Methodology.
What backs each number, and what does not.
What this documents
This page documents the DGH Climate Engine at version 0.2.0. Every number the engine publishes carries that version in its payload, and this page states what the version means.
The address /methodology is permanent. It carries no version segment and never will: a citation made today resolves after the engine moves on, so the version is stated here in the text rather than in the path.
Two layers, one engine
The engine is not one thing. The state math and the greenhouse model rest on different kinds of evidence, and publishing them as one authority would overclaim. Every payload therefore carries a machine-readable layer and a validation_status, and this page states the same split in words.
The psychrometric core — psychrometric-core, validated
The state math is asserted against 840 psychrolib parity fixtures with a documented tolerance per property, across five property suites, with one stated domain limit: the fog path does not close below freezing, and that limit is written down rather than tolerated. The equations are ASHRAE Fundamentals 2017 chapter 1, numbers 3, 5, 6, 20, 26, 30, 33 and 35. This layer is citable today.
The greenhouse model — greenhouse-model, design-stage
Every coefficient in the transform namespace is provisional and has never been engineering-reviewed. Four of them belong to DGH and carry no citation at all: comfort.blend.dayFullWM2, comfort.temperature.damageMarginK, transform.screenTransmission and transform.design.ventCapacityAch. The document says so rather than dressing them as literature.
The sensitivity is measured rather than asserted. Moving transform.canopyTranspirationFraction from 0.50 to 0.70 changes the ventilated rise at 30 ACH by 1.9 K — about one envelope half-width, which is enough to move a verdict.
The provisional flags are the authority, not a weakness to tidy away. A model gets cited for being checkable, not for being certain, and a design-stage layer that says so stays usable where one claiming validation it has not earned would not.
The one coefficient that decides a headline verdict
strategy.fog.approachK is an owner decision rather than a literature value. It sets the floor of the fog rung at the outdoor wet-bulb temperature plus the approach, and it ships at 3.0 K.
Its consequence is measured. Swept from 0.5 K to 6.0 K in 0.5 K steps against the four acceptance climates, three never move: Dubai grades above at every value, Beja grades inside at every value, and Naaldwijk grades inside at every value. Riyadh crosses exactly once.
On vent and fog, the Riyadh 24-hour mean runs 22.2 °C at the shipped 3.0 K, 23.7 °C at a 4.5 K approach and 24.2 °C at a 5.0 K approach — graded inside up to 4.5 K and above from 5.0 K. The shipped value sits on the workable side of that boundary.
The crossing is published rather than tuned away. Whoever revises this leaf should know which story they are moving before they move it, and a coefficient whose boundary is hidden is a coefficient nobody can review.
The caveat every verdict carries
Indicative, design-stage. Engineering confirms.
That sentence travels with every verdict the engine emits. It is one constant quoted everywhere rather than a phrase each surface rewrites, so a payload, a tool response and this page cannot state the same limit three different ways.
Licence and citation
Apache-2.0 covers the software implementation and only that. The license field on every payload names its own scope as software-implementation, so the scope word on this page is the scope word in the data. The licence text sits at https://www.apache.org/licenses/LICENSE-2.0.
The crop and greenhouse parameter database is not licensed. No data grant has been made. The software licence names the licence of the code that computed a number, which is a true and precise statement about the code and says nothing about the parameter database or about the numbers derived from it; a consumer must not read it as a grant over either.
How to cite
DutchGreenhouses B.V. (2026). DGH Climate Engine v0.2.0. Apache-2.0.
Credit line: DutchGreenhouses® — DGH Climate Engine
Sources
The engine cites methods where it applies them and cites nothing it does not apply. Four keys travel with every payload:
plant_empowerment— Geelen, Voogt & van Weel — Plant Empowerment: The Basic Principles.bakker_1995— Bakker et al. — Greenhouse Climate Control: An Integrated Approach (1995).ashrae_2017— ASHRAE Handbook — Fundamentals (2017), chapter 1.dgh_crop_model_db— The DGH Crop Model Database.
The licence-restricted calibration layer the crop store withholds contributes no key here and is never read. Its figures are not published; what gets published is the DGH model's own output for the location asked about.
Version history
The version bumps on any change that moves a published number. A coefficient revision is such a change and so is a correction to an equation branch; a comment change is not. This address does not move when the version does.
- 0.2.0 — 2026-08-16. Every payload carries its provenance: licence, attribution, citation, engine name and engine version — plus the epistemic split as a machine-readable layer and validation_status. 66 barrel exports.
- 0.1.0 — 2026-08-15. The engine lands as a library nothing imports: psychrometric state, crop comfort, the strategy ladder, the greenhouse transform, the 24-hour balance and the state language. 58 barrel exports.