You run a heat loss calculation. The answer is 4.2 kW. But where did the formula come from? What assumptions does it make? Which standard defines the methodology?
The problem
Most online calculators and spreadsheets give you a number with no source. You can't verify the methodology, you can't trace assumptions, and you can't defend the answer in a design review.
Why it matters for compliance
Building Regulations (Part L, Part F) and CIBSE guidance require that design calculations follow recognised methodologies. "I used an online calculator" isn't sufficient evidence. Refer to the current edition of the relevant standard for definitive requirements.
What source citation looks like
Every calculation should reference the standard, section, and method. Example: "Heat loss calculated per BS EN 12831 methodology. U-values per Part L 2021 Table 4. Internal design temperatures per CIBSE Guide A."
What MEP Desk does
Every calculator shows its source methodology, the formula used, and the relevant standard reference. When you export, the citation travels with the calculation.
For apprentices
Building this habit early makes you a more credible engineer. Know where your numbers come from.
MEP Desk's 61 calculators all show their source standards and formulas. Try it free.