About Thermly

What Thermly does

Thermly helps calculate and document thermal performance for New Zealand building consent work.

It supports two related workflows:

Thermly is designed to make H1 documentation faster, clearer, and easier to audit, with traceable product data, saved assemblies, and report-ready outputs.

Calculation method

For simple, continuous layers, Thermly uses the product's published or entered R-value.

For bridged layers, such as insulation between timber framing, Thermly applies the parallel-path method:

R_layer = 1 / (f_framing / R_framing + f_insulation / R_insulation)

The total construction R-value is then calculated as:

R_total = Rsi + Σ R_layers + Rso

Surface resistances are based on NZS 4214:2006 Table 1:

Values are expressed in m²K/W.

Thermal bridging and framing fraction

For framed wall construction, H1/AS1 6th edition requires a framing fraction of no less than 38% to be assumed unless the designer can justify a lower value using an accurate framing layout calculation.

Thermly defaults wall bridged layers to 38% framing. It also includes a framing layout calculator so users can estimate an alternative framing fraction from member spacing, member width, and nogging layout where appropriate.

H1/AS1 compliance workflow

Thermly includes an early-access whole-building H1/AS1 compliance workflow for housing and other buildings within the scope of H1/AS1 6th edition.

The workflow allows users to enter the relevant thermal envelope elements, including:

• roof areas;
• wall areas;
• slab-on-ground floors;
• other floors;
• wall glazing;
• opaque doors;
• skylights.

Each element can have its own area and construction R-value. Where appropriate, Thermly can use saved assemblies, default H1/AS1 values, or table-based lookups for generic glazing and slab inputs.

The result is a whole-building heat-loss check and a draft H1 compliance report intended to support review and testing during early access.

H1 compliance report

Thermly can generate a printable H1/AS1 compliance report PDF from the building envelope inputs.

The report is intended to help test and refine the documentation workflow. It may include project details, building information, climate zone, envelope inputs, R-values, calculation results, and supporting notes.

At this stage, generated reports should be treated as draft outputs only. They should not be submitted for building consent or relied on for commercial design work.

Product data

Thermly's product records are built from published manufacturer information wherever available.

Product R-values are either:

• taken from manufacturer datasheets;
• calculated from published thermal conductivity and thickness values; or
• derived from recognised standard material values where product-specific data is not available.

Each product record includes source metadata so the value can be traced back to the document or dataset it came from.

Product data is collected and maintained using an AI-assisted extraction pipeline. This allows Thermly to process a broad catalogue of manufacturer data, but it does not remove the need for verification. Manufacturers can update products, datasheets can change, and extraction errors are possible.

Before relying on any product value, users should verify it against the manufacturer's current published data.

Standards and references