<div dir="ltr"><div><p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>Hi Chris,</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">You’ve raised an important—and frankly unavoidable—question
for anyone working in building simulation, NatHERS, LEED, or broader
performance modelling:</p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>If an LLM can rapidly generate the <i>appearance</i> of a
complete modelling package, what happens to the value of the modeller?</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">As someone who actively uses LLMs (ChatGPT) to support the
production of reports—particularly complex Performance Solutions and NatHERS
documentation—I see both the opportunity <i>and</i> the real risk.</p>
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<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>The Risk: “Autocorrect on Steroids” Can Mimic Output
Without Doing the Work</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">You’re right: LLMs can now generate</p>
<ul style="margin-top:0cm;margin-bottom:0cm" type="disc">
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">unmet
load tables,</li>
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">calibration
summaries,</li>
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">error
logs,</li>
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">and
even plausible-looking LEED or NCC/NatHERS documentation,</li>
</ul>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>all without any underlying simulation ever being run.</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">This creates two exposures:</p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>1. Reviewers may not detect fabricated modelling
artefacts</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">Even experienced certifiers can struggle to identify
fabricated tables if they are numerically plausible.<br>
NCC and NatHERS documentation is especially vulnerable because reports often
follow rigid templates.</p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>2. The modelling profession risks being judged by its
paperwork, not its competence</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">If the visible output (the report) becomes easily faked,
then the <i>perceived value</i> of modelling may degrade—even though the true
value is in the physics, domain reasoning, and regulatory interpretation behind
the scenes.</p>
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<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>So what is the value a competent modeller still provides?</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">Fundamentally:</p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>1. Understanding the physics and constraints</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">LLMs can <i>describe</i> thermal bridging, infiltration
limits, control logic, shading geometry—but they cannot validate that a
proposed model follows the laws of thermodynamics or matches local climate
files, geometry, or construction systems.</p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>2. Regulatory interpretation and compliance judgement</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">“EE-04 weighted existing vs proposed floorspace” or “NCC
2019 Amdt.1 vs NCC 2022 equivalence under Building Surveyor discretion”
requires <i>professional reasoning</i>, not pattern-matching.</p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>3. Ethical accountability</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">A human must sign the report, take responsibility for
accuracy, and engage with BS, council, or GBCI when queries arise.<br>
LLMs cannot accept liability.</p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>4. Integration with design reality</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">Your point about tying design modelling to <i>actual
operation</i> (post-occupancy calibration) is spot on. This is something only
competent practitioners can deliver.</p>
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<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>How do we improve—and protect—the value of our work?</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>1. Strengthen the link between models and real buildings</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">Your proposal is exactly where the profession needs to move:</p>
<ul style="margin-top:0cm;margin-bottom:0cm" type="disc">
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">Require
calibration against measured operational data</li>
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">Use
design models to support commissioning and tuning</li>
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">Close
the loop between predicted and actual performance</li>
</ul>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">This pushes our value upstream and downstream—far beyond
simply generating documentation.</p>
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<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>2. Escrow the model input files</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">I strongly support this.</p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">For LEED, NatHERS, NCC performance solutions, mechanical
simulations, etc., requiring:</p>
<ul style="margin-top:0cm;margin-bottom:0cm" type="disc">
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">the
native model files,</li>
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">all
geometry and input assumptions,</li>
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">weather
files,</li>
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">software
versions,</li>
</ul>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>to be lodged with a trusted authority (GBCI, local
regulator, building surveyor, etc.)</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">would limit the risk of “paper-only” submissions.<br>
Reports must correspond to verifiable inputs.</p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">This is analogous to the way:</p>
<ul style="margin-top:0cm;margin-bottom:0cm" type="disc">
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">structural
engineers submit their calculation sets,</li>
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">energy
auditors submit calibration data,</li>
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">certifiers
maintain audit logs.</li>
</ul>
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<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>3. Accreditation that requires evidence of actual
modelling competence</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">This could be NatHERS, CIBSE, ASHRAE, or emerging Australian
equivalents.</p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">An LLM can write a report.<br>
It cannot apply ASHRAE 140, NCC V2.6.2.2, or interpret ambiguous DTS pathway
conflicts.</p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">A competency-based accreditation system reinforces the value
of the practitioner, not the document.</p>
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<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>4. Transparency in documentation</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">Professionals should adopt a standard such as:</p>
<ul style="margin-top:0cm;margin-bottom:0cm" type="disc">
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">Model
version</li>
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">Software
version</li>
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">Data
sources</li>
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">Assumptions</li>
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">Calibration
status</li>
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">QA/QC
logs</li>
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">Sensitivity
tests</li>
</ul>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">This is the kind of information an LLM <i>cannot fake
accurately</i>—without the real model behind it.</p>
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<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>Controversial? Maybe. Necessary? Yes.</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">Your proposals won’t just protect the profession; they will
improve the credibility of modelling outcomes and reduce the temptation for
individuals (or clients) to push for “report-only” shortcuts.</p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">The uncomfortable truth is:</p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>LLMs threaten the <i>commoditised paperwork</i> side of
our profession,<br>
but they strengthen the value of genuine expertise and verifiable modelling.</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">If we move towards transparent inputs, post-occupancy
calibration, and audited modelling files, then the future modeller becomes:</p>
<ul style="margin-top:0cm;margin-bottom:0cm" type="disc">
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">a
systems thinker,</li>
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">a
regulatory interpreter,</li>
<li class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">a
data integrator,</li>
</ul>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"> </p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">—not a “report generator.”</p>
<div class="MsoNormal" align="center" style="text-align:center;margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">
<hr size="2" width="100%" align="center">
</div>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><b>Thanks for raising this, Chris. This is exactly the kind
of conversation the industry needs to be having right now.</b></p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif">Cheers,<br>
Richard<br>
(Building Designer & Energy Efficiency Assessor)</p>
<p class="MsoNormal" style="margin:0cm 0cm 8pt;line-height:107%;font-size:11pt;font-family:Aptos,sans-serif"><span style="font-size:16pt;line-height:107%">eco<span style="color:rgb(0,176,80)">designs </span></span><span style="font-size:10pt;line-height:107%">know the elements, work with them</span><span style="font-family:Arial,Helvetica,sans-serif;font-size:small"></span></p></div><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div></div></div></div></div><br></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Thu, 11 Dec 2025 at 00:40, Chris Yates via Bldg-sim <<a href="mailto:bldg-sim@lists.onebuilding.org">bldg-sim@lists.onebuilding.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="msg6722942565527614276">
<div lang="EN-GB" style="overflow-wrap: break-word;"><div class="m_6722942565527614276WordSection1"><p class="MsoNormal">Hi there,<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">Just a philosophical one; maybe even an existential one <span style="font-family:"Segoe UI Emoji",sans-serif">😐</span><u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">Given LLMs’ “autocorrect on steroids” abilities, what risk do we see ourselves exposed to as modelling professionals?<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">Let’s give an example…<u></u><u></u></p><ul style="margin-top:0cm" type="disc"><li class="m_6722942565527614276MsoListParagraph" style="margin-left:0cm">A full LEED application including reports, unmet load tables, “error” reports. <u></u><u></u></li><li class="m_6722942565527614276MsoListParagraph" style="margin-left:0cm">Not based on modelling – all reports and outputs generated with LLMs.<u></u><u></u></li></ul><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">I think it would be relatively easy to do this, and present something that would stand up to review.<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">I think this poses the following questions:<u></u><u></u></p><ol style="margin-top:0cm" start="1" type="1"><li class="m_6722942565527614276MsoListParagraph" style="margin-left:0cm">If our main value offering can be replaced with auto-complete, what is the value of what we’re doing, anyway?<u></u><u></u></li><li class="m_6722942565527614276MsoListParagraph" style="margin-left:0cm">How can we improve the value?<u></u><u></u></li><li class="m_6722942565527614276MsoListParagraph" style="margin-left:0cm">How can we protect that value?<u></u><u></u></li></ol><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">I’d like to propose some solutions:<u></u><u></u></p><ul style="margin-top:0cm" type="disc"><li class="m_6722942565527614276MsoListParagraph" style="margin-left:0cm">Tie Design stage models into the Operation of the building – calibrate<u></u><u></u></li><li class="m_6722942565527614276MsoListParagraph" style="margin-left:0cm">Rather than just submitting reports, place model input files into <b>escrow</b> with GBCI (or their local equivalent)<u></u><u></u></li></ul><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">Controversial?<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">Cheers<u></u><u></u></p><p class="MsoNormal">Chris<u></u><u></u></p></div></div>_______________________________________________<br>
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