Common questions about building science

A blower door test measures how airtight a building is by installing a calibrated fan in an exterior door and pressurising and depressurising the building to 50 Pascals. The airflow required to maintain that pressure differential is measured and used to calculate the air leakage rate — expressed as air changes per hour at 50 Pa (ACH@50) for residential buildings, or air permeability q50 in m³/(h·m²) for commercial. The test identifies how leaky the building is, and where the leakage is occurring. See our airtightness testing service for full scope and coverage.

The most valuable test is a pre-line shakedown test — carried out before linings, ceilings, or cladding are installed, while leakage paths are still accessible. A failure at this stage is cheap to fix. A failure at practical completion means cutting out finished work. The final test confirms the result for certification or handover. For projects without a specific target, a single final test is standard.

Passive House Classic requires ≤ 0.6 ACH@50 Pa, tested to ISO 9972 Method 1 with all intentional openings sealed. PHI Low Energy Building and EnerPHit allow ≤ 1.0 ACH@50. The test must be carried out by a qualified tester — ATTMA accreditation satisfies the PHI requirement. Results are formatted for direct entry into PHPP.

Yes. Green Star Buildings requires ATTMA Level 2 accreditation and ATTMA TSL2 methodology — not standard residential blower door testing. The test must be accompanied by a formal Method Statement and submission-ready documentation including area-weighted results where sectional testing is required. See our Green Star ATTMA L2 service for full scope.

The building should be at or near practical completion — all exterior doors, windows, and penetrations installed and sealed, interior doors open, mechanical ventilation switched off. All intentional openings (ventilation terminals, trickle vents, exhaust points) will be temporarily sealed for Method 1 testing. We issue a pre-test checklist in advance so the site team knows exactly what's needed on the day. Incomplete preparation is the most common cause of a wasted test day.

H1 has three pathways. The Schedule Method checks R-values against a table — it's being withdrawn in November 2026. The Calculation Method allows limited envelope trade-offs and is available as a free tool — it's entry level but appropriate for straightforward projects. The Verification Method is full energy modelling (H1/VM1) — the most rigorous pathway, required for Passive House and high-performance projects, and the only one that produces verified energy demand data. See our H1 compliance page for a full comparison.

The Schedule Method is being withdrawn in November 2026. For most standard residential projects, the Calculation Method is the replacement — and it's free. Use our H1 Calculation Method tool for straightforward projects. For complex, non-standard, or high-performance projects, the Verification Method (H1/VM1) is the appropriate pathway. If you're unsure which applies, book a consultation.

Both model whole-building energy balance, but they use different tools and criteria. H1/VM1 demonstrates compliance with the NZ Building Code energy efficiency clause. PHPP (Passive House Planning Package) models the building to PHI certification criteria — heating demand ≤ 15 kWh/m²a, airtightness ≤ 0.6 ACH@50, and primary energy demand depending on the certification tier. A Passive House project will satisfy H1/VM1 as a natural output of PHPP modelling — we can run both from the same model to avoid duplicating work. See our energy modelling service.

Yes — that's what our Code-Ready compliance package covers. H1/VM1 energy modelling, E3 hygrothermal analysis using WUFI, and G4/G5 ventilation and thermal comfort assessment — all in one commission with consistent inputs and consent-ready reports. It avoids the inconsistencies that arise when compliance work is split across different consultants using different assumptions.

Condensation occurs when warm, moisture-laden air contacts a surface cold enough to drop below the dew point — causing water vapour to convert to liquid. Surface condensation is visible; interstitial condensation accumulates within the building assembly and is only detectable through analysis or when damage becomes visible. We assess condensation risk using WUFI Pro for dynamic hygrothermal analysis, the Glaser steady-state method (ISO 13788) as a first-pass check, and the surface temperature factor (fRsi) derived from thermal bridge FEA. See our condensation and WUFI service.

The Glaser method is a steady-state check — it treats moisture as a static problem and doesn't account for seasonal drying, material moisture storage, or the dynamic behaviour of hygroscopic materials. WUFI simulates heat and moisture transfer hour-by-hour across a full annual weather cycle, using real climate data. In NZ's mixed coastal and alpine conditions, Glaser consistently underperforms — it misses drying potential and can either overstate or understate risk depending on the assembly. WUFI gives a result you can act on. Glaser gives a result you can pass.

Not as a mandatory requirement for most projects. However, it is the appropriate method for demonstrating compliance under E3 Internal Moisture where Acceptable Solution methods don't cover the assembly, and under B2 Durability where standard solutions fall short. It also supports Performance Solution pathways under NCC 2022 for Australian projects. See our condensation service for the full compliance context.

A thermal bridge is any area of the building envelope where heat flows more easily than through the surrounding assembly — typically at junctions, structural elements, or where high-conductivity materials interrupt the insulation layer. Linear bridges (at junctions) are quantified as psi-values (Ψ, W/m·K). Point bridges (discrete elements like fixings) as chi-values (χ, W/K). Thermal bridges affect energy demand, create cold interior surfaces that can sustain mould growth, and in NZ/AU conditions, calculated psi-values can be worse than PHPP catalogue defaults — which means a project that looks compliant on paper may not be. See our thermal bridge analysis service.

In NZ and Australian conditions, catalogue values can underestimate heat loss — calculated psi-values can come in higher than the catalogue default, particularly at slab junctions and where NZ/AU construction typologies differ from European norms. This means a project using catalogue defaults may look compliant in PHPP when it isn't. The direction of error isn't predictable without modelling — which is precisely why calculating matters, especially for projects near the certification threshold.

fRsi is the surface temperature factor — it describes the minimum interior surface temperature at a junction as a ratio of the inside-to-outside temperature difference. A low fRsi means a cold interior surface. Where fRsi drops below the threshold for design conditions (typically 0.75 in NZ), the surface is cold enough to sustain condensation and mould growth. It's calculated from the same FEA model as the psi-value — an additional output, not a separate analysis.

Passive House is a performance-based building standard developed by the Passive House Institute (PHI) in Germany. The core criteria for Passive House Classic are: heating demand ≤ 15 kWh/m²a, cooling demand ≤ 15 kWh/m²a (or peak load ≤ 10 W/m²), primary energy demand ≤ 60 kWh/m²a, and airtightness ≤ 0.6 ACH@50 Pa. Plus and Premium tiers require renewable energy generation on top of the demand criteria. EnerPHit applies relaxed criteria for retrofit projects. All are modelled in PHPP and verified by a PHI accredited certifier.

Design consultancy covers the PHPP modelling, envelope advice, thermal bridge analysis, MVHR coordination, and documentation support that prepares a project for certification. Certification is the independent quality assurance review carried out by a PHI accredited certifier — resulting in the PHI certificate. They're separate services. BEO offers both. See our Passive House design service and certification service for the respective scopes.

Yes — through the EnerPHit pathway, which applies relaxed criteria to acknowledge that full thermal envelope continuity is rarely achievable in refurbishment. Two compliance routes are available: a component-based pathway (each element meets a specified standard) and an energy demand pathway (heating demand ≤ 25 kWh/m²a, climate-adjusted). Feasibility depends on the existing building — construction type, existing insulation, window replacement options, and services. An early feasibility assessment is the right starting point.

No. Certification is awarded on the basis of demonstrated compliance through verified documentation and independent quality testing — not on design intent. A project that meets the criteria in PHPP may still fail certification if the as-built condition deviates from the design, if the airtightness target isn't achieved on test, or if MVHR commissioning documentation is incomplete. The four-stage certification process is designed to identify and resolve these issues before they become irreversible. See our Passive House certification service.

Room integrity testing measures the leakage characteristics of an enclosure protected by a gaseous fire suppression system — FM-200, Novec 1230, CO2, or inert gas blends — and calculates the predicted agent retention time. The test confirms that the suppressant will remain at effective concentration for the required duration (typically ten minutes at the protected height). It's required at system commissioning and periodically thereafter. Typical applications: data centres, server rooms, archives, laboratories, plant rooms, and telecom switch rooms. See our room integrity testing service.

The equipment and principle are similar — both use a calibrated fan to pressurise an enclosure and measure leakage. The purpose and metric are different. Building airtightness testing measures ACH@50 for energy performance. Room integrity testing measures equivalent leakage area and calculates agent retention time for fire suppression compliance. Different standards apply: ISO 9972 for airtightness, ISO 14520 for room integrity. We carry out both.