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BRITISH STANDARD   BS EN ISO

10077-1:2000

Corrected and reprinted

 December 2001

The European Standard EN ISO 10077-1:2000 has the status of a BritishStandard

ICS 91.060.50; 91.120.10

NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW 

Thermal performance of  windows, doors and

shutters Ð Calculation

of thermal

transmittance ÐPart 1: Simplified method

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This British Standard, havingbeen prepared under thedirection of the Sector Committee for Building and CivilEngineering, was published under the authority of the StandardsCommittee and comes into effecton 15 September 2000

© BSI 10 December 2001

ISBN 0 580 32641 1

BS EN ISO 10077-1:2000

 Amendments issued since publication

 Amd. No. Date Comments

National foreword

This British Standard is the official English language version of EN ISO 10077-1:2000.It is identical with EN ISO 10077-1:2000.

The UK participation in its preparation was entrusted by Technical Committee

B/540, Energy performance of materials, components and buildings, toSubcommittee B/540/1, European Standards for thermal insulation, which has theresponsibility to:

Ð aid enquirers to understand the text;

Ð present to the responsible international/European committee any enquirieson the interpretation, or proposals for change, and keep the UK interestsinformed;

Ð monitor related international and European developments and promulgatethem in the UK.

 A list of organizations represented on this subcommittee can be obtained on requestto its secretary.

Cross-references

 Attention is drawn to the fact that CEN and CENELEC Standards normally includean annex which lists normative references to international publications with their corresponding European publications. The British Standards which implement theseinternational or European publications may be found in the BSI StandardsCatalogue under the section entitled ªInternational Standards CorrespondenceIndexº, or by using the ªFindº facility of the BSI Standards Electronic Catalogue.

 A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application.

Compliance with a British Standard does not of itself confer immunity 

from legal obligations.

Summary of pages

This document comprises a front cover, an inside front cover, the EN ISO title page, pages 2 to 31 and a back cover.

The BSI copyright notice displayed in this document indicates when this documentwas updated.

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EUROPEAN STANDARD

NORME EUROPÉENNE

EUROPÄISCHE NORM

EN ISO 10077-1

July 2000

ICS 91.060.50; 91.120.10

English version

Thermal performance of windows, doors and shutters -Calculation of thermal transmittance - Part 1: Simplified method

(ISO 10077-1:2000)

Performance thermique des fenêtres, portes et fermetures -Calcul du coefficient de transmission thermique - Partie 1:

Méthode simplifiée (ISO 10077-1:2000)

Wärmetechnisches Verhalten von Fenstern, Türen undAbschlüssen - Berechnung des

Wärmedurchgangskoeffizienten - Teil 1: VereinfachtesVerfahren (ISO 10077-1:2000)

This European Standard was approved by CEN on 21 July 1999.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Central Secretariat or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.

CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION

COMIT É E UROPÉ E N DE NORMAL ISAT ION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Central Secretariat: rue de Stassart, 36 B-1050 Brussels

 © 2000 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.

Ref. No. EN ISO 10077-1:2000 E

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Page 2EN ISO 10077-1:2000

Contents

Page

Foreword 3

Introduction 3

1 Scope 4

2 Normative references 5

3 Definitions, symbols and units 6

4 Geometrical characteristics 7

5 Calculation of thermal transmittance 9

6 Input data 15

7 Report 15

Annex A (normative) Internal and external surface thermal resistances 17

Annex B (informative) Thermal conductivity of glass 17

Annex C (informative) Thermal resistance of air spaces between glazing and thermaltransmittance of coupled or double glazing 18

Annex D (informative) Thermal transmittance of frames 20

Annex E (informative) Linear thermal transmittance of frame/glazing junction 25

Annex F (informative) Thermal transmittance of windows 26

Annex G (informative) Additional thermal resistance for windows with closed shutters 28

Annex H (informative) Permeability of shutters 29

Annex ZA (informative) A-deviations 31

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Foreword

The text of EN ISO 10077-1:2000 has been prepared by Technical Committee CEN/TC 89"Thermal performance of buildings and building components", the secretariat of which is heldby SIS , in collaboration with Technical Committee ISO/TC 163 "Thermal insulation".

This European Standard shall be given the status of a national standard, either by publicationof an identical text or by endorsement, at the latest by January 2001, and conflicting nationalstandards shall be withdrawn at the latest by January 2001.

For relationship with EU Directive(s), see informative Annex ZA, which is an integral part ofthis standard.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of

the following countries are bound to implement this European Standard: Austria, Belgium,Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy,Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the UnitedKingdom.

This standard is one of a series of standards on calculation methods for the design and

evaluation of the thermal performance of buildings and building components.

It contains two parts. Part 1 deals with the simplified calculation of the thermal transmittance

of windows and doors with or without shutters. Part 2 covers the numerical calculation (two-

dimensional) of the thermal transmittance of frame profiles.

Introduction

The method described in this standard is used to evaluate the thermal transmittance of

windows and doors, or as part of the determination of the energy use of a building.

An alternative to this calculation method is testing according to EN ISO 12567 “Thermal

performance of windows and doors – Determination of thermal transmittance by hot box

methods”.

In some countries the calculation of the thermal transmittance of windows forms part of their

national regulations. Information about national deviations from this standard due to

regulations are given in annex ZA.

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1 Scope

This standard specifies methods for the calculation of the thermal transmittance of windows

and doors consisting of glazed or opaque panels fitted in a frame, with and without shutters.

It allows for:

- different types of glazing (glass or plastics; single or multiple glazing; with or without

low emissivity coatings; with spaces filled with air or other gases);

- various types of frames (wood; plastic; metallic with and without thermal barrier;

metallic with pinpoint metallic connections or any combination of materials);

- where appropriate, the additional thermal resistance introduced by different types of

shutters, depending on their air permeability.

Curtain walls and other structural glazings, which are not fitted in a frame, are excluded fromthis standard. Roof windows are also excluded because of their complex geometrical frame

sections.

Default values for glazings, frames and shutters are given in the informative annexes. Thermal

bridge effects at the rebate or joint between the window or door frame and the rest of the

building envelope are excluded from the calculation.

The calculation does not include:

 – effects of solar radiation; – heat transfer caused by air leakage;

 – calculation of condensation;

 – ventilation of air spaces in double and coupled windows.

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2 Normative references

This standard incorporates by dated or undated reference, provisions from other publications.

These normative references are cited at the appropriate places in the text and the publicationsare listed hereafter. For dated references, subsequent amendments to or revisions of any of

these publications apply to this standard only when incorporated in it by amendment or

revision. For undated references the latest edition of the publications referred to applies.

EN 673 Glass in building – Determination of thermal transmittance (U  value) – 

Calculation method

EN 674 Glass in building – Determination of thermal transmittance (U value)

Guarded hot plate method

EN 675 Glass in building – Determination of thermal transmittance (U  value) – 

Heat flow meter methodprEN 1098 Measuring method for the determination of the thermal transmittance of

multiple glazing (U  value) – Calibrated and guarded hot box method

prEN 1279-1 Glass in building - Insulating glass units - Part 1: Generalities and

dimensional tolerances

prEN 1279-3 Glass in building - Insulating glass units - Part 3: Initial type testing on

gas-filled insulating glass units; gas leakage rate

prEN 12412-2 Windows, doors and shutters - Determination of thermal transmittance

by hot box method – Part 2: Frames

EN 12524 Building materials and products – Hygrothermal properties – Tabulated

design valuesEN ISO 6946 Building components and building elements – Thermal resistance and

thermal transmittance – Calculation method (ISO 6946)

EN ISO 7345 Thermal insulation – Physical quantities and definitions (ISO 7345)

prEN ISO 10077-2 Thermal performance of windows, doors and shutters - Calculation of

thermal transmittance - Part 2: Numerical method for frames

(ISO/DIS 10077-2)

EN ISO 10211-2 Thermal bridges in building construction - Calculation of heat flows and

surface temperatures - Part 2: Linear thermal bridges (ISO 10211-2)

ISO 8302 Thermal insulation – Determination of steady-state thermal resistance

and related properties – Guarded hot plate apparatus

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3 Definitions, symbols and units

3.1 Definitions

For the purposes of this standard, the definitions given in EN 673 and EN ISO 7345 apply.

In clause 4 of this standard, descriptions are given of a number of geometrical characteristics

of glazing and frame.

3.2 Symbols

Symbol Quantity Unit

 A area m2

 R thermal resistance m2·K/W

T  temperature KU  thermal transmittance W/(m2·K)

b width m

d  distance / thickness m

l length m

q density of heat flow rate W/m2

  linear thermal transmittance W/(m·K)

  thermal conductivity W/(m·K)

3.3 Subscripts

Figure 1 - Internal and external developed area

D door

W window

WS window with closed shutter  j summation index

d developed   p panel (opaque)

e external   s space (air or gas space)

f  frame   se external surface

g glazing   sh shutter

i internal   si internal surface

sa sash

 Ad,e

frame

 Ad,i

external

internal

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4 Geometrical characteristics

4.1 Glazed area, opaque panel area

The glazed area  Ag or the opaque panel area  Ap of a window or door is the smaller of the

visible areas seen from both sides, see figure 2. Any overlapping of gaskets is ignored.

4.2 Total visible perimeter of the glazing

The total perimeter of the glazing lg (or the opaque panel lp) is the sum of the visible perimeter

of the glass panes (or opaque panels) in the window or door. If the perimeters are different on

either side of the pane or panel then the larger of the two shall be used, see figure 2.

l gglass

l g

Ag

Figure 2 - Illustration of glazed area and perimeter

4.3 Frame areas

For the definition of the areas see also figure 3.

 Af,i Internal projected frame area

The internal projected frame area is the area of the projection of the internal frame on

a plane parallel to the glazing panel.

 Af,e External projected frame area

The external projected frame area is the area of the projection of the external frame

on a plane parallel to the glazing panel.

 Af  Frame area

The frame area is the larger of the two projected areas seen from both sides.

 Ad,i Internal developed frame area

The internal developed frame area is the area of the frame in contact with the internal

air (see figure 1).

 Ad,e External developed frame area

The external developed frame area is the area of the frame in contact with the

external air (see figure 1).

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4.4 Window area

The window area  Aw  is the sum of the frame area  Af  and the glazing area  Ag  (or the

panel area Ap).

A5 A6

Af,e

Aw

external

A7

A8

A4

A3A1

Af,i = Af Ag

internal

A2

frame(fixed)

sash(movable)

NOTE Af = max (Af,i ; Af,e)Aw  = Af + AgAd,i  = A1 + A2 + A3 + A4Ad,e = A5 + A6 + A7 + A8

Figure 3 - Illustration of the various areas

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5 Calculation of thermal transmittance

5.1 Windows

5.1.1 Single windows

frame(fixed)

glazing (singleor multiple)

sash(movable)

Figure 4 - Illustration of single window

The thermal transmittance of a single window U w shall be calculated using equation (1):

U  A U A U l

 A AW  

 

 

g g f f g g

g f 

 

(1)

where

U g is the thermal transmittance of the glazing;

U f  is the thermal transmittance of the frame;

  g is the linear thermal transmittance due to the combined thermal effects of glazing,

spacer and frame;

and the other symbols are defined in clause 4.

In the case of single glazing the last term of the numerator in equation (1) shall be taken as

zero (no spacer effect) because any correction is negligible.

When opaque panels are used instead of some of the glazing, U w is calculated as follows:

U  A U A U A U l l

 A A AW

g g p p f f g g p p

g p f 

 

 

 

 

(2)

where

U p is the thermal transmittance of the opaque panel(s);

  p is the linear thermal transmittance  for the opaque panel(s).

If the opaque panel is thermally bridged at the edge by a less insulating spacer, the effect of

the bridging shall be taken into account in the same way as for glazing; otherwise   p = 0.

NOTE Typical values of the linear thermal transmittance are given in annex E.

prEN ISO 10077-2 gives a method for calculating linear thermal transmittance.

prEN 12412-2 gives a method for measuring the linear thermal transmittance.

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5.1.2 Double windows

The thermal transmittance U W of a system consisting of two separate windows shall be

calculated by the following equation:

U U R R R U  

W

W si s se W

 

 

1

1 11 2 / / (3)

where

U W1, U W2 are the thermal transmittances of the external and internal window; respectively,

calculated according to equation (1);

 Rsi is the internal surface resistance of the external window when used alone;

 Rse is the external surface resistance of the internal window when used alone;

 Rs is the thermal resistance of the space between the glazing in the two windows.

Typical values of Rsi and Rse are given in normative annex A and of Rs in the informative annex

C.

NOTE If the gap exceeds 3 mm and measures have not been taken toprevent excessive air exchange with external air, the method does not apply.

glazing (singleor multiple)

external

internal

R se

R s

1 /U w1

R si

1 /U w

1 /U w2

frame(fixed)

sash(movable)

  

 3 mm

  

 3 mm

Figure 5 - Illustration of double window

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Page 11EN ISO 10077-1:2000

5.1.3 Coupled windows

The thermal transmittance U w of a systemconsisting of one frame and two separate

sashes shall be calculated using equation (1).To determine the thermal transmittance U g ofthe combined glazing equation (4) shall beused:

U U R R R U  

g  

 

1

1 1g1 si s se g2 / /   (4)

where

U g1 , U g2 are the thermal transmittances of the external and internal glazing; respectively,calculated according to equations (5) and (6);

 Rsi is the internal surface resistance of the external glazing when used alone;

 Rse is the external surface resistance of the internal glazing when used alone;

 Rs is the thermal resistance of the space between the internal and external glazing.

Typical values of Rsi and Rse are given in normative annex A and of Rs in the informative annex

C.

NOTE If the gap exceeds 3 mm and measures have not been taken toprevent excessive air exchange with external air, the method does not apply.

5.2 Glazing

5.2.1 Single glazing

The thermal transmittance of the single and laminated glazing, U g, shall be calculated with the

following equation:

sise

1

 Rd 

 R

U 

 j  j

 j

g

  

 

 

 

(5)

where

 Rse is the external surface resistance;

   j is the thermal conductivity of glass or material layer j;

d  j is the thickness of the glass pane or material layer j;

 Rsi is the internal surface resistance.

external

internal

  

 3 mm

glazing (single

or multiple)

Figure 6 - llustration of coupled windows

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5.2.2 Multiple glazing

The thermal transmittance of multiple glazing U g can be calculated according to EN 673 or by

means of the following equation:

si,sse

g

1

 R Rd 

 R

U 

 j

 j

 j  j

 j

  

   

 

 

(6)

where

 Rse is the external surface resistance;

   j is the thermal conductivity of glass or material layer j;

d  j is the thickness of the glass pane or material layers j;

 Rsi is the internal surface resistance;

 Rs, j is the thermal resistance of air space j.

NOTE Typical values of Rs are given in informative annex C.

5.3 Windows with closed shutters

A shutter on the outside of a window introduces an additional thermal resistance, resulting

from both the air layer enclosed between the shutter and the window, and the shutter itself

(see figure 7). The thermal transmittance of a window with closed shutters, U ws, is given by:

 RU U 

  

 

WWS

 / 1

1 (7)

where

U w is the thermal transmittance of the window;

 

 R is the additional thermal resistance due to the air layer enclosed between the shutter

and the window and the closed shutter itself (see figure 7).

external internal

shutter

 R 

 Rsh

EMBED 

Figure 7 - Window with external shutter

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The additional thermal resistance for five categories of shutter air permeability is given in the

following expressions:

 – shutters with very high air permeability:

 

 R = 0,08 m2

K/W (8)

 – shutters with high air permeability:

 

 R = 0,25  Rsh + 0,09 m2

K/W (9)

 – shutters with an average air permeability (for example solid wing shutters, wooden

venetian shutters with solid overlapping slats, roller shutters made of wood, plastic or

metal, with connecting slats):

 

 R = 0,55  Rsh + 0,11 m2

K/W (10)

 – shutters with low air permeability:

 

 R = 0,80  Rsh + 0,14 m2 K/W (11)

 – tight shutters:

 

 R = 0,95  Rsh + 0,17 m2

K/W (12)

where Rsh is the thermal resistance of the shutter itself.

The above equations are valid for Rsh < 0,3 m2

K/W. If no measured or calculated values for Rshare available, the typical values given in annexes G and H can be used. For external orinternal blinds use equations (8) to (12) with Rsh = 0.

NOTE 1 Annex H gives further information about the permeability of

shutters.

NOTE 2 The expression    R for tight shutters is the best current

estimate, and future developments may lead to other values.

5.4 Doors

 

frame(fixed)

glazing (single,or multiple)

sash(movable)

Figure 8 - Illustration of door with glazing

The thermal transmittance U D of a doorset, which is of similar design to a window, is obtained

using equation (13).

U   A U A U l A A

Dg g f f g g

g f 

 

 

 

 

(13)

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where  Af  ,  Ag and lg are defined in clause 4;

U g is the thermal transmittance of the glazing;

U f  is the thermal transmittance of the frame;

  g is the linear thermal transmittance due to the combined thermal effects oglazing

spacer and frame;

In the case of single glazing the last term of the numerator in equation (13) shall be taken as

zero (no spacer effect) because any correction is negligible.

frame(fixed)

opaque

panel

sash(movable)

Figure 9 - Schematic illustration of door with opaque panel

If the door consists of frame, glazing and opaque panels, then the following equation shall be

used:

U  A U A U AU l l

 A A AD

g g p p f f g g p p

g p f 

 

 

 

 

(14)

where

  Ap and lp are defined in clause 4;U p is the thermal transmittance of the opaque panel(s);

  p is the linear thermal transmittance for opaque panels.

If the opaque panel is thermally bridged at the edge by a less insulating spacer, the effect of

the bridging shall be taken into account in the same way as for glazing.

NOTE 1 Annex D gives typical values of U f  for different types of frame.

prEN ISO 10077-2 gives a method for calculating the linear thermal transmittance.

NOTE 2 Typical values of    are given in annex E.

The thermal transmittance of door leaves without a frame and without inhomogeneities

(having different layers only perpendicular to the heat flow direction) can be measured in the

guarded hot plate apparatus, in accordance with ISO 8302.

If the doorset does not have a design similar to a window system then the thermal

transmittance of the door leaves can be calculated in accordance with EN ISO 6946 provided

that the ratio of the thermal conductivities of any two different materials in the door does not

exceed 1:5 (screws, nails, and so on are excluded); this method includes the calculation of the

maximum relative error which should be less than 10 %.

If the maximum relative error is higher than 10 % or the ratio of the thermal conductivities of

the different materials is greater than 1:5 a numerical calculation in accordance with

prEN ISO 10077-2 and/or EN ISO 10211-2 should be carried out.

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6 Input data

The thermal transmittance of the frame, U f , is to be determined with the glazing replaced with

a material of thermal conductivity not exceeding 0,04 W/(m K), by hot box measurement or

numerical calculation in accordance with prEN ISO10077-2. The thermal transmittance of the

glazing, U g, is to be determined according to EN 673, EN 674 or EN 675. Both U f  and U g thus

exclude the thermal interaction between the frame and the glazing (or opaque panel), which is

taken into account by the linear thermal transmittance,   , either tabulated in this standard or

obtained by numerical calculations in accordance with prEN ISO 10077-2 or by measurement

in accordance with prEN 12412-2.

Other values to be used in the basic formulae can be obtained from annex A and

EN 12524 or by means of prEN 1098, EN ISO 6946 and ISO 8302.

If measured or calculated data are not available, the values in informative annexes B to H maybe used.

If the results are to be used for comparison of the performance of different windows, the

sources of the numerical values of each parameter shall be identical for each door or window

included in the comparison.

7 Report

The calculation report shall include the following.

7.1 Drawing of sections

A technical drawing (preferably scale 1:1) giving the sections of all the different frame parts

permitting verification of:

 – the thickness, height, position, type and number of thermal breaks (for metallic

frames);

 – the number and thickness of air chambers (for plastic frames only);

 – the presence and position of metal stiffening (for plastic frames only);

 – the thickness of wooden frames and the thickness of plastic and PUR–frame

(polyurethane) material; – the thickness of gas spaces, the identification of the gas and the percentage

assured to be present;

 – the type of glass and its thickness or its thermal properties and emissivity of its

surfaces;

 – the thickness and description of any opaque panels in the frame;

 – the internal projected frame area Af,i and the external projected frame area Af,e;–  the internal developed frame area Ad,i and the external developed frame area Ad,e

(only for metallic frames);

 – the position of the glass spacers or of the edge stiffening for opaque panels;

description of any shutters.

In the case of metallic frames with pin-point connections the distance between the pinpoints

shall be clearly indicated.

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7.2 Drawing of the whole window or door

A drawing of the whole window or door (seen from inside) with the following information:

 – glazed area Ag and/or opaque panel area A

p; – frame area: Af ; – perimeter length of the glazing lg and/or of the opaque panels lp.

7.3 Values used in the calculation

a) If the informative annexes are used this shall be clearly stated and reference shall be

made to the tables in the annexes.

b) If other sources are used to determine one or more of the U g , U f   and    values, the

sources shall be given. It shall be ascertained that these other sources use the samedefinitions of the areas Ag , Af  and of the perimeter length lg and lp.

c) If a glazing not covered by the table in the annex C is used, a detailed calculation

following EN 673 shall be given.

d) If measured or calculated values are used for one of the three parameters the

relevant standards shall be identified and it shall be confirmed that the values obtained

correspond to the definitions of the areas given in this standard.

7.4 Presentation of results

The thermal transmittance of the window or door, calculated according to the standard shall

be given with two significant figures.

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Annex A (normative)

Internal and external surface thermal resistances

For typical normal emissivities ( 

 0,8) for the inside and outside surfaces of the glazing, the

following values for the surface resistances Rse and Rsi shall be used.

Table A.1 - Surface thermal resistances

Window position Internal

 Rsim

2 K/W

External

 Rsem

2 K/W

Vertical or inclination    of the

glazing to the horizontal such that

90°           60°

0,13 0,04

 Rsi for special cases, for example a low emissivity coating on the outer surface of the interior

pane, can be calculated according to EN 673.

Annex B (informative)

Thermal conductivity of glass

In the absence of specific information for the glass concerned the value        1,0 W/(m K)

should be used.

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Annex C (informative)

Thermal resistance of air spaces between glazing and thermal transmittance ofcoupled or double glazing

Table C.1 gives some values of the thermal resistance  Rs  of air spaces for double glazing,

calculated according to EN 673. The data apply:

 – for vertical windows or an inclination    of the glazing to the horizontal such that

90 °           60°;

 – for spaces filled with air;

 – with both sides uncoated or with one side coated with a low emissivity layer;

 – for a mean temperature of the glazing of 283 K and a temperature difference of 15 K

between the two outer glazing surfaces.

For triple glazing the procedure in EN 673 should be used.

Table C.1 - Thermal resistance Rs of unventilated air spaces, in m2

K/W, for coupled and

double windows

Thickness of

air space  

One side coated with a

normal emissivity of:

Both sides

 uncoated

mm 0,1 0,2 0,4 0,8

6 0,211 0,190 0,163 0,132 0,127

9 0,298 0,259 0,211 0,162 0,154

12 0,376 0,316 0,247 0,182 0,173

15 0,446 0,363 0,276 0,197 0,186

50 0,406 0,335 0,260 0,189 0,179

100 0,376 0,315 0,247 0,182 0,173

300 0,333 0,284 0,228 0,171 0,163

For wide air layers like in double windows or doors the calculation according to EN 673 does

not lead to correct results. In such cases more sophisticated calculation methods or

measurements should be used.

Table C.2 gives the thermal transmittance U g of double and triple glazing filled with different

gases, calculated in accordance with EN 673.  The values of the thermal transmittance in the

table apply to the emissivities and gas concentrations given. For individual glazing units the

emissivity and/or gas concentration may change with time. Procedures for evaluating the

effect of ageing on the thermal properties of glazed units are given in prEN 1279-1 and

prEN 1279-3.

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Table C.2 - Thermal transmittance U g of double and triple glazing filled with different

gases

Glazing Type of gas space(gas concentration    90 %)

Type GlassNormal

emissivityDimensions

mm Air Argon Krypton SF6

Uncoated 4-6-4 3,3 3,0 2,8 3,0

glass 4-9-4 3,0 2,8 2,6 3,1

(normal 0,89 4-12-4 2,9 2,7 2,6 3,1

glass) 4-15-4 2,7 2,6 2,6 3,1

4-20-4 2,7 2,6 2,6 3,1

One pane 4-6-4 2,9 2,6 2,2 2,6

coated 4-9-4 2,6 2,3 2,0 2,7

glass 

0,4 4-12-4 2,4 2,1 2,0 2,74-15-4 2,2 2,0 2,0 2,7

4-20-4 2,2 2,0 2,0 2,7

One pane 4-6-4 2,7 2,3 1,9 2,3

Double coated 4-9-4 2,3 2,0 1,6 2,4

glazing glass   0,2 4-12-4 1,9 1,7 1,5 2,4

4-15-4 1,8 1,6 1,6 2,5

4-20-4 1,8 1,7 1,6 2,5

One pane 4-6-4 2,6 2,2 1,7 2,1

coated 4-9-4 2,1 1,7 1,3 2,2

glass   0,1 4-12-4 1,8 1,5 1,3 2,3

4-15-4 1,6 1,4 1,3 2,34-20-4 1,6 1,4 1,3 2,3

One pane 4-6-4 2,5 2,1 1,5 2,0

coated 4-9-4 2,0 1,6 1,3 2,1

glass   0,05 4-12-4 1,7 1,3 1,1 2,2

4-15-4 1,5 1,2 1,1 2,2

4-20-4 1,5 1,2 1,2 2,2

Uncoated 4-6-4-6-4 2,3 2,1 1,8 2,0

(normal) 0,89 4-9-4-9-4 2,0 1,9 1,7 2,0

glass 4-12-4-12-4 1,9 1,8 1,6 2,0

2 panes 4-6-4-6-4 2,0 1,7 1,4 1,6

coated   0,4 4-9-4-9-4 1,7 1,5 1,2 1,6

4-12-4-12-4 1,5 1,3 1,1 1,6

2 panes 4-6-4-6-4 1,8 1,5 1,1 1,3

Triple coated   0,2 4-9-4-9-4 1,4 1,2 0,9 1,3

glazing 4-12-4-12-4 1,2 1,0 0,8 1,4

2 panes 4-6-4-6-4 1,7 1,3 1,0 1,2

coated   0,1 4-9-4-9-4 1,3 1,0 0,8 1,2

4-12-4-12-4 1,1 0,9 0,6 1,2

2 panes 4-6-4-6-4 1,6 1,3 0,9 1,1

coated   0,05 4-9-4-9-4 1,2 0,9 0,7 1,1

4-12-4-12-4 1,0 0,8 0,5 1,1NOTE The values of thermal transmittance in the table were calculated using EN 673. Theyapply to the emissivities and gas concentration given. For individual glazing units the emissivityand/or gas concentrations may change with time. Procedures for evaluating the effect of ageingon the thermal properties of glazed units are given in prEN 1279-1 and prEN 1279-3.

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Annex D (informative)

Thermal transmittance of frames

Values of U f  evaluated by numerical calculation methods (finite element, finite difference) in

accordance with prEN ISO10077-2 can be used as input data for calculations, as can values

of U f  obtained by direct measurements using hot box methods in accordance with

prEN 12412-2.

If no other information is available, the values derived from the following tables and graphs

can be used in the calculations for the corresponding frame types.

All values given in this annex refer to the vertical position only. Typical values for common

types of frames are given in table D.1, figure D.2 and figure D.4, which can be used in the

absence of specific measured or calculated information for the frame concerned.

All the values shown in table D.1, figure D.2 and figure D.4 are based on a large number of

measured values as well as mathematically evaluated values determined using numerical

calculation methods. They include the effect of the developed areas.

Future development should not be impeded by tabulated U f  values. Values for frames which

are not described in the tables should be determined by measurements or calculations.

Especially in the case of aluminium profiles with thermal breaks1) there is the problem that the

thermal transmittance of the frame is influenced by different construction characteristics, such

as: – the distance a  between the aluminium sections;

 – the width b  of the material of the thermal break zones;

 – the conductivity of the thermal break material;

 – the ratio of the width of the thermal break to the frame projection width.

A thermal break can be considered as such only if it completely separates the metal sections

on the cold side from the metal sections on the warm side.

The values in this annex are based on Rsi = 0,13 m2

K/W and Rse = 0,04 m2

K/W.

It is common practice to produce "Profile Systems" comprising a large number of different

frames, having a wide range of geometric shapes but having similar thermal properties. This is

because in these groups of frames, the important parameters such as the size, material and

design of the thermal break, are the same. A document specifying practical procedures for

evaluating the thermal properties of such "profile systems" is under preparation.

 1) The values of U f in table D.1, figure D.2 and figure D.4 cannot be used for sliding windows but theprinciple of equation (1) can be used.

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Plastic frames

If no other data are available, the values in table D.1 can be used for frames without metal

reinforcements.

Table D.1 - Thermal transmittances for plastic frames with metal reinforcements

Frame material Frame type U f W/(m2 K)

Polyurethane with metal core

thickness of PUR    5 mm

2,8

PVC-hollow

profiles1)

two hollow chambers

2,2

three hollow chambers

2,0

 1)

 With a distance between wall surfaces of hollow chambers of at least 5 mm (refer to figure D.1).

Dimensions in millimetres

Figure D.1 - Hollow chamber in plastic frame

Other plastic profile sections should be measured or calculated.

 

 5

external

external

internal

internal

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Wood frames

Values for wood frames can be taken from figure D.2. For U f , the values correspond to amoisture content of 12 %. For definition of the thickness of the frame see figure D.3.

hard wood (density 700 kg/m3)   = 0,18 W/(m K)

soft wood (density 500 kg/m3) 

 = 0,13 W/(m

K)

Thickness of the frame d f  in mm

U f in (W/m

2

K)

2,0

1,0

3,0

15010050

Figure D.2 - Thermal transmittances for wooden frames and metal-wood frames (see figure D.3)depending on the frame thickness d f 

sash

frame

wood metal-wood metal-wood internal:

right side offrame section

external:left side offrame section

 d 1  d 1

 d 2  d 2  d 2

  d 1

2

21f 

d d d 

 

 

sash

frame

wood wood metal-wood

d d d  j j

f   

 

 sa f 

2

 d 1

d 3d 2

 d 1

d 3d 2

 d 1

d 4d 2 d 3

Figure D.3 - Definition of the thickness d f of the frame for various window systems

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Page 23EN ISO 10077-1:2000

Metal frames

The thermal transmittance of metal frames can be determined by measurement using hot boxmethods in accordance with prEN 12412-2 or by numerical calculation

 in accordance with

prEN ISO 10077-2. Values obtained by such methods should be used when available, in

preference to the method given in this annex.

If such data are not available, values of U f  can be obtained by the following procedure for:

- metal frames without a thermal break;- metal frames with thermal breaks corresponding to the sections illustrated in figure D.5

and figure D.6, subject to restrictions on the thermal conductivity and widths of thethermal breaks.

For metal frames without a thermal break, use U fo = 5,9 W/(m2·K).

For metal frames with thermal breaks, take U fo from the solid line in figure D.4.

4 0

3 0

2,0

0 4 8 12 16 20 24 28

U fo  in W/(m2·K)

32 36

Smallest distance between opposite metal sections, d , in mm

NOTE  The shaded area indicates the range of values obtained from manymeasurements on frames carried out in several European countries, derived from thesurface temperature difference across the frame.

Figure D.4 - U f0  -values for metal frames with thermal break

 The thermal resistance of the frame, Rf ,  is given by

17,01

f0f    

U  R (D.1)

and the thermal transmittance of the frame, U f , from

ed,ef,sef id,if,si  /  / 

1f   A A R R A A R

U   

  (D.2)

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where Ad,i, Ad,e, Af,i, Af,e, are the areas as defined in clause 4, expressed in square metres;

 Rsi is the appropriate internal surface resistance of the frame, in m2

K/W;

 Rse is the appropriate external surface resistance of the frame, in m2

K/W;

 Rf  is the thermal resistance of the frame section, in m2

K/W, resulting from the thermal

transmittance of the frame taking into account the appropriate surface resistance.U f0 is the thermal transmittance, in W/(m

2 K), calculated as if the developed area were

equal to the projected area.

 d  is the smallest distance between

opposite aluminium sections of

the thermal break; b j is the width of thermal break  j;

 bf  is the width of the frame.

f 0,2bb j

 j         

Thermal conductivity of thermal

break materials

0,2

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Annex E (informative)

Linear thermal transmittance of frame/glazing junction

The thermal transmittance of the glazing, U g, is applicable to the central area of the glazing

and does not include the effect of the glass spacers at the edge of the glazing. On the other

hand, the thermal transmittance of the frame, U f , is applicable in the absence of the glazing.

The linear thermal transmittance    describes the additional heat conduction due to the

interaction between frame, glazing and spacer. The linear transmittance    is mainly effected

by the conductivity of the spacer material. For aluminium and steel (not stainless steel) glass

spacers table E.1 indicates the values of    for a specific range of types of frames and glazing.

Table E.1 - Values of the linear thermal transmittance,   

 2 ), for aluminium and steel (not stainless

steel) glass spacers

Frame material Double or triple glazing,

uncoated glass,

air or gas space

 

W/(m·K)

Double glazing with low emissivity,

triple glazing with two low emissivity

coatings, air or gas space

 

W/(m·K)

Wood frame and

plastic frame

0,04 0,06

Metal frame with

thermal break

0,06 0,08

Metal frame without

thermal break

0 0,02

Values for spacers not covered by the table can be determined by numerical calculation in

accordance with prEN ISO 10077-2.

 2) These values are evaluated for double glazings with low emissivity, U g     1,3 W/(m

2 K) and triple

glazing with low emissivity U g     0,7 W/(m2

K).

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Annex F (informative)

Thermal transmittance of windows

Table F.1 and table F.2 give typical values calculated by the method in this standard using

linear thermal transmittances from annex E. Values for windows with other frame area

fractions can be evaluated by means of the equations of the main part of that standard.

Table F.1 - Thermal transmittances for windows with fraction of the frame area 30 % of the whole

window area

Type of

glazing

U g

W/(m   K)

U f  

W/(m  K)

frame area 30 %

1,0 1,4 1,8 2,2 2,6 3,0 3,4 3,8 7,0

Single 5,7 4,3 4,4 4,5 4,6 4,8 4,9 5,0 5,1 6,1

3,3 2,7 2,8 2,9 3,1 3,2 3,4 3,5 3,6 4,4

3,1 2,6 2,7 2,8 2,9 3,1 3,2 3,3 3,5 4,3

2,9 2,4 2,5 2,7 2,8 3,0 3,1 3,2 3,3 4,1

2,7 2,3 2,4 2,5 2,6 2,8 2,9 3,1 3,2 4,0

2,5 2,2 2,3 2,4 2,6 2,7 2,8 3,0 3,1 3,9

2,3 2,1 2,2 2,3 2,4 2,6 2,7 2,8 2,9 3,8

Double 2,1 1,9 2,0 2,2 2,3 2,4 2,6 2,7 2,8 3,6

1,9 1,8 1,9 2,0 2,1 2,3 2,4 2,5 2,7 3,5

1,7 1,6 1,8 1,9 2,0 2,2 2,3 2,4 2,5 3,3

1,5 1,5 1,6 1,7 1,9 2,0 2,1 2,3 2,4 3,2

1,3 1,4 1,5 1,6 1,7 1,9 2,0 2,1 2,2 3,1

1,1 1,2 1,3 1,5 1,6 1,7 1,9 2,0 2,1 2,9

2,3 2,0 2,1 2,2 2,4 2,5 2,7 2,8 2,9 3,7

2,1 1,9 2,0 2,1 2,2 2,4 2,5 2,6 2,8 3,6

1,9 1,7 1,8 2,0 2,1 2,3 2,4 2,5 2,6 3,4

Triple 1,7 1,6 1,7 1,8 1,9 2,1 2,2 2,4 2,5 3,3

1,5 1,5 1,6 1,7 1,9 2,0 2,1 2,3 2,4 3,2

1,3 1,4 1,5 1,6 1,7 1,9 2,0 2,1 2,2 3,1

1,1 1,2 1,3 1,5 1,6 1,7 1,9 2,0 2,1 2,9

0,9 1,1 1,2 1,3 1,4 1,6 1,7 1,8 2,0 2,8

0,7 0,9 1,1 1,2 1,3 1,5 1,6 1,7 1,8 2,6

0,5 0,8 0,9 1,0 1,2 1,3 1,4 1,6 1,7 2,5

NOTE The calculation has been made using   -values according to annex E. Values for windows

with frame area fractions not equal to 30 % have to be evaluated by means of the equations of the

main part of the standard.

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Table F.2 - Thermal transmittances for windows with fraction of the frame area 20 % of the whole

window area

Type ofglazing

U g

W/(m   K)

U f 

W/(m  K)

frame area 20 %

1,0 1,4 1,8 2,2 2,6 3,0 3,4 3,8 70

Single 5,7 4,8 4,8 4,9 5,0 5,1 5,2 5,2 5,3 5,9

3,3 2,9 3,0 3,1 3,2 3,3 3,4 3,4 3,5 4,0

3,1 2,8 2,8 2,9 3,0 3,1 3,2 3,3 3,4 3,9

2,9 2,6 2,7 2,8 2,8 3,0 3,0 3,1 3,2 3,7

2,7 2,4 2,5 2,6 2,7 2,8 2,9 3,0 3,0 3,6

2,5 2,3 2,4 2,5 2,6 2,7 2,7 2,8 2,9 3,4

2,3 2,1 2,2 2,3 2,4 2,5 2,6 2,7 2,7 3,3

Double 2,1 2,0 2,1 2,2 2,2 2,3 2,4 2,5 2,6 3,1

1,9 1,8 1,9 2,0 2,1 2,2 2,3 2,3 2,4 3,0

1,7 1,7 1,8 1,8 1,9 2,0 2,1 2,2 2,3 2,8

1,5 1,5 1,6 1,7 1,8 1,9 1,9 2,0 2,1 2,6

1,3 1,4 1,4 1,5 1,6 1,7 1,8 1,9 2,0 2,5

1,1 1,2 1,3 1,4 1,4 1,5 1,6 1,7 1,8 2,3

2,3 2,1 2,2 2,3 2,4 2,5 2,6 2,6 2,7 3,22,1 2,0 2,0 2,1 2,2 2,3 2,4 2,5 2,6 3,1

1,9 1,8 1,9 2,0 2,0 2,2 2,2 2,3 2,4 2,9

Triple 1,7 1,6 1,7 1,8 1,9 2,0 2,1 2,2 2,2 2,8

1,5 1,5 1,6 1,7 1,8 1,9 1,9 2,0 2,1 2,6

1,3 1,4 1,4 1,5 1,6 1,7 1,8 1,9 2,0 2,5

1,1 1,2 1,3 1,4 1,4 1,5 1,6 1,7 1,8 2,3

0,9 1,0 1,1 1,2 1,3 1,4 1,5 1,6 1,6 2,2

0,7 0,9 1,0 1,0 1,1 1,2 1,3 1,4 1,5 2,0

0,5 0,7 0,8 0,9 1,0 1,1 1,2 1,2 1,3 1,8

NOTE The calculation has been made using   - values according to annex E. Values for windows

with frame area fractions not equal to 20 % have to be evaluated by means of the equations of the

main part of the standard.

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Annex G (informative)

Additional thermal resistance for windows with closed shutters

When the thermal resistance of the shutter itself, Rsh, is known (by calculation or by

measurement) the additional thermal resistance,    R, should be obtained using the appropriateexpression in 5.3. Table G.1 gives some typical values of shutter thermal resistance and thecorresponding values of

 

 R, which can be used in the absence of values of Rsh obtained frommeasurement or calculation.

Table G.1 - Additional thermal resistance, 

 

 R, for windows with closed shutters

Shutter type Typical

thermal

resistance of

shutter Rsh

m2

K/W

Additional thermal resistances

at specific air permeability of the

shutters 1)

   Rm

2 K/W

High air

permeability

Average air

permeability

Low air

permeability

Roller shutters of

aluminium0,01 0,09 0,12 0,15

Roller shutters of

wood and plastic

without foam filling

0,10 0,12 0,16 0,22

Roller shutters of

plastic with foam

filling

0,15 0,13 0,19 0,26

Shutters of wood,

25 mm to 30 mm

thickness

0,20 0,14 0,22 0,30

 1)

The definition of the air permeability of shutters is given in annex H.

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Annex H (informative)

Permeability of shutters

For the different types of shutter, the permeability criterion can be expressed in terms of an

effective total gap bsh between the shutter and its surround according to figure H.1.

shb b b b  1 2 3 (H.1)

where b1 , b2 and b3 are the average edge gaps at the bottom, top and side on the shutter (seefigure H.1).

b3 is included for one side only, since gaps at the side influence the permeability less than thegaps at the top and bottom.

b 3

internal

external

b 2

b 1

shutter

b 2

b 1

external internal

b 3

Figure H.1 - Definition of edge gaps

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Table H.1 - Relationship between permeability and effective total edge gap between shutter andits surround

Class Permeability of shutter  bsh

mm

1 Very high permeability bsh > 35

2 High air permeability 15    bsh < 35

3 Average air permeability 8    bsh < 15

4 Low air permeability bsh     8

5 Tight bsh     3 and b1+b3=0 or b2+b3= 0

NOTE 1 For permeability classes 2 and above, there should be no openings within theshutter itself.

NOTE 2 For shutters of permeability class 5 the following criteria apply:

a) Roller shutters

The edge gaps at the sides and the bottom are considered equal to 0 if strip gaskets are

supplied in the guide rails and the final lath, respectively. The gap at the top is considered

equal to 0 if the entrance to the roller shutter box is fitted with lips - or brush-type joints on

both sides of the curtain or if the end of the curtain is pressed by a device (spring) against

a sealing material at the inner surface of the outer side of the roller shutter box.

b) Other shutters

Effective presence of strip gaskets on three sides and the gap at the fourth side less than

3 mm.

An alternative method to establish that a shutter is class 5 is to verify by measurement that the

air flow through the shutter is less or equal than 10 m3 /(h m

2) under a pressure drop of

10 Pa.

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Annex ZA (informative)

A-deviations

A-deviation: National deviation due to regulations, the alteration of which is

for the time being outside the competence of the CEN/CENELEC member.

This European Standard does not fall under any Directive of the EC.

In the relevant CEN/CENELEC countries these A-deviations are valid instead ofthe provisions of the European Standard until they have been removed.

Clause Deviation

6 Germany: Verordnung über einen energiesparendenWärmeschutz bei Gebäuden (Wärmeschutzverordnung -WärmeschutzV) Vom 16. August 1994.

The German regulation specifies that the design thermaltransmittance for glazing as well as windows and windowdoors shall be in accordance with tables 2 to 6 ofDIN V 4108-4:1998-10.

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BS EN ISO10077-1:2000

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