How the calculations work, what standards they reference, and where they apply.
R-value calculations use the combined averaging method from NZS 4214:2006, the normative method cited in H1/AS1. The total resistance of a framed element is the arithmetic mean of the isothermal planes bound and the parallel path bound — capturing the physically limiting cases of lateral heat redistribution through thermal bridges.
Surface resistances follow NZS 4214 Table 1. Vented cavities apply the standard 0.5× reduction to layers exterior of the cavity per H1/AS1.
The dewpoint visualiser uses the Glaser method (ISO 13788:2012) to screen for interstitial condensation. Temperature varies linearly with thermal resistance; vapour pressure varies linearly with equivalent air layer thickness (Sd = μ × d). A condensation risk plane exists wherever actual vapour pressure meets or exceeds saturation pressure.
This is a steady-state screening tool. It does not account for capillary transfer, air leakage, or hygroscopic buffering. Where the screen flags a risk, BRANZ SR344 provides calibration: humidity at the sheathing reached 100% in almost all tested walls, but liquid condensation only formed in a minority. Standard NZ assemblies with acrylic paint and drained cavities perform adequately in temperate zones without dedicated vapour control layers.
Span tables, member sizing, and bracing demand tools implement the lookup procedures from NZS 3604:2011 — Timber-framed Buildings. Inputs are indexed by loaded dimension (tributary width), timber grade, spacing, and load category. Roof weight is classified as light (≤ 20 kg/m²) or heavy (> 20 kg/m²). Floor imposed load is 1.5 kPa residential per AS/NZS 1170.1.
Wind pressure uses AS/NZS 1170.2:2021 with terrain categories TC1–TC4, topographic multipliers, and NZ wind regions A1–A7/W.
Hazard class lookup for timber elements from H1.2 (interior framing) through H5 (aggressive ground contact), determined by exposure conditions per NZS 3602:2003. Common errors include using H1.2 where H3.1 is required — for example, bottom plates within 150 mm of ground.
All outputs are for preliminary design and educational purposes. They do not replace formal building code compliance documentation. Results must be verified by a qualified professional against specific project conditions and the current NZBC amendment at time of consent. For complex assemblies, transient hygrothermal simulation (WUFI) is recommended.