🏗️ Calculation of the thermal transmittance of window and door frame profiles (Uf), shutter boxes (Usb) and the linear thermal transmittance of the frame/glazing or frame/panel junction (Ψg, Ψp) — two-dimensional numerical method according to ISO 10211, radiosity method or single equivalent thermal conductivity of cavities, validation of the software, PN-EN ISO 10077-2

Construction PN-EN ISO 10077-2

Overview

WHAT THE STANDARD COVERS. Scope from the PKN catalogue card of PN-EN ISO 10077-2:2017-10 (Polish version), in full (our translation): “This document specifies a method and gives reference input data for the calculation of the thermal transmittance of frame profiles and of the linear thermal transmittance of their junction with glazing or opaque panels. The method can also be used to evaluate the thermal resistance of shutter profiles and the thermal characteristics of roller shutter boxes and similar components (e.g. blinds). This document also gives criteria for the validation of numerical methods used for the calculation. This document does not include effects of solar radiation, heat transfer caused by air leakage or three-dimensional heat transfer such as pinpoint metallic connections. Thermal bridge effects between the window frame and the building structure are not included. NOTE Table 1 in the Introduction shows the relative position of this document within the set of EPB standards in the context of the modular structure as set out in ISO 52000-1”. Scope of the card of amendment PN-EN ISO 10077-2:2017-10/A1:2025-06 (English version), in full (our translation): “6.4.2.4.1, B.3, F.2, H.2, H.3, I.2 modified”. We read the text of the standard in the sample of ISO 10077-2:2017 from the cover to 6.3.2 (thermal conductivity values — up to the requirements for measurement); we do not have the rest of Clause 6 (among others cavities, boundary conditions, calculation of Uf and Ψ), Clauses 7 and 8 or the annexes, and we did not read the text of amendment A1.

ACCORDING TO THE TEXT OF ISO 10077-2:2017 (foreword, introduction, Clauses 1–6.3.2). The standard was prepared by CEN/TC 89 together with ISO/TC 163/SC 2 (Vienna Agreement); the third edition replaced ISO 10077-2:2012 after a technical revision for the set of EPB standards and incorporated corrigendum ISO 10077-2:2012/Cor 1:2012. In Clause 6 a new approach to cavities was added, conduction/convection were separated from radiation and the radiosity method was introduced; Annexes G and H were added. Scope (1) — as on the card. References (2): ISO 7345, ISO 10211, ISO 10292, ISO 10456:2007, ISO 12567-2:2005, ISO 17025 (sic — as in the text, without “IEC”), ISO 52000-1, EN 673, EN 12519. Symbols (4): A, b (width perpendicular to the heat flow), d (depth along the heat flow), C (constant in the Nusselt number formula), E (intersurface emittance), F (view factor), h (heat transfer coefficient), L2D (two-dimensional thermal conductance), Nu, q, R, T, U, σ, ε, λ, Ψ, Θ; subscripts among others f frame, g glazing, p panel, sb shutter box, eq equivalent. Outputs (5.1): Uf of a frame profile, Usb of a shutter box, Ψg of the frame/glazing junction and Ψp with a panel. Principle (5.2): calculation with a two-dimensional numerical method conforming to ISO 10211, with a subdivision into elements so fine that further subdivision does not significantly change the result (criteria in ISO 10211); two approaches to cavities: a) radiosity method — conduction/convection and radiation calculated in parallel and separately; b) single equivalent thermal conductivity method λeq — including conduction, convection and radiation, depending on the geometry of the cavity and adjacent materials (NOTE: this is the method of ISO 10077-2:2012); for assigning λeq, vertical orientation of frame sections and cavities is assumed irrespective of the actual orientation of the window, also for roof windows. Validation of software (5.3): calculate the examples of Annexes G and H (radiosity method) or I (λeq) and meet all requirements; the calculated L2D for the cases of Annex H or I shall not differ from the values in Tables H.3 and H.4 or I.3 and I.4 by more than ± 3 %, giving an accuracy of U and Ψ of about 5 %. Output data (6.1): Uf and Usb in W/(m²·K), validity interval > 0…20; Ψ in W/(m·K), −20…20; steady-state calculations (6.2). Geometry (6.3.1): cross-sections of the frame profile, box and junctions from the manufacturer; profile extensions overlapping the wall or other elements (e.g. Z- or H-profiles) are disregarded (Figure 1) — an approximation for U, not appropriate for assessing condensation risk; in the calculation of the window U according to ISO 10077-1 the extension is also disregarded. Conductivity (6.3.2): from Table D.1, from tables in ISO 10456, from product standards, from technical approvals or from measurement according to an appropriate International Standard; measurement only when there are no tabulated, product or approval data; measurement at a mean temperature of 10 °C, in an accredited laboratory (according to ISO 17025) on samples conditioned at 23 °C and 50 % RH to constant mass (change not more than 0,1 % over 24 h); the measured value must account for material variability and uncertainty — e.g. a declared value from at least three samples from different lots (the rest of this requirement is not in the sample).

STATUS (PKN catalogue cards as of 02.10.2026). The card of PN-EN ISO 10077-2:2017-10 (Polish version, published 07-10-2019, 82 pages, price group X) has no “Withdrawn” header: Sector of Construction and Building Structures, KT 179 Thermal Protection of Buildings, ICS 91.120.10 and 91.060.50, “Introduces: EN ISO 10077-2:2017 [IDT], ISO 10077-2:2017 [IDT]”, “Replaces: PN-EN ISO 10077-2:2012” (English and Polish versions) and its corrigendum AC:2012. The card of amendment PN-EN ISO 10077-2:2017-10/A1:2025-06 (English version, published 27-06-2025, 28 pages, price group N) has no “Withdrawn” header, “Introduces: EN ISO 10077-2:2017/A1:2025 [IDT], ISO 10077-2:2017/Amd 1:2024 [IDT]”. The card of PN-EN ISO 10077-2:2012 (Polish version, 44 pages) has the “Withdrawn” header: withdrawal date 04-10-2017, “Replaced by: PN-EN ISO 10077-2:2017-10”. The PKN search engine (query “PN-EN ISO 10077-2”, 02.10.2026) shows the 2005, 2012 (e, p), 2017-10 (e, p) editions and amendment A1:2025-06. What changed for the result: the 2017 edition compared with 2012 — the radiosity method alongside λeq and new validation examples G and H; amendment A1:2025 modifies 6.4.2.4.1, B.3, F.2, H.2, H.3 and I.2 — clauses on cavities, data and validation examples — but we do not know the content of these changes.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, data up to 17.09.2026, read 02.10.2026). The number 10077-2 appears in 11 records of 6 laboratories: AB 014, AB 035, AB 661, AB 1054, AB 1596, AB 1632. In the current scopes on the PCA website (read 02.10.2026, issues from 19.11.2025 to 02.09.2026) AB 035, AB 661, AB 1596 and AB 1632 cite the 2017-10 edition, AB 014 and AB 1054 — the designation alone without a date; none adds amendment A1:2025-06. The “Laboratories” tab (“PN-EN ISO 10077-2”) shows the same 6 laboratories — checked with a query of the tab on the labcoda.pl production server on 02.10.2026.

WHAT THE LABORATORIES TEST (PCA entries). “Thermal transmittance” of window and door frame sections of wood, plastics, metals or combinations, shutter profiles and roller shutter boxes, “calculation method” (in some with the marking “N”); the same laboratories have PN-EN ISO 10077-1 for calculating UW of the whole window.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. With the software: a result from software that has not passed the validation cases (L2D within ± 3 %) is not a result according to the standard (5.3). With the mesh: too coarse a subdivision changes the result — convergence criterion from ISO 10211 (5.2). With cavities: the standard allows two methods (radiosity and λeq), each with its own validation cases — the method used has to be stated; λeq is always assigned for the vertical position of the section, also in roof windows (5.2). With profile extensions: they are disregarded for U, but the same model is not suitable for assessing condensation (6.3.1, Note 1). With materials: conductivity from measurement only in the absence of tabulated and product data — and at 10 °C, after conditioning at 23 °C and 50 % RH (6.3.2). With the scope: Uf does not include solar radiation, air leakage or three-dimensional bridges from pinpoint metallic fasteners.

WHAT WE DO NOT GIVE. We do not have the rest of Clause 6 (cavities, formulae for Uf and Ψ, boundary conditions, surface resistances), Clauses 7–8, Table D.1 or validation Annexes G, H, I (Tables H.3, H.4, I.3, I.4), and we did not read amendment A1:2025 — so we give no formulae, resistances, tabulated conductivities or L2D reference values.

Method principle

The cross-section of the frame profile (and its junction with glazing or a panel) is modelled two-dimensionally and the heat flow is solved numerically according to ISO 10211 under specified boundary conditions; from the calculated two-dimensional thermal conductance L2D, Uf of the profile and the linear coefficient Ψ of the frame/glazing or frame/panel junction are determined; heat transfer in cavities is treated with the radiosity method or with the equivalent conductivity λeq, and the software is checked on the validation cases of the standard.

Applications

• Window and door frame profiles (wood, PVC, aluminium with thermal break, steel, combinations) — Uf and Ψ for declarations of performance; 6 laboratories in PCA scopes
• Roller shutter boxes and shutter profiles — Usb and thermal resistance (scope of the standard)
• Input data for calculating UW of the window according to PN-EN ISO 10077-1

Key parameters

Standard

Standard number

PN-EN ISO 10077-2:2017-10 (wersja polska; EN ISO 10077-2:2017 IDT, ISO 10077-2:2017 IDT) z PN-EN ISO 10077-2:2017-10/A1:2025-06 (wersja angielska)

Title (PL)

Cieplne właściwości użytkowe okien, drzwi i żaluzji — Obliczanie współczynnika przenikania ciepła — Część 2: Metoda komputerowa dla ram

Title (EN)

Thermal performance of windows, doors and shutters — Calculation of thermal transmittance — Part 2: Numerical method for frames

Step-by-step procedure

1. Geometry

   Reproduce the profile cross-section from the manufacturer; disregard extensions overlapping the wall (Z-, H-profiles). PN-EN ISO 10077-2:2017-10 with A1:2025-06 current (PKN cards as of 02.10.2026).

2. Materials

   Conductivities from tables or product standards; measurement only in the absence of data — at 10 °C, in an accredited laboratory, after conditioning at 23 °C and 50 % RH.

3. Cavities

   Choose the radiosity method or λeq; assign λeq for the vertical position of the section; details according to Clause 6 (we do not have its content).

4. Calculation

   Convergent mesh according to the ISO 10211 criteria; calculate L2D and from it Uf, Usb or Ψ (we do not have the formulae).

5. Validation and result

   Software checked on cases G and H or I (L2D ± 3 %); state the cavity method and the sources of conductivity.

Required equipment and apparatus

Health and safety (OHS)

• Calculation method — no laboratory hazards; the standard contains no safety warnings
• TECHNICAL NOTE: a model with disregarded profile extensions is not suitable for assessing condensation risk

Frequently asked questions