Reading the H1 report

Whether you are looking at the live result on the H1 page or the generated PDF, the same structure applies: a headline verdict, the heat-loss comparison behind it, the hard-rule checks that apply regardless, and the advisory notes that help you trust the numbers.

The headline verdict

The overall verdict is Pass or Fail. It folds together the whole-building heat-loss comparison (§2.1.2.6) and the hard rules - the glazing cap (§2.1.2.5) and the minimum construction R-values (§2.1.2.11). If any hard rule fails, the headline fails, even when the heat-loss comparison passes on its own.

The heat-loss check

This is the core of the Calculation Method: your proposed building's heat loss must not exceed the reference building's for its climate zone. Three figures tell the story:

• Proposed (HL) - your building's heat loss, from Equation 2.1.
• Reference (HL) - the reference building's heat loss, from the Table 2.1.2.7 coefficients for the zone.
• Headroom - how much room you have (proposed under reference), as a value and a percentage. Positive headroom passes; negative fails.

Expand element breakdowns to see the contribution of each element (roof, wall, floor, glazing, door, skylight) on the proposed side, and the reference bucket it is compared against.

A construction R-value below its reference R is not a failure: the Calculation Method trades element against element, and the design complies on the total heat-loss comparison. The schedules deliberately do not colour a below-reference value red - red and amber are reserved for genuine warning states (failed minimums, applied defaults, values with no stated basis) so a compliant element is never dressed as a defect a checker would query.

Hard-rule checks

Some limits apply regardless of the heat-loss trade-off. Each is shown pass, fail, or not applicable:

• Glazing cap (§2.1.2.5) - wall glazing must be 40% or less of the gross wall area; above that, the Calculation Method does not apply.
• Minimum construction R-values (§2.1.2.11) - roof R2.6, wall R1.0, and floors other than slab-on-ground R1.3 (the clause expressly excludes slab-on-ground floors, which carry no minimum).
• Heated-element minimums (§2.1.2.12) - higher minimums where an element contains embedded heating (heating pipes or cables within the element or its finishes).

A construction can clear the heat-loss comparison and still fail a minimum, so these are surfaced separately. An assembly below its §2.1.2.11 minimum raises a blocking finding - stronger than a caution, because the figure is trustworthy and still not good enough: the clause binds identically in every climate zone (it is checked even before a zone is set) and sits outside the heat-loss comparison, so a surplus elsewhere cannot buy it back. It leads the calculator's warning rail and the report's Critical review items.

Advisory notes

These never change the verdict; they help you catch a take-off that does not add up:

• Take-off reconciliation - opening-versus-element sanity checks (for example, more glazing area than wall), and every missing R-value, named by its schedule tag - "A door (WA1-D2, 2.06 m²) has no R-value yet" - with the exact §2.1.2.13 default being used in the meantime (R0.18 for an opaque door, R0.15 for wall glazing and skylights). Those defaults are conservative; entering the real construction R-values will usually improve the result.
• Opening R-value plausibility (Appendix D) - flags a window, door or skylight R-value that looks out of range. An opening entered with an implausibly small R (below R0.01 - a decimal slip, say 0.005 typed for 0.5) gets the conservative default substituted so its heat loss is still counted, with a warning raised both live and on the report, so a typo can never silently drop an opening out of the calculation.

AI Review: the pre-flight check

The AI Review button beside AI plan summary in the report bar runs a one-click review of your current inputs and lists what to look at before generating: gaps (no climate zone, missing envelope elements, empty identity fields), compliance blockers (failed minimums, the glazing cap, a heat-loss comparison that does not pass), and risks (thin headroom, sub-38% wall framing without a recorded demonstration, incomplete build-ups, suspicious opening geometry).

The deterministic checks are free, work on unfinished projects (the gaps come back as findings rather than a refusal), and are computed server-side from a fresh compliance recomputation - the review reads exactly the warnings the report itself would print, so the two can never disagree. Each finding has a stable identity, a fixed severity and a clause pointer to verify against, in a floating window you can park beside the form.

On accounts with AI features, an AI pass joins in with the problems only judgement can catch: the plan's insulation spec disagreeing with your chosen build-ups, the window schedule not matching the openings you entered, elements the plan shows but the project lacks, a climate zone that does not fit the site address. The AI is deliberately boxed in - it reads a digest of engine-computed results, never calculates a number, and can only raise findings from the same fixed rulebook, so severities and clause citations are stamped by the application. AI-raised findings carry an AI tag, and the window says plainly that AI can make mistakes.

The review is advisory only - it never issues a compliance verdict, and nothing from it appears on the report PDF. It saves with the project and re-generates only when your inputs actually change, so reopening a project shows its last review instantly at no cost. The built-in sample project ships with a pre-computed review so every account can see the feature in full.

Critical review items on the report

The PDF carries an always-on Critical review items section: any blocking minimum-R finding first, then the material cautions - a supplied value with no stated basis, sub-38% framing without a recorded demonstration, plausibility flags. They are the reviewer's map of what to resolve before relying on or submitting the report. Each framed build-up card also declares its framing fraction and basis, and a downlight derate, where one applies, shows its working in the validation-warnings section.

Cross-referencing the PDF

The report is built to be checked against the plan. The Schedule of building elements lists each wall, roof and floor by its tag and name (WA1, RO1, FL1, SF1 …) - the same identifiers the plan captions and legend use - and each opening by its element-qualified tag (WA1-W2 is window W2 on wall WA1, your own plan tag carried through after the hyphen), so a reviewer reads a schedule row and goes straight to the same mark on the drawings. Each construction build-up card prints a colour bar matching the element's plan colour, so a reviewer can read a card and find the same-coloured element on the drawing at a glance. The header carries the project's save version and workflow status, the footer the Thermly version that generated it, and the optional revision history section lists the project's saved versions. The full section list is under Generating your H1 report.

Project status

A project's status travels with the report:

Status	Meaning
Draft	Working state; report carries a preview watermark.
In Review	Set aside for a check; still editable, still watermarked.
Submitted	Awaiting final sign-off; report prints without the watermark.
Approved	Locked. Copy it to revise.

Review comments are not tied to a status - colleagues on a shared project can comment against elements at any time, and a submitted project stays reviewable.

Next

• How Thermly calculates compliance - the method behind the numbers.
• Generating your H1 report.