A few thoughts from a distance. Noting that I have only briefly skimmed the official material, but did manage to read the executive summary. For clarity, the “Home” in the project title refers to an official methodology for “assessing the energy performance of dwellings” in the United Kingdom (that quote from the code repo preamble linked in the second URL above).
Reliance on a simulation‑based assessment methodology in this regulatory context seems generally workable and appropriate to me. So I am less skeptical than @Chris.Gordon-Smith on the general count of implementing regulations in code rather than through sets of prescribed calculations and accompanying technical standards.
The Home Energy Model methodology is being considered for use in binding legislation as well (consultation document, §3.1) and I presume that is the ultimate goal:
We are currently considering whether the open-source code could serve as the approved methodology for regulatory uses of the Home Energy Model (e.g. for Building Regulations compliance purposes). This would mean that the code replaces the specification document that has served this role for previous versions of SAP, and act as the ultimate legal reference for the methodology.
Stepping back, the concept of allowing building developers to submit their own thermal performance analysis for approval using simulation methods is not new. What is novel (as far as I am aware) is to offer an officially maintained simulation environment to facilitate that process and, moreover, to constitute its development as open source.
The choice of an open‑source MIT license is clearly useful. If not already covered in the GOV.UK plans, there needs to be an equal commitment to placing the calibration data and related information under Creative Commons CC‑BY‑4.0 licenses. Indeed, good software engineering suggests that the framework (code), the calibration data (empirical), sought energetic performance (prevailing and future policy criteria), and the instance data (often speculative) be kept separate, made public as appropriate, and suitably licensed per type.
GOV.UK suggests the methodology is intended to serve a number of roles and should accord users flexibility by separating the building physics from other more discretionary numerical and contextual aspects.
There is also to be some kind of ongoing quality process to confirm and improve the methodology and its applications. Questions arise as to who will determine which pull requests are accepted and how this shifting development will impact on the official status of the codebase/datasets? And, in particular, what will be the independence of the codebase maintainers? Stepping back, there are clearly some new statutory issues to traverse when adopting simulation‑based standards.
Here is the right place to make an oblique reference to the ongoing Horizon Post Office scandal in which important software was deemed “correct” by legal default.
Regarding the MIT license, python is not a compiled language, so third‑parties making forks will still need to distribute source as the means of circulating their modifications. So a permissive software license is appropriate, in my view. And as indicated earlier, the idea of forking is somewhat counter to the idea of having a single reference implementation to support statutory purposes.
The consultation documents are issued under an OGL‑UK‑3.0 license. Despite official claims to the contrary, I do not believe (nor am I alone) that that license is compatible with the CC‑BY‑4.0 license in either direction, inbound or outbound. It woud therefore be better to license all calibration data and related material under CC‑BY‑4.0 to enable its widest possible re‑use. Please note this point @Chris.Gordon-Smith. The doctrines and practicalities of open science should be uppermost.
The consultation documentation (the first URL above) suggests that “industry” is envisaged as the sole class of stakeholder. Given that most development in the openmod community takes place within academia, this seems to be an unnecessarily restrictive view.
The question of the standard patterns of usage arises. The sociology, if you like! Will there be some official set of standard occupant behaviors provided? And how will these various usage patterns be determined, validated, selected, and applied? This matter is particularly important because the methodology is to be also used for estimating carbon footprints and for tracking sector‑based progress towards net‑zero.
Similar remarks apply to the need for a nationwide inventory of building stock and associated characterizations. And again, under CC‑BY‑4.0 licensing for maximum re‑usability, assuming any privacy issues can be worked around in some technical way.
I guess the methodology will naturally update itself as the background climate data evolves (but not necessarily upwards) over time.
In the context of the noticeably increasing practice of conveying official regulations through reference software, it is worth noting that the Australian National Electricity Market (NEM) specification is defined using a model that only runs on the proprietary PLEXOS software. So the move here to open source in these circumstance is clearly laudable.
To underscore, it is paramount that the code, the data, including building stock and occupant inventories, and the policy and occupant behavior specifications are all under genuine open and interoperable licensing!
This openmod lightning talk (00:05:33) might provide some useful background: https://forum.openmod.org/t/vienna-2023-workshop-four-minute-lightning-talks/3622/20 And also the “built‑environment” tag on the forum too: https://forum.openmod.org/tag/built-environment
As a digression, I think that official agencies should abandon Twitter/X as a communication channel for public outreach. Twitter/X have not signed the European Commission’s voluntary code of conduct and commentators expect the Commission to take substantive action on legislative non‑compliance in due course (although admittedly under EU law).
Finally, others in the openmod might like to read the executive summary from the consultation document. The software design strategy, envisaged use‑cases, and rolling development approach (until somehow periodically frozen in legislation) are inspired. That said, there are quite a number of operational issues to resolve, particularly in relation to any mandated use in building performance standards.
HTH, R