When condensation and mould end up in dispute — the modelling is the part you’re not worried about.
Mould and condensation disputes land on whoever signed the design off. AFRC Lab models the real interfaces in your project — windows, walls and the junctions between them — for condensation, mould and energy to ISO 15099, the international standard. Not a generic rating. The result is on the record before it’s built: if it’s modelled, that’s your evidence — if it isn’t, it’s “we didn’t know.”
AFRC Lab engine
Sill section · thermal + condensation
ISO 15099 · live
What do you need to prove?
Jump straight to it — or scroll on for the full picture.
Three ways to work with us.
From a self-serve number to a full forensic dossier — pick the depth the project needs.
BTW — Build The Window
Model the window you’re actually installing to ISO 15099 — one build returns the whole output set, and reverse-engineers the glass and frame to hit your target. The accurate alternative to WERS/DTS defaults.
- Uw, SHGC, Tvis & R — any size, config & glass
- Condensation / mould scan
- Embodied carbon, recyclability & weight
- Reverse-engineers glass & frame to a Uw / SHGC target
TIRS™ MI-6
The condensation compliance number. An Outcome X forensic assessment that returns the Mould Index (ISO 13788 / VTT) your project needs for NCC condensation — the sole determinant under F8V1 / H4V5.
- Decision-ready Mould Index vs the 3.0 limit
- Per-junction, per-climate-zone
- Audit-ready evidence for the certifier
TIRS™ — full suite
The complete forensic dossier: condensation and heat loads, full thermal performance and per-section working — the whole window, evidenced. The depth behind our case-study work.
- Everything in MI-6 — across Outcome X, winter & summer
- Heat loads & full thermal performance
- Solar & vapour analysis
- Per-section working (frame, sash, edge, COG) across the glass ladder
Scope and outputs are confirmed per project. BTW, TIRS™ MI-6 and the full TIRS™ suite all produce verification data; final NCC compliance is determined by your assessor / certifier.
This is what you actually get.
A redacted page from a live TIRS™ MI-6 assessment — the exact compliance gate a certifier sees. No black box: the number, the limit, and the forensic inputs behind it.
| NCC compliance gate | Result | NCC limit | Status |
|---|---|---|---|
Mould Index AIRAH DA07 (ISO 13788 / VTT) · sole NCC determinant | 2.59 / 6 | ≤ 3.0 | Within limit |
| Forensic metric | Outcome X | CZ target | Band |
|---|---|---|---|
| Min surface temp (Ti) | 13.62 °C | ≥ 12.6 | Acceptable |
| Temperature factor (fRsi) | 0.68 | ≥ 0.43 | Robust |
| Surface humidity (RHsi) | 75% RH | ≤ 80% | Marginal |
Sample output, client details redacted. Every MI-6 assessment returns this gate — per junction, per climate zone. Final NCC compliance is determined by your assessor / certifier.
We don’t just find the problem. We model the fix.
Most assessments stop at a red flag. We model the interface as it’s designed, show exactly where it fails — then re-simulate the build-up until it passes. You leave with a path to compliance, not just a problem. And it’s not only windows: any interface or junction where warm inside air meets a cold surface.
Model as designed
The real build-up — windows, walls and the junctions between them — modelled to ISO 15099.
Find where it fails
Surface temperature, condensation and the Mould Index, junction by junction — the exact spot the risk sits.
Re-simulate the fix
Change the build-up, re-run, and hand you the version that clears the NCC limit.
83% RH · above the mould line
75% RH · within limitModelled fields shown are indicative visualisations of a real assessment; project, client and system details redacted. Results are indicative to the systems and sizes provided; final NCC compliance is determined by your assessor / certifier.
The lab the consultants consult — and the builder’s compliance security blanket.
H/F condensation compliance on glazed façades is genuinely misunderstood — by the consultants as much as anyone. That’s why ESD and façade engineers already lean on our modelling, not just window manufacturers. AFRC Lab works at a rare intersection in this country: building physics, fenestration and façade systems, and the NCC — windows, walls and the interfaces between them, under one roof. The new offerings extend that same certainty to the builders carrying the compliance risk.
Two ways to prove it. BTW is the other one.
Separate question now: not what you must meet (Section J, and Section H/F), but how you prove it. The NCC is a performance-based code — a window complies by the prescriptive Deemed-to-Satisfy default (where WERS lives), or by a Performance Solution assessed against the Requirement directly. That second route is the other compliance path, and it’s the one BTW is built for.
The prescriptive default
The recipe route — default look-up values, with WERS defaults standing in for the glazing. Generic, and often over-specified.
- ·A generic standard size, not your opening.
- ·Conservative defaults that can inflate the spec — and the price.
- ·Silent on condensation and mould.
A verified outcome for your actual window
BTW models the window you’re installing — real size, configuration and glass — to ISO 15099, serving three of the four NCC Assessment Methods (NCC A2.2).
- →Evidence of Suitability — whole-window Uw, SHGC & Tvis, showing the window is fit for purpose.
- →Verification Method — feeds Section J / NatHERS energy verification.
- →Comparison with the Deemed-to-Satisfy Provisions — your real number against the default.
AFRC Lab provides the verification data; your certifier determines compliance. We give you the modelled evidence — you achieve the certification. The performance path is a valid, Code-recognised route to compliance; for windows, the WERS/DTS default is one option, not a requirement.
Section J is the box everyone ticks. Section H/F is the one that bites.
Here’s the uncomfortable truth: almost nobody fully understands Section H/F — ESD consultants, builders and architects included, and most of all on glazed façades. A window can pass the energy box and still grow mould in winter. No jargon — here’s what it actually is.
Energy
U-value and SHGC against the energy budget — the number the industry has optimised around for years. BTW supplies the whole-window Uw and SHGC that feed it (DTS elemental, NatHERS or JVx). Necessary and familiar — rarely the thing that goes wrong once the window’s in.
Uw · SHGC · TvisHealth & Amenity
Since NCC 2022 it’s a requirement, not a nice-to-have — Section F, Part F8 for Volume One apartments & commercial, or Section H, Part H4 for Volume Two houses, whichever applies (NCC Verification Methods F8V1 / H4V5). BTW screens the inside-frame surface temperature, zone by zone; the full forensic assessment is TIRS™, which scores the Mould Index (ISO 13788 / VTT) — the sole NCC determinant. Get the system or the sub-frame wrong and a window that passed on energy grows mould in winter.
fRsi · θsi,min · Mould Index ≤ 3.0The black box, opened.
No one expects you to already know this — most of the industry doesn’t. Here’s the whole thing, in plain English.
Section J covers energy. Section H/F (Health & Amenity) covers condensation and mould — keeping moisture off the inside of the building. Since NCC 2022 it’s mandatory: Part F8 in Volume One (apartments & commercial), Part H4 in Volume Two (houses). Miss it and the build isn’t compliant.
Frames and glass edges run colder than the rest of the wall. On a glazed façade there’s more cold surface, more thermal bridging at the junctions, and more chance warm indoor air meets a cold surface and condenses. It’s exactly where H/F bites hardest — and where it’s least understood.
When an indoor surface gets cold enough, moisture condenses and mould can grow. The risk is scored as a Mould Index (the AIRAH DA07 Mould Index — ISO 13788 / VTT basis) — a 0–6 scale, NCC limit 3.0 — and it’s the sole NCC determinant for condensation. Surface temperature, fRsi and surface humidity aren’t separate tests; they’re the forensic inputs that produce the index. Below 3.0, managed; above it, non-compliant — and a genuine health problem for the people inside.
ISO 15099 is the international standard for simulating heat flow through a window or façade section — and the whole local system already rests on it. The NCC calls up the AFRC rating protocols, which run on THERM and NFRC 100 — and NFRC 100 is built on ISO 15099. So it isn’t foreign; it’s the foundation under every Australian window number. (That council is the AFRC — we’re AFRC Lab, the independent lab working to the same basis.) It produces the U-values and the surface temperatures, at a worst-case “restricted convection” condition (ISO 13788’s Rsi 0.25), and those surface temperatures are what the Mould Index is calculated from.
A generic rating (like a WERS default) describes a standard product at a standard size — not your opening, your glass, your sub-frames. The window that actually gets installed can perform very differently. BTW models the real thing, so the compliance number reflects what’s on the building.
Plain-English summary. The Mould Index is the AIRAH DA07 Mould Index (ISO 13788 / VTT basis) and is the sole NCC determinant for condensation (NCC 2025 Verification Methods F8V1 / H4V5, retained from NCC 2022); surface temperatures come from ISO 15099 thermal simulation. Final NCC compliance is determined by your assessor / certifier.
Short list, meet long list.
WERS is a solid comparison-and-labelling scheme — built to line products up on a common basis, and good at it. But your project isn’t a line-up; it’s a specific window in a specific opening. Different job — and the one BTW is built for.
WERS — what you get
- ·A generic standard size — not your window.
- ·One generic configuration, one specimen.
- ·A single fixed result and a star label.
- ·Cryptic generic naming codes to decode.
- ·A headline number — the working stays on the server.
BTW — what you get
- →Dynamic, project-specific modelling — your size & configuration.
- →Any glass make-up, per lite; your supplier’s own system names.
- →Whole-window Uw, SHGC, Tvis, R + per-section data.
- →Value-engineering to a target — glass & frame upgrades to hit it.
- →A condensation (fRsi) & embodied-carbon screen, plus a validated recyclability result.
- →Thermal images and per-section working — the science on the page.
What ISO 15099 is (few realise this): the international standard for simulating heat flow through a window or façade section — the method that sits behind both WERS and NFRC. Fair play: both WERS and BTW use it. The difference isn’t the physics — it’s what gets modelled: a generic standard-size specimen and a label, versus your actual window as project-specific verification data.
One tool, more answers.
Build the window once and it returns everything below — for any size, configuration and glass.
How to read these: Uw, SHGC, Tvis, R, recyclability and weight are validated results. Condensation (fRsi) and embodied carbon are screens — indicative flags, not the final word; where the condensation screen shows risk, the full forensic condensation & mould assessment is TIRS™. Condensation sits in NCC F8 / H4; carbon and recyclability are Green Star / NABERS territory — increasingly required, not extras.
Our CFL solver, checked against THERM 7.8.
Compliance is only as good as the engine behind it. Our in-house CFL solver (2-D ISO 15099) is validated head-to-head against LBNL THERM 7.8 — the reference the whole NCC chain rests on — section by section, at NFRC 100 conditions. These are real results, not a claim.
—
One method. Every market.
Building physics doesn’t change at a border — and neither does the method. Our engine is built on the international standards the whole industry already rests on, so the same model serves projects anywhere. Based in Australia; the new solver and THERM output open the door to many more markets.
The international backbone
- ISO 15099 — window & façade thermal simulation (global)
- ISO 13788 — condensation & surface humidity
- NFRC 100 + THERM — the North-American reference
Local codes sit on top of these. Get the physics right once, and it travels.
Output for your code
- Australia — NCC 2025 (Section J, H/F), via the AFRC chain
- North America — THERM / NFRC 100 files & U-factors
- Europe & Asia — ISO 15099 / ISO 13788 results, mapped to local code
The CFL solver and THERM output mean one model, many markets.
You set the targets. BTW solves the glass to hit them.
The default route is search a database, filter, and match a product that fits — one that then gets swapped on site. BTW runs the other way.
Pick the performance
Set the Uw and SHGC the project needs — the brief, not a catalogue.
Build the window
Size, splits and system straight off the drawings, for any opening type.
Solve the glass
BTW selects the glazing — and the frame if needed — to hit target. Glass is solved, not fiddled with.
Prove it
Modelled to ISO 15099 and exported as instant, audit-ready evidence.
Every NCC angle on a glazed façade.
Not just energy and condensation — the full set of performance data for glazed façades and fenestration. Where testing or certification is required, we deliver it through our accredited partners. We provide the verification data; you achieve the certification. Clauses shown are Australia’s NCC 2025 — the same ISO 15099 / THERM / NFRC 100 outputs map to codes in other markets.
Energy
Project-specific whole-window U-value & SHGC via BTW — ISO 15099 / NFRC 100, not a DTS default. Often a better, less over-specified result.
Condensation & mould
TIRS™ forensic hygrothermal analysis — the AIRAH DA07 Mould Index for health, amenity & moisture management.
Acoustic
Noise-attenuation metrics for glazed products — the Rw, C and Ctr data to hit sound-insulation thresholds.
Fire
Accredited partnersFire compliance of glazed façades, windows & doors — from system testing through fire-engineered Performance Solutions to certification. One point of contact.
Embodied carbon
Verification partnerUpfront-carbon data for façade & glazing — from BTW screening estimates to verified Product Carbon Footprints. Measure, reduce, disclose.
OPTISEALED™
Installation guidelines, structural connection details & weatherproofing strategies — so site practice is certifiable, not guesswork.
From our core out to the whole chain.
Window manufacturers are our core. The new offerings reach the consultants who want a specialist to lean on, and the builders who need someone accountable behind the numbers.
Our core. The real number so you quote sharp and win the work — your own systems, your branding, un-blurred reports.
The consultant’s consultant. Back your spec with the actual installed window so it survives shop-drawing stage — and hand us the fenestration physics you’d rather not own.
Your compliance security blanket. Prove the envelope before it’s locked, kill late-stage VE churn, and have someone accountable standing behind the window numbers.
Specify glazing you can trust is both buildable and accurate — genuinely fit for purpose on energy, condensation and mould.
Check the specified values reflect the window that’s actually installed.
The quiet one: a window that passes energy and still keeps the mould out in winter.
Log in — or hand it to us.
BTW clients log in and run their own projects on demand. TIRS assessments we deliver for you — send us the section and we’ll model it. New to BTW? Request access and we’ll set you up.
Build The Window
Model the window you’re installing to ISO 15099 — Uw, SHGC, Tvis, a condensation & mould scan, carbon and weight, reverse-engineered to your target.
Log in to BTW → TIRS™ · assessed by usThermal Interface Rating System
The forensic condensation & Mould Index assessment behind the compliance number — any interface, any junction, scored against the NCC limit. We run it; you get the report.
Request an assessment →Accounts are set up per fabricator / practice. Request access →
Thermal fields, before & afters, and the odd black-art explainer.
Channels are launching shortly — real modelled results, compliance notes, and what we’re seeing across Australian projects. The science, in public.