Hygrothermal analysis models how heat and moisture move through a wall or roof over time, using local weather data. It shows whether condensation will build up inside the assembly and whether mould could grow there. NCC 2025 Part F8 sets the condensation rules, and the ABCB Condensation in buildings handbook explains how to meet them.
Send us your wall assembly and project location. We'll confirm scope and turnaround.
Condensation risk often isn't about how much insulation a wall has, but where it sits, and where the vapour control layer sits relative to it. Moisture can build up season by season, out of sight, if the wall can't dry fast enough. Modelling at design stage tells you how your wall will behave before it's built, and gives you a documented basis for the decision.
A wall that performs well in a warm, humid climate (NCC climate zone 2) may behave differently in Melbourne (climate zone 6). We model your assembly with hourly climate data for your project location, rather than relying on a rule of thumb.
The NCC's Deemed-to-Satisfy condensation provisions set general rules for membranes, cavities and ventilation. They don't test your specific assembly in your climate and occupancy. Modelling does, and for apartments and houses it can also support a Performance Solution, using Verification Method F8V1 (Volume One) or H4V5 (Volume Two).
Moving a vapour control layer, switching insulation type, or adding a ventilated cavity gap. These are specification-stage decisions. Hygrothermal modelling tests these options and indicates which may reduce risk before construction.
Hygrothermal modelling simulates heat and moisture movement through walls, roofs or floors over time, under the climate and indoor conditions of your project. We use WUFI Pro, software developed by Fraunhofer IBP that meets the EN 15026 standard for transient heat and moisture simulation, to assess where moisture may accumulate, condensation risk at critical interfaces and seasonal drying potential.
For apartments (Class 2 sole-occupancy units), Class 4 parts of buildings and houses (Class 1), modelling can also support a Performance Solution. Verification Methods F8V1 (Volume One) and H4V5 (Volume Two) accept a roof or external wall assembly where modelling to AIRAH DA07 shows a mould index no greater than 3 on the interior surface of the water control layer, or on the materials inside it. NCC Part F8 applies only to Class 2 sole-occupancy units and Class 4 parts of buildings. For pools, offices, schools, aged care and other commercial buildings, modelling is best practice and risk management rather than NCC compliance.
NCC 2025, adopted in Victoria from 1 May 2026, strengthens the condensation provisions for walls and roofs in Volume One Part F8 and Housing Provisions Part 10.8, including Deemed-to-Satisfy requirements for drained and ventilated wall cavities in climate zones 6, 7 and 8, which covers Melbourne. These apply to Class 2 sole-occupancy units, Class 4 parts and houses, with some exceptions. Where a design departs from those provisions, modelling under F8V1 or H4V5 is one way to show compliance. The best time to engage is design development, while assembly decisions are still open.
Interstitial condensation assessment estimating whether moisture may form within the assembly and when risk is highest. Identifies critical interfaces and evaluates severity under the selected climate and boundary conditions.
Mould risk at critical material interfaces, assessed with the VTT mould index (the method used by AIRAH DA07 and NCC F8V1/H4V5, with a limit of 3) or Fraunhofer's WUFI-Bio model, depending on what the project needs. Where risk exceeds the adopted criterion, we assess practical modifications such as vapour control layer position, insulation type or cavity ventilation.
A hygrothermal report from Makao goes beyond a pass–fail result. It identifies where and when moisture risk is highest and which modifications may reduce it. Where results exceed adopted criteria, we model a revised option and include comparative outputs in the same report, within reason; significant variations, incomplete information, major design changes or extra scope are clarified upfront.
Temperature and relative humidity plots at selected material interfaces across the simulation period. Indicates where and when moisture accumulation risk is highest.
Identification of the critical interface where interstitial condensation risk is highest, with quantification of severity under your local climate. Includes drying potential assessment across seasons.
Mould risk at critical material interfaces using the VTT mould index (AIRAH DA07, NCC F8V1/H4V5) or WUFI-Bio, as the project requires. Where the result exceeds the adopted criterion, we model a revised assembly to compare residual risk.
Where results exceed adopted criteria, we recommend practical modifications — vapour control layer repositioning, insulation changes, or cavity addition — and compare revised model outputs with the baseline.
You need hygrothermal modelling when a wall, roof or floor assembly carries moisture risk that standard design checks won’t show. Common triggers are a system proven in a different climate zone, builder defect risk, mould investigations and high-humidity buildings such as pools, gyms and commercial kitchens. These are the situations where that risk is most often hidden.
Climate mismatch — a system proven in a warmer climate zone hasn't necessarily been tested in Melbourne (climate zone 6), where cool winters and indoor moisture from cooking, showers and airtight construction drive vapour outward into the wall. We model the specific assembly in your climate before it's built, so you can specify it with confidence.
Defect risk — condensation and mould problems can appear years after handover, when they are costly to fix and hard to defend. A documented hygrothermal assessment at design stage shows the assembly was tested for its climate and occupancy, and gives the builder and developer a clear record of the decision.
Mould investigation — without visible water ingress, possible causes include surface or interstitial condensation, thermal bridging, ventilation or a concealed moisture source. We model representative conditions to test the likely mechanisms, giving the owners corporation, builder and their advisers a clear technical basis for remediation.
High-humidity buildings — pools, gyms and commercial kitchens, and sometimes densely occupied schools or aged care, carry indoor moisture loads well above standard assumptions. The NCC's condensation provisions don't cover these building classes, so modelling is best-practice risk management: it shows how the envelope will cope before it's built.
Product validation — manufacturers and suppliers use hygrothermal modelling to show how their system performs in Australian climates and typical wall or roof build-ups, including mass timber, CLT and prefabricated panels. We document material data, assumptions and results so your technical team and customers can review them.
Vapour control layer disputes — layer position can materially influence envelope moisture behaviour. We model both configurations under the project climate and occupancy conditions, then compare relative risk and document the assumptions, findings, and limitations.
Late-stage assembly changes — orientation affects driving rain exposure, solar radiation and drying potential, and performance can vary between façades. For urgent projects, we can fast-track modelling of the changed assembly and assess the modified specification against stated risk criteria.
Insurer or warranty request — insurers, warranty providers and professional indemnity reviewers may ask for evidence on prefabricated, off-site or non-standard systems. We provide structured WUFI reports with material references, findings, assumptions and limitations for their review.
Wall assembly specification, project location, occupancy type, and any certifier or insurer correspondence. We’ll confirm scope, turnaround, and whether modelling is warranted within one business day.
Assembly layers, material properties and vapour control positions reviewed, and climate and indoor conditions set for the project. Higher-risk assemblies are flagged before modelling begins.
Transient coupled heat and moisture simulations across multiple years of climate data. Outputs include temperature and RH profiles at each layer, condensation events and the mould index at critical interfaces.
A clear report translating simulation outputs into design decisions. Where results exceed adopted criteria, we assess revised options and include comparative outputs. Formatted as NCC Performance Solution evidence (F8V1/H4V5) for your building surveyor, or for insurers, manufacturers or other stakeholders, where agreed.
Hygrothermal modelling simulates heat and moisture movement through an envelope assembly over time, under the climate and indoor conditions of your project. Using WUFI Pro, we assess potential moisture accumulation, condensation risk at critical interfaces and seasonal drying potential. It shows conditions inside the wall, not only at the surface.
The main triggers: highly insulated or airtight assemblies; cool or mixed climates such as Melbourne (NCC climate zone 6), Canberra and alpine sites; high-humidity buildings such as pools and commercial kitchens; mass timber, prefabricated or unconventional systems; insurer, warranty or certifier requests; and designs that depart from the NCC's condensation provisions. It is also used to investigate existing buildings with mould or condensation defects.
We use WUFI Pro, developed by Fraunhofer IBP. WUFI is software that meets the EN 15026 standard for transient heat and moisture simulation; it isn't a standard itself. Inputs and assessment criteria follow AIRAH DA07 (adapted from ASHRAE 160). For mould risk we use the VTT mould index or WUFI-Bio, depending on the project, and state material data, assumptions and limitations in the report.
Modelling can support a Performance Solution for Class 2 sole-occupancy units, Class 4 parts of buildings and houses, using Verification Method F8V1 (Volume One) or H4V5 (Volume Two). These Verification Methods accept a roof or external wall assembly where modelling to AIRAH DA07 shows a mould index no greater than 3 at the water control layer or the materials inside it. Under NCC 2025, adopted in Victoria from 1 May 2026, this is one way to show compliance where a design departs from the Deemed-to-Satisfy provisions. For commercial buildings, modelling is best practice rather than an NCC requirement.
Not always. A Passive House certifier may ask for hygrothermal evidence for higher-risk assemblies. We provide that modelling as input to your Passive House designer and certifier. We don't provide Passive House design or certification, and final acceptance rests with the certifier.
Simulated temperature and relative humidity profiles; interstitial condensation risk assessment; mould index at critical interfaces (VTT or WUFI-Bio); annual moisture accumulation and drying balance; and practical design recommendations. Where results exceed adopted criteria, we model revised options within the same scope, within reason; significant variations, incomplete information, major design changes or extra scope are clarified upfront.
Your proposed wall assembly specification (layer by layer), project location, occupancy type, and any certifier, insurer or council correspondence. PDF drawings are fine. We'll advise on scope and confirm whether modelling is warranted within one business day. Engaging at design development, while assembly decisions are open, gives the most options.
Timeframes are confirmed at quote, and fast-track is available for urgent projects. The timing depends on the number of assemblies and the climate and indoor conditions to be modelled.
We use WUFI Pro — a widely used transient hygrothermal tool — to evaluate seasonal heat and moisture behaviour beyond simplified steady-state methods.
Assessments reference the NCC edition that applies to your permit, including NCC 2025 in Victoria from 1 May 2026, and the F8V1/H4V5 Verification Methods where relevant.
Reports set out method, inputs, assumptions, findings and limitations, so insurers, warranty providers and product manufacturers can review the basis of the result.
We engage during design development, while assembly decisions remain open. We model a revised option within the same scope, within reason; significant variations, incomplete information, major design changes or extra scope are clarified upfront.
A documented basis for envelope decisions, useful for building surveyors, defect-risk management and handover records.
Local knowledge of Victorian regulation, common assembly systems and climate-specific risks, working with projects across Australia.
Reviewed by Kelvin Mureithi, Founder, Makao · Green Star Accredited Professional, ISAP, Engineers Australia member.
