OpenPH-Demand

Energy demand calculations for Passive House (PHPP)

Part of the openph UV workspace - implements PHPP energy demand calculations with exact numerical fidelity to Excel PHPP.

Purpose

OpenPH-Demand calculates:

• Annual Heating Demand: Transmission and ventilation heat losses, internal/solar gains
• Annual Cooling Demand: Solar gains, internal gains, cooling strategies
• Solar Radiation: Window and opaque surface solar radiation for heating/cooling periods
• Ground Heat Transfer: Temperature calculations for ground-coupled surfaces

It does not yet implement the PHPP Heating load / Cooling load worksheets — only the peak-load climate inputs those worksheets consume. So there is no design-load (W) result, and the energy demand summary reports peak_w: null rather than a misleading zero.

Structure

openph-demand/
├── src/
│   └── openph_demand/
│       ├── heating_demand/      # Heating demand calculations
│       ├── cooling_demand/      # Cooling demand calculations
│       ├── ground/              # Ground heat transfer
│       ├── solar/               # Solar radiation calculations
│       ├── to_table/            # Table view renderers
│       ├── summary.py           # EnergyDemandSummary + build_energy_demand_summary
│       ├── get_solvers.py       # Type-safe solver accessors
│       └── solvers.py           # Solver classes (Energy, Ground, Solar)
├── tests/
└── pyproject.toml

Usage

from openph.phpp import OpPhPHPP
from openph_demand.get_solvers import (
    get_openph_energy_demand_solver,
    get_openph_ground_solver,
    get_openph_solar_solver,
)

# Create PHPP model
phpp = OpPhPHPP()

# Get solvers (registered via entry points)
energy_solver = get_openph_energy_demand_solver(phpp)
ground_solver = get_openph_ground_solver(phpp)
solar_solver = get_openph_solar_solver(phpp)

# Access demand calculations
heating_demand = energy_solver.heating_demand
cooling_demand = energy_solver.cooling_demand

# Get results -- read the canonical annual scalars; never sum a monthly row
annual_heating_kwh = heating_demand.total_yearly_heating_demand              # Heating!AF117
annual_heating_kwh_m2a = heating_demand.total_yearly_specific_heating_demand  # Heating!Q78
annual_cooling_kwh = cooling_demand.total_annual_cooling_demand_kwh           # Cooling!AG155
ground_temps = ground_solver.periods
window_radiation = solar_solver.annual_demand

Energy Demand Summary

For an application — a web request, a batch parametric run, a stored record — use the compact summary rather than reading solver properties one at a time:

from openph_demand import build_energy_demand_summary

summary = build_energy_demand_summary(phpp)
payload = summary.to_dict()   # JSON-ready
text = summary.to_json()      # stable ordering, no NaN/Infinity

{
  "schema_version": "1.0",
  "floor_area_m2": 307.40378,
  "heating": {
    "annual_kwh": 7092.797,
    "annual_kwh_m2a": 23.073228,
    "monthly_kwh": [{"period": "jan", "value": 1552.683}, "…"],
    "peak_w": null
  },
  "cooling": {"annual_kwh": 1769.475, "annual_kwh_m2a": 5.756192, "…": "…"},
  "warnings": [],
  "engine_versions": {"openph": "0.6.0", "openph-demand": "0.6.0", "PHX": "1.56.82"}
}

What it is, and is not:

• It supplements openph.results.collect_results — the complete, PHPP-addressable audit document — and does not replace or shrink it. The summary is ~200x smaller and carries no worksheet addresses.
• Annual values are canonical PHPP results, not sums the builder computed. Callers must not re-aggregate monthly_kwh.
• Monthly values carry "jan"…"dec" period labels; array position is never the contract.
• null means "OpenPH does not calculate this quantity", never zero. That is why peak_w is null today.
• cooling is sensible useful cooling demand and excludes dehumidification — it is not the combined PHI Verification!I39 figure.
• schema_version is independent of the package version. A reader accepts any matching major version, so additive 1.x fields stay readable.
• No pandas, no rich: the summary is core output, not a table view.

Registered Solvers

This package registers three solver plugins with OpenPH:

• energy_demand → OpPhEnergyDemandSolver (heating + cooling)
• ground → OpPhGroundSolver (ground heat transfer)
• solar_radiation → OpPhSolarRadiationSolver (solar gains)

Development

Part of UV workspace - see root context/ENVIRONMENT.md:

uv sync                           # Install all workspace packages
uv run pytest openph-demand/tests/ # Run tests