architectural thermal zones and building envelopes into continuous energy balance DAEs:$$C_{z,i}\frac{d{T}_{z,i}}{dt}=\sum _j{\dot{Q}}_{\text{cond},ij}+\sum _k{\dot{Q}}_{\text{conv},ik}+{\dot{Q}}_{\text{solar}}+{\dot{Q}}_{\text{internal}}+{\dot{Q}}_{\text{HVAC}}$$
• Envelope Conduction: Multi-layer wall, floor, and roof constructions with layer-resolved thermal conductivity $k$, density $\rho$, and specific heat $c_p$.
• Window & Fenestration Optics: U-factor, Solar Heat Gain Coefficient (SHGC), and visible transmittance shading calculations.
• Internal Loads: Schedules for lighting, occupancy sensible/latent heat release, and plug-load equipment dissipation.

2. Direct DAE Lowering

• Compiles building geometry and HVAC schedules directly into @modelscript/runtime's DAEBuilder linear memory arena, enabling co-simulation with dynamic grid power models (@modelscript/pscad) and district energy networks.

3. Bidirectional Triple Graph Grammar (TGG) Sync

• Implements bidirectional TGG rules (energyplus-sync.ts) synchronizing EnergyPlus thermal zones with:
  • Modelica (Modelica.Thermal / IBPSA Buildings): Automatic translation into acausal thermal components and fluid loops.
  • STEP CAD (ISO 10303): Validates physical geometric volume and boundary surface areas against 3D architectural CAD envelopes.

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Static Analysis & Pre-Flight Linter Rules

8 rules6 error2 warning Run with msx energyplus lint

Code	Rule	Severity	Message
M7901	unmatched-interzone-surface	error	Interzone surface '<surfName>' in zone '<zoneName>' specifies outside boundary object '<targetSurf>' which does not exist or has mismatched reciprocal boundary.
M7902	non-convex-surface-polygon	warning	Surface polygon '<surfName>' in zone '<zoneName>' violates planar convexity, which may impair solar raytracing and view factor calculations.
M7903	missing-thermal-properties	error	Material '<matName>' has non-positive thermal property '<prop>' (<val>), violating second law of thermodynamics.
M7904	unconnected-hvac-zone	error	HVAC component '<hvacName>' references non-existent thermal zone '<zoneName>'.
M7905	excessive-surface-absorption	warning	Material '<matName>' has solar absorptance coefficient <value>, which exceeds the physical maximum of 1.0.
M7906	duplicate-zone-name	error	Duplicate thermal zone identifier '<zoneName>' detected in building model.
M7907	unreferenced-construction	error	Building surface '<surfName>' references undefined construction '<constName>'.
M7908	zero-thickness-material	error	Opaque material '<matName>' has invalid non-positive thickness (<value>m).

Generated from languages/energyplus/src/lints/rules.ts. All languages →

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CLI Usage

# Lint an EnergyPlus building model deck
msx energyplus lint CommercialOffice.idf

# Lower thermal zones to ModelScript linear memory DAE arena
msx energyplus to-dae CommercialOffice.idf --out=office.dae.json

# Project into standard Modelica IBPSA Buildings library components
msx energyplus to-modelica CommercialOffice.idf -o BuildingThermalModel.mo