Frequently asked questions

How do I know the calculations are correct?

Thermly's engine is validated against authoritative references, not just its own tests:

• The whole-building heat-loss calculation is checked against the official BRANZ H1/AS1 6th edition Calculation Method spreadsheet. The reference coefficients, minimum R-values, the 70/30 wall split, the glazing cap and the skylight-in-roof treatment all match, and the proposed heat-loss figure reproduces the spreadsheet across a large test set.
• The construction R-values are regression-anchored to the NZS 4214:2006 worked examples: F1, F2 and F3 (steel) reproduce the standard's published results, and the F4 vented-cavity wall is pinned at the value the normative §5.3.2 rule gives, deliberately below the informative example's figure (see Air cavities).
• The method has also been reproduced against council-approved reports prepared with other tools.
• Every product R-value is sourced and shown with its provenance (see Product sourcing and provenance).

None of this removes your review. Thermly computes to the method faithfully; you confirm the inputs (areas, assemblies, product R-values) are right for the building. See How Thermly calculates compliance.

Who is responsible for a submitted report?

Sources and verification

This answer describes the professional-tool relationship - what Thermly does and does not do. It is the accurate description of the product, not a disclaimer bolted on.

You are, as the submitting professional, exactly as with any professional tool.

Think of how accounting software works: it does the bookkeeping arithmetic and produces the statements, and the accountant reviews and certifies the accounts. Thermly does the H1 thermal calculation and produces your consent-ready report; you, the submitting professional, review it and certify the compliance of what you submit.

Thermly computes construction R-values, runs the heat-loss comparison, and flags values that look unusual so you can check them. It does not certify, guarantee, warrant, or approve a compliant outcome, and it does not replace your professional judgement. That division is deliberate, and it is how the tool is built: Thermly computes and documents; the professional reviews and certifies. The report's own declaration says as much - it "does not constitute a certificate of compliance, council approval, or producer statement" - and it carries the name of the preparer and reviewer who stand behind it.

Can I use the report for consent submission?

Yes; that is what it is for. Thermly produces a complete H1/AS1 6th edition Calculation Method report: the heat-loss result, the per-element construction schedule and build-ups, the compliance checks, the required disclosures, your marked-up plan diagrams, and a declaration block.

Two things to be clear about:

• The report is the calculation and documentation, presented for a named professional to certify. It is not a compliance certificate, a producer statement, or council approval in itself, and it says so on the declaration. The building consent authority makes the compliance determination.
• Complete the declaration - the preparer and the reviewer. The report is strongest when a suitably qualified professional has reviewed it and put their name to it.

Used that way (your calculation, your review, your name) the report is built to go straight into a consent application.

Should I work from a plan or enter areas?

Either, and you can choose per element. Working from the plan gives you a measured take-off, a marked-up diagram in the report, an insulation take-off, and a plan-linked project. Entering areas directly is faster when you already have trustworthy numbers. The compliance calculation is identical either way. See Working from a plan or entering areas.

Which standards does Thermly implement?

Two:

• NZS 4214:2006 for construction R-values (the isothermal-planes method, surface resistances, cavities).
• H1/AS1 6th edition Calculation Method for the whole-building heat-loss comparison against the reference building, and Appendix E for slab-on-ground and raft floors (the slab lookup).

Both are licensed standards; Thermly implements their methods so you do not have to work from the documents, though you remain the professional who certifies the result. See How Thermly calculates compliance.

What happened to the Schedule Method?

It was removed in H1/AS1 6th edition. From 27 November 2026 the Schedule Method can no longer be used; residential H1 compliance uses the Calculation Method (which Thermly implements) or the Modelling Method. The 5th edition and its schedule remain valid for consents submitted before that date. See The 27 November 2026 change.

Where do the product R-values come from?

From primary sources - manufacturer datasheets first, then the NZS 4214 reference tables - shown with their provenance via Show source on each product. Thermly does not use competitor calculators as a source. Many datasheet values are AI-extracted and should be checked against the current datasheet before use. See Product sourcing and provenance.

How do I enter a raft or proprietary floor?

A proprietary raft's R-value depends on your floor's geometry, so the manufacturer determines it per project. Run the manufacturer's calculator for your floor and enter the supplied R-value with its source document; you confirm the calculator determines the value in accordance with H1/VM1 Appendix E, and Thermly records the basis (Appendix E, Paragraph E.1.1.1(b)), your confirmation and the source - all stated on the report, with the calculator's full URL. A plain slab uses the slab wizard instead. See Supplied floors and rafts.

What are the sample projects on my Dashboard?

Every account gets read-only demonstration projects, listed ahead of its own and marked "Sample". The first is "123 Sample Street, Sampletown", and there may be others. Each is complete: a plan, a finished take-off, assemblies and pre-computed AI results (the plan summary and an AI Review), so you can see a finished job before starting your own. View sample to explore one; Copy to edit (or Make a copy from inside it) duplicates everything into a fully editable project of your own. A report generated from a sample is marked "Sample" on its cover and never spends a report credit. The samples are centrally managed, so they may update over time - your copies never change.

What does Thermly cost?

Thermly is currently in free open-access testing: nothing is charged, and free access never turns into a charge without your agreement. The Pricing page sets out how it will work once payments are switched on, and it is the place to look for current prices. The durable points are these:

• Building is free. Creating and editing projects, the Assembly Builder and the product catalogue, plan mark-up and take-off, AI plan reading within a fair-use allowance, sharing within an organisation, and watermarked preview reports never cost anything.
• A report credit is spent once per project, when you generate that project's first consent-ready report (one without the preview watermark). Thermly asks before it spends one. Every later report for that project, however many revisions, is free. There is no subscription, and credits do not expire.
• The insulation take-off is always free, and so is any report from a sample project.
• Every account starts with one credit, and your balance shows in the header once payments are on.

A credited or finalised report is for one building. Revising it for that building is always fine; reusing it for a different one is not what a credit covers.

Can I use Thermly for an alteration or addition?

Yes. Set the project's Building work to Alteration or addition and mark each element as new building work, existing and unchanged, or existing and altered. Thermly compares only the new work with the reference building, leaves untouched existing fabric out of the calculation altogether (no R-value is claimed for it), and checks that the fabric you alter performs no worse than it did before. The report sets all of that out in a section of its own. See Alterations and additions, and for the rules behind it the public guide H1 for alterations and additions.

Is there a free calculator I can try without an account?

Yes: the free H1 calculator. Pick your council to set the climate zone, describe the roof, walls, floor, glazing, doors and skylights from a short list of generic constructions (or type an R-value), and the same engine returns an indicative whole-building PASS or FAIL. It is for early design decisions. Its PDF is marked as indicative and is not suitable for a consent application; for that you need a project, which is what the rest of this guide covers.

What does AI Review check?

AI Review (in the report bar, beside AI Summary) is a one-click pre-flight over your current inputs: gaps such as a missing climate zone or envelope element, compliance blockers such as a failed minimum or the glazing cap, and risks such as thin headroom or sub-38% framing without a recorded demonstration. The deterministic checks are free and read the same warnings the H1 page shows you. With a plan attached they include each opening's size against the size the drawings state, and whether every floor plan of a multi-storey set was traced. An AI pass also cross-checks your entries against the uploaded plan - the insulation spec vs your chosen build-ups, the window schedule vs your openings, elements the plan shows but the project lacks - with every AI-raised finding tagged as AI, held to the same fixed rulebook, and accompanied by a note that AI can make mistakes. The review is advisory only: it never issues a compliance verdict and nothing from it prints on the report. It saves with the project and only regenerates when your inputs change. See AI Review: the pre-flight check.

Can I share projects with my team?

Yes. Create or join an organisation, then use shared folders that everyone on the team can see. Invite members by email with an Admin or Member role. Colleagues can add comments against each element at any status - a submitted project stays reviewable - and the In Review status marks a project as set aside for that final check. See Setting up a project.

Is my data private?

Your projects and plans are stored against your account and are visible to you (and, for shared projects, your organisation). Plan PDFs upload to secure storage and are available to view and download whenever you reopen a project. The plan-reading AI features (Read with AI, the AI plan summary, the AI pass of AI Review) are on for every account by default and process the plan with AWS-hosted models under your account - see the privacy policy for where application data may be processed. An administrator can switch AI off for an account, and the features then stay disabled with a tooltip saying so.

Why is an AI button disabled?

Its tooltip gives the reason, and there are three. AI features may have been switched off for your account, in which case an administrator can switch them back on. Your monthly allowance of AI plan reads may be used up; it resets at the start of the next month. Or today's AI allowance may be used up; it resets at midnight UTC. None of this affects the calculation, the report, or the free deterministic checks in AI Review.

How do I report a problem or suggest a feature?

Use the Feedback link in the header (on a narrower window it is inside the menu at the top right). It opens Thermly's feedback form: pick Bug, Suggestion, Question or Other, write your note, and optionally attach a screenshot. Every submission automatically includes your account email as the reply-to, the page you came from, your browser, and the exact app version - so a bug report arrives with the context needed to reproduce it.

Not signed in? The public contact form reaches the same inbox - name, email, a topic and your message.