Troubleshooting

My areas look wrong

Almost always a scale problem. Open the plan and check the scale chip: if it is amber ("Scale inherited from plan - re-calibrate for accurate areas"), the scale was carried over from another page. Re-calibrate against a known dimension on the page you are measuring. For a stretched or squashed PDF, use two-axis (H×V) calibration. See Uploading and calibrating your plan.

My traced walls show 0 m². The diagram has no scale at all, so the traced runs have no length to give the rows; the same happens to a roof or floor outline, which then has no area. A scanned plan with no text layer is the usual cause (Thermly cannot read the drawing's stated ratio from it), so the scale has to be set by hand. The diagram's card and each row linked to it say "Traced walls on this diagram have no scale, so no lengths reach the rows." with a Set the scale on the plan action: it reopens the diagram, where you click Scale, click two points on a known dimension and enter the real distance. Save the diagram and the runs you already traced become wall rows with their lengths, one row per colour. See Re-calibration is not optional for the calibrate step.

A roof area seems too small, or too large

Check the roof row's Pitch and its Ceiling follows pitch box, because together they decide which area counts. With the box off, the default, the heat-loss area is the flat plan (ceiling) area, which is right for a trussed roof with a flat ceiling: the insulation lies on the ceiling. With it on, the area is the larger sloped area, which is right for a skillion or cathedral ceiling that follows the rafters. The row spells out which it is using, and the plan label shows both figures, for example "45.50 m² ∠30° (plan 39.40 m²)". If a raked ceiling's roof reads small, tick the box; if a flat ceiling's roof reads large, untick it. See Roofs and ceilings.

An element shows no R-value, or the result is incomplete

Every element needs a complete assembly. A layer missing its product or R-value leaves the element's R undefined, and the row says so in a red notice that names each open slot, with Choose insulation… or Choose a product… to fix it on the spot. It is worth fixing first: an unfinished element is counted at the conservative §2.1.2.13 default of R0.18, which will usually fail the heat-loss check by itself. Assign a sample assembly to get moving, then complete the layers. See Assemblies and products.

The check fails, but I expected a pass

Look beside the verdict in the report bar. If it says one or more elements are at the §2.1.2.13 default, the failure may be nothing more than an unfinished construction: click the element named there to jump to the row, finish its build-up, and read the result again. An opening placed on the plan with no size yet has the opposite effect (it takes nothing out of its wall), which is why Thermly will not generate a report until every opening is sized.

I get a warning that my wall is below 38% framing

H1/AS1 6th edition assumes at least 38% wall framing (timber or steel) unless a lower fraction is demonstrated for the building. Use the H1/AS1 min (38%) button, pick a Common layouts configuration (which includes the openings-and-junctions allowance), or fill in the framing-fraction calculator. Note that a bare single-bay calculator figure with no openings allowance still carries the caution: a single bay excludes the extra timber around openings, corners and junctions. If you hold real evidence - a supplier's timber-percentage report for the build, or a whole-wall take-off from the consent drawings - record the demonstration under the caution, naming the evidence; it prints verbatim on the report and clears the warning. See the 38% rule.

The report flags my skylight or supplied floor R as unverified

Those values have no automatic backstop, so Thermly asks you to confirm them. For a skylight, record the U-value basis (R = 1/U_w) or pick a catalogue skylight, whose manufacturer-published whole-unit R carries its own provenance. For a supplied floor, enter the manufacturer and source document, and tick the confirmation that the calculator determines the value in accordance with H1/VM1 Appendix E. The value is used as entered; the flag is a prompt to confirm it. See Supplied floors and rafts.

Snapping is not doing what I expect

Snapping is per-source, and only your own drawn points snap out of the box - closing a zone on its first corner, or starting a wall where the last one ended. The plan-derived sources (intersections, plan lines, the detected grid) are deliberately opt-in, because a point jumping to geometry you did not draw is how a trace lands in the wrong place on a dense consent plan. Turn on exactly the sources you want from the plan-view Snap menu, or set defaults under Settings → Plan markup.

My glazing fails the cap

The Calculation Method applies only while wall glazing is 40% or less of the gross wall area (§2.1.2.5). Above it, H1 requires the Modelling Method (H1/VM1). Reduce glazing to bring it under the cap, or switch to the modelling pathway.

I cannot save, or the project is read-only

A Submitted project is locked against edits while it awaits sign-off: withdraw it to Draft to keep editing. An Approved project is final and locked - make a copy to revise it. A sample project is always read-only; make a copy of it. On a shared project, an organisation admin can also lock a project, or a colleague may be editing it: the page names them, and you can still view the project or make your own copy while they work. Wait for them to finish, or ask an organisation admin, who can take over.

I edited the project, but the report did not change

A report generated once a project is Submitted or Approved is frozen as a document of record, so generating it again returns the same PDF on purpose. To issue a changed report, withdraw the project to Draft, make and save the edits, and submit it again. While a project is a Draft or In Review, every report reflects the current state. See Revising and re-generating.

My work disappeared when the tab closed

It should not have: the H1 page autosaves as you work. Open the page again and Thermly offers the work back, as Resume unsaved draft? for a session you never saved, or Resume unsaved changes? for a saved project with newer autosaved edits. The indicator beside the project name shows when the draft was last autosaved, and says so if autosave is paused (on a locked project, for example, or after your session has expired).

The plan will not open, or a download link fails

Plan links are time-limited for security and expire after about five minutes. Re-open the plan (or reload the project) to get a fresh link. If a plan still will not open, try Replace to re-attach it.

A product is missing, or its R-value looks wrong

Use Custom R-value on the layer and enter the figure from the manufacturer's current datasheet with its basis. Check Show source to see what the catalogue value rests on, and send product feedback from the app. See Product sourcing and provenance.

An assembly I updated still shows its old build-up on a project

A saved project keeps a snapshot of each assembly as it was when assigned, so an old report stays reproducible after you refine your library. When the saved assembly has moved on, the row shows an amber Assembly updated chip: click Update to latest on the row, or Update all to refresh every such row at once. A row you have edited into its own copy is marked Edited copy and is never updated by itself; use ↩ reset from library on it if you want the library's version back.

Where is the insulation take-off?

In the report bar at the foot of the H1 page, next to Make Report, and a saved project's Dashboard card carries an Insulation button beside H1 Compliance. It needs the same inputs as the H1 report (climate zone, envelope areas, project name), so if it is disabled the tooltip lists what is still missing. It is free: it never spends a report credit.

An AI button is disabled

Hover it: the tooltip gives the reason. AI features may be switched off for your account (an administrator can switch them back on), or your monthly or daily AI allowance may be used up (they reset at the start of the month and at midnight UTC). The calculation, the report and AI Review's deterministic checks are unaffected. See Generating your insulation take-off.

Still stuck?

Use the Feedback link in the header - it opens a form where you can pick Bug, Suggestion, Question or Other and attach a screenshot. Your account email, the page you came from, your browser and the app version are included automatically; add the project name and what you expected versus what you saw.