🏗️ Calculation of the thermal transmittance of windows and pedestrian doors (UW, UD, UWS) — from the contributions of glazing (Ug), opaque panels (Up), frame (Uf) and the linear thermal transmittance of the frame/glazing or frame/panel junction (Ψg, Ψp), also with closed shutters or external blinds, PN-EN ISO 10077-1

Construction PN-EN ISO 10077-1

Overview

WHAT THE STANDARD COVERS. Scope from the PKN catalogue card of PN-EN ISO 10077-1:2017-10 (Polish version) — the text on the card is cut off after the words “calculation of condens”; its content up to that point agrees with the scope of ISO 10077-1:2017, which we read in the sample: the document specifies methods for calculating the thermal transmittance of windows and pedestrian doors consisting of glazed or opaque panels in a frame, with or without shutters; it applies to different types of glazing (glass or plastic, single or multiple, with or without low-emissivity coatings, spaces filled with air or other gases), opaque panels, various frames (wood, plastic, metal with or without thermal barrier, metal with pinpoint metallic connections, combinations) and — where appropriate — the additional thermal resistance of closed shutters or external blinds depending on their air permeability. Roof windows and other projecting windows can be calculated by this method if Uf of their frames was determined by measurement or numerical calculation. Default values for glazing, frames and shutters are in the annexes; thermal bridges at the junction of the window or door frame with the rest of the building envelope are excluded. The calculation does not include: solar radiation, heat transfer from air leakage, condensation, ventilation of spaces in double and coupled windows or the surroundings of an oriel window; the standard does not apply to curtain walls and other structural glazing or to industrial, commercial and garage doors. We read the text in the sample of ISO 10077-1:2017 from the cover to 6.3.1.1 (input data — geometrical characteristics); we do not have the formulae for UW, UD and UWS (the rest of Clause 6) or Annexes A–G.

ACCORDING TO THE TEXT OF ISO 10077-1:2017 (foreword, introduction, Clauses 1–6.3.1.1). The standard was prepared by CEN/TC 89 “Thermal performance of buildings and building components” together with ISO/TC 163/SC 2 “Calculation methods” (Vienna Agreement); the third edition replaces ISO 10077-1:2006 as a minor revision for the set of EPB standards (energy performance of buildings) and incorporates corrigendum ISO 10077-1:2006/Cor.1:2009. Changes: removed from Clause 6 the boundary condition with the glazing replaced by a material of conductivity not exceeding 0,04 (the rules are in EN 12412-2), removed the determination of Ψg and Ψp by measurement according to EN 12412-2 (outside the scope of that standard), removed the formula for Ug (Ug according to ISO 10292), Formulae (1) and (2) extended for glazing bars, tabulated Ψ of glazing bars added, Annex C made normative (some values to two significant figures), Table C.2 and Annexes G and H moved to ISO/TR 52022-2, former Annex E moved to the main body. Introduction: the standard belongs to the EPB set (template of choices in Annex A, default choices in Annex B, possible national data sheets); main target group — window manufacturers; the alternative to calculation is testing the complete window or door by the hot box method according to ISO 12567-1 (roof windows — ISO 12567-2). Four components of the calculation: Ug of the glazing (EN 673 or measurement EN 674 or EN 675), Up of panels (ISO 6946 or ISO 10211, or measurement ISO 8301 or ISO 8302), Uf of the frame (ISO 10077-2, measurement EN 12412-2 or Annex D) and Ψ of the frame/glazing junction (ISO 10077-2 or Annex E); curtain walls — ISO 12631; doors for goods and vehicles — EN 13241-1. Symbols (4): A area (m²), R thermal resistance (m²·K/W), U thermal transmittance (W/(m²·K)), Ψ linear thermal transmittance (W/(m·K)), λ thermal conductivity (W/(m·K)); subscripts among others D door, W window, WS window with closed shutter, f frame, g glazing, gb glazing bar, p panel, sh shutter. Outputs (5.1): UW of a single window, UW of a system of two windows and of one frame with two sashes, UWS of a window with a closed shutter or external blind, UD of doors (fully glazed, with frame, glazing and panels, or without glazing). Description of the method (5.2): U of the product is calculated from the U of the components and their geometry and from the thermal interactions between them (lateral heat flow — linear thermal bridge — and surface and cavity resistances). Other topics (5.3): declared values for comparing products are calculated or measured for horizontal heat flow; design values for the actual inclination include it in Ug, while Uf and Ψ for the vertical position are used for all inclinations; the design value is calculated only if needed for calculating the energy demand of the building. Output data (6.1): UW, UD, UWS in W/(m²·K), validity interval 0 to ∞; calculations in steady state, independent of temperatures, wind and radiation (6.2).

STATUS (PKN catalogue cards as of 02.10.2026). The card of PN-EN ISO 10077-1:2017-10 (Polish version, published 17-07-2019, 52 pages, price group U) 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 10077-1:2017 [IDT], ISO 10077-1:2017 [IDT]”, “Replaces: PN-EN ISO 10077-1:2007 and PN-EN ISO 10077-1:2007/AC:2010 – Polish version”. The card of PN-EN ISO 10077-1:2007 (Polish version, 40 pages) has the “Withdrawn” header: withdrawal date 04-10-2017, “Replaced by: PN-EN ISO 10077-1:2017-10” (English and Polish versions). The PKN search engine (query “PN-EN ISO 10077-1”, 02.10.2026) shows the 2002, 2006 (d, e), 2007 and 2017-10 (e, p) editions. What changed for the result: according to the foreword — Formulae (1) and (2) now include glazing bars (their tabulated Ψ), Ug is calculated according to ISO 10292, and Ψ is not determined by measurement according to EN 12412-2; the formulae of the 2007 edition had no glazing bars.

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 10077-1 appears in 7 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 and AB 661 cite the 2017-10 edition, AB 1632 — “2017”, AB 1596 — the withdrawn 2007 edition, and AB 014 and AB 1054 — the designation alone without a date. The same 6 laboratories have PN-EN ISO 10077-2 in their scope. The “Laboratories” tab (“PN-EN ISO 10077-1”) 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 windows, doors, roof windows and shutters, doors and door leaves, described as a “calculation method” or “calculation test method” (in some laboratories with the marking “N”).

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. With the components: Uf of the frame taken from tables (Annex D) instead of from calculation according to PN-EN ISO 10077-2 or from measurement gives a value different from the real frame — the source of Uf has to be stated. With glazing bars: the 2017 edition extends Formulae (1) and (2) to glazing bars and gives their tabulated Ψ; the formulae of the 2007 edition did not include glazing bars — the result for a window with glazing bars calculated according to 2007 and 2017 need not be the same. With inclination: the declared value is for horizontal heat flow; the value for a roof window at its actual inclination takes the inclination into account only in Ug (5.3). With the scope: the UW figure does not include the thermal bridge at the frame/wall junction, air leakage or solar gains — it does not describe the losses of the window in the building as a whole. With the edition: AB 1596 cites the withdrawn 2007 edition.

WHAT WE DO NOT GIVE. We do not have the rest of Clause 6 (geometrical characteristics, formulae for UW, UD and UWS, shutter resistances) or Annexes A–G (EPB templates, default values of Ug, Uf, Ψ, shutter resistances) — so we give no formulae or default values.

Method principle

The thermal transmittance of a window or door is calculated from the thermal transmittances of the components — glazing (Ug), panels (Up) and frame (Uf) — and their geometrical characteristics, taking into account the thermal interactions between the components: lateral heat flow at the junction of the frame with glazing, panels and glazing bars (linear coefficients Ψ) and surface and cavity resistances (5.2); for a window with a closed shutter its additional thermal resistance is taken into account. Steady-state calculation, for horizontal heat flow.

Applications

• Windows, pedestrian doors, roof windows and shutters — UW, UD, UWS for declarations of performance; 6 laboratories in PCA scopes
• Calculations of the energy performance of buildings (EPB set of standards, ISO 52000-1)
• Comparison of glazing, frame and shutter variants at the product design stage

Key parameters

Standard

Standard number

PN-EN ISO 10077-1:2017-10 (wersja polska; EN ISO 10077-1:2017 IDT, ISO 10077-1:2017 IDT)

Title (PL)

Cieplne właściwości użytkowe okien, drzwi i żaluzji — Obliczanie współczynnika przenikania ciepła — Część 1: Postanowienia ogólne

Title (EN)

Thermal performance of windows, doors and shutters — Calculation of thermal transmittance — Part 1: General

Step-by-step procedure

1. Input data

   Collect the geometry of the product (areas, lengths of junctions) and U of the components with their source (calculation, measurement, table). PN-EN ISO 10077-1:2017-10 current (PKN cards as of 02.10.2026).

2. Glazing and panels

   Ug according to EN 673 / ISO 10292 or from measurement; Up according to ISO 6946 or ISO 10211.

3. Frame and junctions

   Uf and Ψ according to PN-EN ISO 10077-2 (numerical calculation) or from measurement (Uf) or from Annexes D and E; include glazing bars.

4. Calculation

   UW, UD or UWS according to the formulae of Clause 6 (we do not have their content), for horizontal heat flow; for shutters — additional resistance depending on air permeability.

5. Result

   Give the result with a description of the sources of the components and the reservation that it does not include frame/wall bridges, leakage and solar radiation.

Required equipment and apparatus

Health and safety (OHS)

• Calculation method — no laboratory hazards; the standard contains no safety warnings
• TECHNICAL NOTE: UW does not describe the heat losses of a window built into a wall (without the frame/wall bridge, infiltration and solar gains)

Frequently asked questions