SR EN 12831-1: the design heat load for heating and where Romanian regulations require it

Anyone searching for "SR EN 12831" usually has one of two problems: they are sizing a heating installation and need the recognised method for the required power, or they have found the standard cited in a normative and want to know whether it applies to them. This guide explains what the standard covers, how the national annex relates to it, and where Romanian legal acts require it. It does not reproduce the content of the standard, which is sold by ASRO.

What is SR EN 12831-1?

The title, as it appears in table 1.3 of Mc 001-2022 (position 21), is "Performanța energetică a clădirilor. Metodă de calcul al sarcinii termice de dimensionare. Partea 1: Necesarul de căldură pentru încălzire, Modul M3-3" (Energy performance of buildings. Method for calculation of the design heat load. Part one: Heat demand for heating, module). It is therefore the method by which the heating power needed by a space or a building is determined, so that the heating installation keeps the design indoor temperature under design outdoor conditions.

Part 3, SR EN 12831-3, is a different document: it concerns domestic hot water (modules M8-2 and M8-3) and is listed separately in Mc 001-2022, at position 40. It should not be confused with part 1.

How does the heat load differ from the annual energy demand?

The two quantities answer different questions. The design heat load is a power, expressed in kW: how much the installation must be able to supply at the most unfavourable design moment. It is used to choose the boiler, the heat pump, the heating emitters and the pipe diameters.

The annual energy demand for heating in the Mc 001-2022 balance is an energy, expressed in kWh per year, calculated with the monthly calculation method of chapter 2 of the methodology (§2.6-2.12; the monthly method proper at §2.7). It underlies the calculation of primary energy consumption, on which the energy class is assigned. Two buildings can have a similar annual demand and different peak loads, and the reverse, which is why one cannot be derived from the other by simple division.

Which documents supplement the standard in Romania?

The European standard was adopted as a Romanian standard. On top of it there is a national annex, SR EN 12831-1:2017/NA:2022, an original Romanian standard, approved in December 2022 (ASRO Standardization Bulletin no. 1/2023). Subsequently, in March 2024, ASRO approved the document SR EN 12831-1:2017/NA:2022/C91:2024, published in Standardization Bulletin no. 4/2024 in the section of approved standards; the bulletin does not specify the nature of the document. Anyone working with the national annex should check in the ASRO catalogue which version is in force, rather than rely on an old copy.

The European standard is under revision: the draft prEN 12831-1 was submitted to the CEN public enquiry (Standardization Bulletin no. 5/2025), with a voting deadline of 10 July 2025. Check in the ASRO catalogue whether a new edition has been adopted. Until it is possibly adopted as a Romanian standard, what applies in Romania remains the edition in force in the ASRO catalogue.

The text of the standard and of the national annex is purchased from ASRO. This guide does not reproduce them and cannot replace consulting them.

Where do Romanian regulations require the standard?

Normative I 13-2015 (heating installations). Through the amendment made by Order MDLPA no. 170/2023 (Official Gazette, Part I, no. 120 of 13.02.2023), art. 4.1 para. (1) provides that the nominal heating load of a space (room) is calculated according to SR EN 12831-1. Annex no. 2 to I 13 (the list of applicable standards), in the section "Standarde obligatorii" (Mandatory standards), includes the same standard at position 2. For an installation designer, this is the reference with direct effect: the power calculation per room is made according to the standard, not according to a method of one's own.

Mc 001-2022 (the methodology for calculating energy performance). Besides table 1.3, the standard appears in the text of the methodology in two places. At §2.1.1, the methodology announces a simplified calculation for elements in contact with the ground, "elaborat pe baza prevederilor din SR EN 12831-1" (developed on the basis of the provisions of SR EN 12831-1) (our translation). At §2.4.3, for the thermal parameters of elements in contact with the ground, the documents "normativul C107/5-2005, SR EN ISO 13370, SR EN 12831-1" (normative C107/5-2005, SR EN ISO 13370, SR EN 12831-1) (our translation) are recommended. For the auditor, the standard is therefore a recommended source for a specific chapter of the balance, not the method of the whole calculation.

Annex 2 to the energy performance certificate (CPE) also has the field "Necesarul de căldură de calcul (sarcina termică necesară)" (Design heat demand (required heat load)), expressed in kW, so the value is entered in the official model of the annex.

What happened to SR 1907-1?

The old Romanian standard for the design heat demand, SR 1907-1:2014, was withdrawn by ASRO in January 2025. Its situation, with the implications for old works and for ongoing projects, is covered in the guide SR 1907: design heat demand, which we do not repeat here.

Points to watch

• The heat load (kW) is confused with the annual demand (kWh/year). The class on the certificate is established on the basis of the second (through primary energy), and the sizing of the installation on the basis of the first; Annex 2 to the CPE records both.
• "EN 12831" is cited without part and without year. Part 1 (heating) and part 3 (domestic hot water) are different documents, and I 13 points to SR EN 12831-1.
• The European edition is used instead of the Romanian one. In Romania the Romanian standard applies, together with the national annex, from ASRO.
• The national annex and the document C91:2024 are ignored. Check in the ASRO catalogue what is in force at the date of the project.
• Mc 001-2022 is regarded as a sizing method. The methodology calculates energy performance; the sizing of the room remains with SR EN 12831-1, in accordance with I 13.
• A calculation made on SR 1907-1 is reused without stating that the standard has been withdrawn.

How a calculation program helps

Zephren calculates energy performance according to Mc 001-2022 and completes the certificate model and the annexes. It has no official validation from MDLPA and does not replace the responsibility of the auditor or the designer. The conformity of a heat load calculation with the text of the standard and with the national annex is established by the designer, on the copy purchased from ASRO. You can try the workflow in the Zephren calculation program. For the context of the energy balance, see the structure of the Mc 001-2022 methodology and how a CPE is calculated.

*Verified on 21 October 2026, against the text of Mc 001-2022 (official edition, MO no. 46 bis/17.I.2023), I 13-2015 as amended by Order MDLPA no. 170/2023 and the ASRO Standardization Bulletins 01/2023, 04/2024, 02/2025 and 05/2025. Courtesy translation; the Romanian version prevails. This is not technical or legal advice.*