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Verification

Check the working. See the evidence.

Every calculation we publish evidence for is listed here. Each page runs a fixed set of worked examples through the same calculation code our users run and compares the results, line by line, with the values printed in the standard.

Pages
12
Worked examples
127
Checks
374 of 374 pass

Published verification

Choose a calculation to inspect its fixed inputs, cited expected values and measured results. This is our own verification, not independent certification.

  • AHU duty psychrometrics to ASHRAE Fundamentals 2021 Chapter 1

    8/8 pass

    Heating, cooling and mixing of moist air against the worked examples printed in ASHRAE Fundamentals 2021 Chapter 1, and the Approved Document L fan power limit.

    Standards cited
    • Approved Document L, Volume 2: Buildings other than dwellings, 2026 edition
    • ASHRAE Handbook—Fundamentals 2021 (SI), Chapter 1 Psychrometrics
    Worked examples
    4
    Checks
    8
    Version / published
    v1.0 · 2026-09-28
    Engine fingerprint
    4017503a697e

    Open the worked examples

  • BS 7671 cable sizing

    65/65 pass

    Conductor selection, rating factors, voltage drop, earth-fault loop impedance and adiabatic conductor size against BS 7671 Appendix 4, Chapter 41, Chapter 54 and the IET On-Site Guide.

    Standards cited
    • BS 7671:2018+A4:2026
    • IET On-Site Guide 9th ed (2026)
    Worked examples
    16
    Checks
    65
    Version / published
    v1.4 · 2026-09-28
    Engine fingerprint
    c3b94d233cf2

    Open the worked examples

  • Ductwork to CIBSE Guide B2, Guide C and ASHRAE Fundamentals

    41/41 pass

    Duct fitting losses, circular equivalents, duct insulation, duct friction, duct sizing and louvre sizing against the worked examples and tables printed in CIBSE Guide B2 2016, CIBSE Guide C 2007 and the ASHRAE Handbook—Fundamentals 2021.

    Standards cited
    • ASHRAE Handbook—Fundamentals 2021 (SI)
    • CIBSE Guide B2 2016, Ventilation and ductwork
    • CIBSE Guide C 2007, Reference data
    Worked examples
    13
    Checks
    41
    Version / published
    v1.1 · 2026-09-29
    Engine fingerprint
    8747f047f32c

    Open the worked examples

  • BS 7671 earthing and fault current

    46/46 pass

    Earth-fault loop impedance, the Chapter 41 Zs limits, the Appendix 3 measured-Zs rule, protective-conductor sizing and prospective fault current against BS 7671 Chapters 41 and 54, Appendices 3, 4 and 14 and the IET On-Site Guide.

    Standards cited
    • BS 7671:2018+A4:2026
    • IET On-Site Guide 9th ed (2026)
    Worked examples
    16
    Checks
    46
    Version / published
    v1.1 · 2026-09-28
    Engine fingerprint
    42b07271a573

    Open the worked examples

  • Natural ventilation to CIBSE Guide A, BS EN 16798-7, ASHRAE and Approved Document F

    22/22 pass

    Wind and stack pressures, the cross, stack and single-sided flows, the purge and openable areas and the depth limits, against the worked examples, tables and equations printed in CIBSE Guide A 2015, BS EN 16798-7:2017, the ASHRAE Handbook—Fundamentals 2021, ASHRAE 62.1-2022, Approved Document F and CIBSE Guide B2.

    Standards cited
    • Approved Document F Volume 1, 2026 edition
    • ASHRAE Handbook—Fundamentals 2021 (SI)
    • ASHRAE Standard 62.1-2022
    • CIBSE Guide B2 2016, Ventilation and ductwork
    • CIBSE Guide A 2015, Environmental design
    • BS EN 16798-7:2017, Ventilation calculation methods
    Worked examples
    12
    Checks
    22
    Version / published
    v1.3 · 2026-09-30
    Engine fingerprint
    8512625f106b

    Open the worked examples

  • Solar PV yield to SAP 10.3 and MCS 032

    54/54 pass

    Annual solar radiation from SAP 10.3 Appendix U (Equations U1–U4, Tables U3–U5), annual yield from Equation M1 with the Table M1 overshading factors, the EREC G98 16 A per phase boundary, and the MCS 032:2025 standard estimate (kWp × Kk × SF) with its MGD 003 self-consumption look-up, against the standard's own worked examples.

    Standards cited
    • EREC G98 Issue 2 (2025)
    • MCS 032:2025 Issue 1.0 (01/01/2025), Solar PV & Battery: Pre-Sale Information and System Performance Estimate Standard
    • MCS Irradiance Datasets v2.0 (the kWh/kWp tables MCS 032 §3.1.2 reads)
    • SAP 10.3 (13-01-2026), The Government's Standard Assessment Procedure
    Worked examples
    21
    Checks
    54
    Version / published
    v1.1 · 2026-09-28
    Engine fingerprint
    bfecad71c34c

    Open the worked examples

  • Refrigeration loads and pipe sizing to ASHRAE and the IOR

    39/39 pass

    Refrigerated-facility loads (Chapter 24), refrigerant line sizing and riser oil return (Chapter 1) and freezing time (Chapter 20) against the worked examples printed in the ASHRAE Handbook—Refrigeration 2022, and the coldroom worked example in the Institute of Refrigeration's Good Practice Guide 150 (2026).

    Standards cited
    • ASHRAE Handbook—Refrigeration 2022 (SI)
    • Institute of Refrigeration, RACHP Engineering Technicians Section, Good Practice Guide 150: Calculating Heat Loads for Cold Stores (March 2026)
    Worked examples
    12
    Checks
    39
    Version / published
    v1.1 · 2026-09-27
    Engine fingerprint
    750860536b42

    Open the worked examples

  • Solar thermal hot water to MCS 024 and SAP

    54/54 pass

    The MCS 024:2025 solar heating performance estimate (SAP 2012 Appendix H with the standard's modified inputs: occupancy, daily demand, the modified solar-to-load ratio, EN 12976 collector defaults, the fuel saving by back-up heater) against the standard's printed tables and its Appendix B examples, and the SAP 10.3 Appendix H monthly worksheet against hand-worked examples.

    Standards cited
    • MCS 024:2025 Issue 1.0 (01/01/2025), Solar Heating Performance Estimate
    • MCS Technical Note: Calculation for Solar Thermal Total Installed Capacity v1.1
    • SAP 10.3 (13-01-2026), The Government's Standard Assessment Procedure, Appendix H
    • SAP 2012 version 9.92 (October 2013), Appendix H and Table 1b
    Worked examples
    13
    Checks
    54
    Version / published
    v1.0 · 2026-09-28
    Engine fingerprint
    df84f8eefac9

    Open the worked examples

  • Space heating and cooling loads to CIBSE Guide A and ASHRAE Fundamentals

    14/14 pass

    Steady-state heat loss, the cyclic-model cooling load and the radiant time series against the worked examples printed in CIBSE Guide A 2015 and the ASHRAE Handbook—Fundamentals 2021.

    Standards cited
    • ASHRAE Handbook—Fundamentals 2021 (SI)
    • CIBSE Guide A 2015, Environmental design
    Worked examples
    5
    Checks
    14
    Version / published
    v1.1 · 2026-09-29
    Engine fingerprint
    bcb2578cc95f

    Open the worked examples

  • Standalone fan power limits to Approved Document L Volume 2 (2026)

    6/6 pass

    The specific fan power limits the Standalone Fan calculation applies, against Table 5.9 of Approved Document L Volume 2.

    Standards cited
    • Approved Document L, Volume 2: Buildings other than dwellings, 2026 edition
    Worked examples
    3
    Checks
    6
    Version / published
    v1.0 · 2026-09-28
    Engine fingerprint
    ba5190d7e8d9

    Open the worked examples

  • Ventilation design rates to CIBSE Guide A, Approved Document F, HTM 03-01 and ASHRAE 62.1

    14/14 pass

    Outdoor-air rates, ventilation effectiveness, healthcare air-change rates and specific fan power limits against the printed tables.

    Standards cited
    • Approved Document F, Volume 2: Buildings other than dwellings, 2021 edition
    • Approved Document L, Volume 2: Buildings other than dwellings, 2026 edition
    • ANSI/ASHRAE Standard 62.1-2022, Ventilation and Acceptable Indoor Air Quality
    • Addendum j to ANSI/ASHRAE Standard 62.1-2022 (2024), incorporated in 62.1-2025
    • CIBSE Guide A 2015, Environmental design
    • HTM 03-01 Specialised ventilation for healthcare premises, Part A (2021)
    Worked examples
    8
    Checks
    14
    Version / published
    v1.2 · 2026-09-30
    Engine fingerprint
    7a4198511c4a

    Open the worked examples

  • Whole dwelling ventilation to Approved Document F Volume 1 (2026)

    11/11 pass

    Whole dwelling supply and wet-room extract rates against Tables 1.2 and 1.3 of Approved Document F Volume 1.

    Standards cited
    • Approved Document F, Volume 1: Dwellings, 2026 edition
    Worked examples
    4
    Checks
    11
    Version / published
    v1.0 · 2026-09-28
    Engine fingerprint
    7a4198511c4a

    Open the worked examples

How we verify

  • Fixed worked examples. Each case has fixed inputs and an expected value for every quantity it checks. Nothing is fitted to the engine.
  • Every expected value is cited to a printed page. It is either a value read from the standard's own table, or a hand calculation from printed values with the working shown.
  • Exact on tabulated values, ±2 % on calculated ones. A table lookup or a selected conductor size must match exactly. A quantity the engine calculates from tabulated inputs passes within ±2 %.
  • Re-run in CI on every engine change. The checks run automatically whenever the calculation code changes, and each page is regenerated from those results. A change that moves any result fails the build until the page is regenerated and reviewed.
  • Engine fingerprint per page. Each page carries a fingerprint of the calculation code its results came from, so a reader can tell whether the results are current.