Design verification for the «energy saving and thermal insulation» requirement: what the certified verifier actually checks

Among professionals who work with construction technical documentation, the phrase "requirement C" is often used for the energy part of a design. It is an easily explained confusion, but one worth correcting: the fundamental requirement related to energy has never carried the letter "c". In the list in article 5 of Law no. 10/1995 on quality in construction, the letter "c" designated "hygiene, health and the environment" (our translation), while "energy saving and thermal insulation" was, from the start, letter "f". A more recent fact should also be kept in mind, because it changes the legal basis to cite: with the entry into force of the Code of Spatial Planning, Urbanism and Construction (Law no. 169/2026), Law 10/1995 was repealed, except for art. 10 and 41 (art. 576 para. (3) lit. c) of the Code) — including art. 5, which contained the fundamental requirements. Of the old law, only art. 10 and art. 41 remain in force, with a technical-administrative role. The fundamental requirements are now found in art. 386 para. (3) of Law 169/2026, which keeps the seven from the old list (art. 5 para. (1) lit. a)-g) of Law 10/1995, including g) sustainable use of natural resources), at the same letters, and adds one: h) emissions into the external environment of constructions. Letter "f" — energy saving and thermal insulation — remains unchanged.

Who may verify designs on the energy requirement

The technical verification of designs on requirement "f" is a regulated activity, distinct from preparing the design and from energy certification. It may be carried out only by a design verifier certified by the ministry in this field, not by any engineer or architect who signs a design. The Regulation on the verification and technical expertise of designs, approved by Government Decision no. 925/1995, remains in force, expressly maintained by Law 169/2026 (art. 577 para. (5)) "until the date of its amendment" (our translation). The attestation of verifiers is based on Law 169/2026, art. 382 para. (1) and art. 448, plus the minister's order on attestation.

What has changed concretely with Law 169/2026 is the architecture of the verification itself: the code introduces four levels of design verification (NVP1-NVP4), correlated with the consequence classes of the construction (CC1-CC4), regulated in art. 440-444, with the verifier's obligations and liability set out in art. 445-446. For constructions in the lowest consequence class (CC1), art. 440 para. (3) provides that technical verification "is not necessary" (our translation); for CC2-CC4 it remains mandatory, with different depth at each level. Note: art. 277 para. (2) and (4) require verification of the technical design for thermal rehabilitation on requirement f (and on fire safety), which may operate as an exception to the rule for CC1; the text does not expressly settle the relationship between the two. At the most demanding level, NVP4, for constructions in class CC4, art. 444 introduces — in addition to the verification required at NVP3 — a parallel and independent calculation, carried out by the verifier with tools at least at the level of those used by the designer; if the differences in values exceed 5%, the design is revised and the verification is repeated after the revision. It is a much stricter control mechanism than merely confirming the coherence of a calculation summary, and it shows where the stakes of a verification on the energy requirement lead, in practice, for a building with major consequences.

What a verifier actually checks on the energy side

Regardless of the applicable verification level, the verifier's actual work on requirement "f" concentrates on a few recurring areas:

• Consistency with the calculation methodology in force. For buildings, the technical reference for calculating energy performance remains Mc 001-2022, and the verifier checks whether the calculation assumptions in the design (climate zoning, usage scenarios, characteristics of the envelope and of the installations) are applied according to the methodology, not merely plausible at first sight.
• Internal consistency of the calculation summary. A frequent error is not a wrong formula, but a discrepancy between the declared input data (areas, thermal resistances, installation efficiencies) and those actually entered in the calculation — or between the calculation summary and the drawn parts of the design.
• Consistency with the expected energy performance certificate. For designs that must demonstrate a certain energy class or nZEB compliance, the verifier checks whether the indicators in the summary actually support the conclusion declared in the design documentation, and do not merely state it.
• Traceability of assumptions. Every value entered in the calculation should come from a verifiable source — a standard, a product data sheet, a norm in force — not from a default value copied from a previous design without adaptation to the actual building.

Frequent errors found in verification

From a verifier's perspective, the most costly errors are usually not calculation errors as such, but consistency errors: a summary that uses a thermal resistance different from the one in the envelope details, an occupancy scenario that does not match the actual purpose of the building, a wrongly applied climate zone, or an outdated version of a regulation used without noticing that an update has meanwhile entered into force. Such errors are not visible on a quick reading of the conclusions — they come to light only in a line-by-line verification of the assumptions and formulas.

What assisted-verification software can speed up — and what it cannot do

A relatively new category of software tools aims to support precisely this stage: assisted verification of the coherence of a design, by automatically comparing the declared assumptions with the data actually used in the calculation, by flagging discrepancies between written and drawn parts, and by recalculating some indicators to compare the result with the one presented in the documentation. Such a tool can reduce the time spent on mechanical and repetitive checks — reading the rows of a summary, tracking a value through several documents — and can flag more quickly an inconsistency that the eye, at the fifth verification of the day, may miss.

What it cannot do — and this must be said explicitly — is replace the legal liability of the certified verifier. A result generated or confirmed by software has, in itself, no legal value in the process of technical verification of designs; the signature and stamp of the certified verifier remain the act that engages liability, not the output of a program. No software tool, however well calibrated, holds an official validation from MDLPA for the act of technical verification — such a validation does not even exist as a procedure, because verification remains, by law, an act of the certified person, not of a program. A useful tool is one that shortens the verifier's path to a reasoned conclusion, not one that hands it over ready-made.

The Zephren platform includes, for those who work with designs and energy performance certificates, an assisted-verification module designed to support this stage — useful both for energy auditors preparing their calculation summaries for handover and for verifiers looking for discrepancies more quickly in a design received for verification. Details about this module, alongside the rest of the functions for generating the energy performance certificate (CPE), are available at zephren.ro/program-de-calcul.