Thermal insulation -- Building elements -- In-situ measurement of thermal resistance and thermal transmittance

This document describes the infrared method for measuring the thermal resistance and thermal transmittance of opaque building elements on existing buildings when observing high emissivity diffuse surface using an infrared (IR) camera. This document demonstrates a screening test by quantitative evaluation to identify the thermal performance defect area of building elements. This document aims to measure the thermal transmittance (U-value) of a frame structure dwelling with light thermal mass, typically with a daily thermal capacity calculated according to ISO 13786 below 30 kJ/(m2K).

Isolation thermique -- Éléments de construction -- Mesurage in situ de la résistance thermique et du coefficient de transmission thermique

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Status
Published
Publication Date
15-Aug-2018
Current Stage
6060 - International Standard published
Start Date
09-Jun-2018
Completion Date
16-Aug-2018
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ISO 9869-2:2018 - Thermal insulation -- Building elements -- In-situ measurement of thermal resistance and thermal transmittance
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INTERNATIONAL ISO
STANDARD 9869-2
First edition
2018-08
Thermal insulation — Building
elements — In-situ measurement of
thermal resistance and thermal
transmittance —
Part 2:
Infrared method for frame structure
dwelling
Isolation thermique — Éléments de construction — Mesurage in
situ de la résistance thermique et du coefficient de transmission
thermique —
Reference number
ISO 9869-2:2018(E)
ISO 2018
---------------------- Page: 1 ----------------------
ISO 9869-2:2018(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2018

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

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Published in Switzerland
ii © ISO 2018 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 9869-2:2018(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and units ............................................................................................................................................................................................... 2

5 Principle ........................................................................................................................................................................................................................ 3

6 Requirements for apparatus .................................................................................................................................................................... 4

6.1 General ........................................................................................................................................................................................................... 4

6.2 Infrared camera ...................................................................................................................................................................................... 5

6.3 Heat transfer coefficient sensor ............................................................................................................................................... 6

6.4 ET sensor ..................................................................................................................................................................................................... 6

6.5 Thermocouple ......................................................................................................................................................................................... 6

6.6 Data logger ......... ......................................................................................................................................................................................... 6

7 Measurement method ..................................................................................................................................................................................... 6

7.1 Building ......................................................................................................................................................................................................... 6

7.2 Location of the measured area .................................................................................................................................................. 6

7.3 Measurement conditions ......... ....................................................................................................................................................... 7

7.4 Measurement of heat transfer coefficient ......... ............................................................................................................... 7

7.5 Measurement of environmental temperature ............................................................................................................. 7

7.6 Surface temperature distribution of building elements ...................................................................................... 8

7.7 Measurement time and measurement interval .......................................................................................................... 8

7.8 Measurement terms............................................................................................................................................................................ 8

7.9 Measurement period.......................................................................................................................................................................... 9

8 Calculations................................................................................................................................................................................................................ 9

8.1 Heat transfer area ................................................................................................................................................................................. 9

8.2 Calculation of heat flow rate........................................................................................................................................................ 9

8.3 Calculation of thermal transmittance...............................................................................................................................10

9 Measurement accuracy ...............................................................................................................................................................................10

10 Test reports .............................................................................................................................................................................................................10

Annex A (informative) Measurement principle .....................................................................................................................................12

Annex B (informative) Calculation of environmental temperature, structure of ET sensor ...................16

Annex C (informative) Structure and calibration of heat transfer coefficient sensor ....................................19

Annex D (informative) Uncertainty analysis .............................................................................................................................................24

Annex E (informative) The calculation example of uncertainty analysis ....................................................................27

Bibliography .............................................................................................................................................................................................................................31

© ISO 2018 – All rights reserved iii
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ISO 9869-2:2018(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following

URL: www .iso .org/iso/foreword .html.

This document was prepared by ISO/TC 163, Thermal performance and energy use in the built

environment, SC 1, Test and measurement methods.
A list of all parts in the ISO 9869 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2018 – All rights reserved
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ISO 9869-2:2018(E)
Introduction

The ISO 9869 series describes the in-situ measurement of the thermal transmission properties of plane

building components, primarily consisting of opaque layers perpendicular to the heat flow and having

no significant lateral heat flow. The thermal transmittance of a building element (U-value) is defined in

ISO 7345 as the “Heat flow rate in the steady state condition divided by area and by the temperature

difference between the surroundings on each side of a system”. Since steady state conditions are never

encountered on a site in practice, such a simple measurement is not possible and thereby some statistical

methods are introduced. One of the simplest methods is using the mean values over a sufficiently long

period of time. The required time for observation for reliable measurements depends on the thermal

properties of the building components and the natures of the temperature difference between the

surroundings on each side of them.

ISO 9869-1 describes the method which is used to estimate the thermal steady-state properties of a

building element from heat flow meter (HFM) measurements through plane building components.

Annex B describes the statistical methods of simple mean and the sophisticated method of dynamic

analysis method for steady state properties. This document, describes the calculation method for the

density of heat flow rate through both the evaluation of the internal surface thermal resistance and

the measuring of the temperature difference between the indoor surface temperature of the building

element and the indoor environmental temperature using an infrared camera (thermo-viewer). It

also describes the statistical methods of simple mean with less observing duration considering night

observation and building components with light heat capacity.

This document provides a preliminary and handy measuring method for the in-situ measurement of the

thermal transmission properties of plane building components and thereby the further simplifications

are applied compared with the method described in ISO 9869-1. The method described in this document

is expected as a method of a handy diagnostic method of the thermal transmission properties of plane

building components with light heat capacity such as those in frame structure dwelling.

The thermal performance of a part of the building element is evaluated by obtaining the heat absorption

(heat penetration) at the part of the indoor surface by multiplying the indoor total heat transfer

coefficient of the part surface by the difference between the part indoor surface temperature and the

indoor environmental temperature. The thermal transmittance (U-value) of the building components

for steady state condition can be obtained with the averages of the observed values over the certain

period of time.

The indoor surface temperature distribution of the building component is measured using an IR camera.

The indoor environmental temperature is measured by installing the environmental temperature

sensor (ET sensor) on the surface of the building component, and the indoor total heat transfer

coefficient of the surface of the building component is measured using a heat transfer coefficient sensor.

Even the indoor measurement is intended to be carried on with less influence of solar radiation so the

standard can be used on building elements on which indoor sides are not exposed to direct sunlight

through adjacent windows.
© ISO 2018 – All rights reserved v
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INTERNATIONAL STANDARD ISO 9869-2:2018(E)
Thermal insulation — Building elements — In-situ
measurement of thermal resistance and thermal
transmittance —
Part 2:
Infrared method for frame structure dwelling
1 Scope

This document describes the infrared method for measuring the thermal resistance and thermal

transmittance of opaque building elements on existing buildings when observing high emissivity diffuse

surface using an infrared (IR) camera. This document demonstrates a screening test by quantitative

evaluation to identify the thermal performance defect area of building elements.

This document aims to measure the thermal transmittance (U-value) of a frame structure dwelling

with light thermal mass, typically with a daily thermal capacity calculated according to ISO 13786

below 30 kJ/(m K).
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 7345, Thermal performance of buildings and building components — Physical quantities and definitions

ISO 8301, Thermal insulation — Determination of steady-state thermal resistance and related properties —

Heat flow meter apparatus

ISO 8302, Thermal insulation — Determination of steady-state thermal resistance and related properties —

Guarded hot plate apparatus

ISO 9869-1, Thermal insulation — Building elements — In-situ measurement of thermal resistance and

thermal transmittance — Part 1: Heat flow meter method
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 7345 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at https:/ /www.e lectropedia. org/
— ISO Online browsing platform: available at https:/ /www. iso. org/obp
3.1
thermography

image of a specific band of surface radiance detected with an infrared camera (3.2)

Note 1 to entry: On known and uniform high emissivity surfaces, with known and controlled irradiance from the

background, and with the proper instrument calibration and operator compensation, the radiance image can be

converted to a temperature distribution.
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ISO 9869-2:2018(E)
3.2
infrared camera

instrument that collects the infrared radiant energy from a target surface and produces an image in

monochrome (black and white) or colour, where the grey shades or colour hues are related to target

surface apparent temperature distribution
3.3
total heat transfer coefficient

sum of the convective heat transfer coefficient and the radiative heat transfer coefficient of the surface

of a building element

Note 1 to entry: It is assumed to be measurable using the heat transfer coefficient sensor.

3.4
heat transfer coefficient sensor

sensor to approximately measure the total heat transfer coefficient (3.3) of the surface of a building

element which can measure the total heat transfer coefficient in the neighbourhood of a section of the

building element
3.5
environmental temperature

conceptual temperature taking account of the indoor and outdoor air temperatures and radiant heat

of a building element used for calculating the thermal transmittance (thermal resistance) of the

building element

Note 1 to entry: A temperature measured by an environmental temperature sensor (3.6) is treated as the

environmental temperature.
3.6
environmental temperature sensor
ET sensor

sensor that takes an approximate measure of the indoor and outdoor environmental temperatures of a

building element to be measured
4 Symbols and units
Symbol Quantity Units
A heat transfer area of the region m
region area of the region with surface tempera-
A m
ture θ
h total heat transfer coefficient W/(m K)
θ environmental temperature °C
θ surface temperature °C
θ inside air temperature °C
inside environmental temperature of the region to
θ °C
be measured
outside environmental temperature of the region to
θ °C
be measured
θ surface temperature of section j °C
θ surface temperature of heat transfer coefficient sensor °C
θ plane radiant temperature of section j °C
Q heat flow rate W
q heat flow of the heat transfer coefficient sensor W/m
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ISO 9869-2:2018(E)
Symbol Quantity Units
r area ratio of the heat transfer area of section j —
R total thermal resistance (m K)/W
U thermal transmittance W/(m K)
5 Principle

This method (illustrated in Figure 1) measures the amount of irradiance of regions in contact with

the outside air from the surface temperature, total heat transfer coefficient and environmental

temperature. The difference between the inside and outside temperature is then used to determine

thermal transmittance/thermal resistance of the regions that are in a steady-state.

The amount of irradiance of regions in contact with the outside air when being heated is derived from

Formula (1) in relation to the inside temperature (Annex A).
Qh=−θθ A (1)

The amount of irradiance of the region can be determined using Formula (1) and the measurement of

the temperature of the inside surface temperature of the region made with an infrared camera, together

with the readings of the total heat transfer coefficient and environmental temperature obtained from

the heat transfer coefficient sensor and ET sensor mounted near the region. If the surface temperature

of the region being measured varies, the average temperature is used by taking the temperature of

each area of the region. This method defines the environmental temperature as a value approximately

measured by an ET sensor. The method to obtain the environmental temperature is shown in Annex B.

The amount of irradiance of the region is measured when it is in a constant state away from direct

sunlight at night for at least three hours, and calculated using Formula (2) and the difference between

the inside and outside environmental temperature.
U = (2)
θθ− ⋅A
ni ne
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ISO 9869-2:2018(E)
Key
1 measurement area
2 outside
3 inside
Figure 1 — Outline of measurement principle
6 Requirements for apparatus
6.1 General

The necessary apparatus for in-situ measuring thermal resistance and thermal transmittance are as

following:
6.1.1 Infrared camera.
6.1.2 Heat transfer coefficient sensor.
6.1.3 ET sensor.
6.1.4 Thermocouple thermometer.
6.1.5 Data logger.
Configuration of the apparatus is shown in Figure 2.
4 © ISO 2018 – All rights reserved
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ISO 9869-2:2018(E)
Key
1 measurement area
2 ET sensor
3 heat transfer coefficient sensor
4 IR camera
5 thermocouple
6 data logger
7 outside
8 inside
Figure 2 — Measurement outline (cross-section)
6.2 Infrared camera

Infrared cameras detect infrared radiation on the surface of the object being measured, with the

intensity distribution being displayed as a thermal image. The range of wavelength that can be

measured is the same as normal thermal radiation at 8 μm to 13 μm. The camera shall be capable of

detecting temperatures between the overall blackbody temperature range of at least −20 °C to 100 °C.

Thermal sensitivity shall not be worse than 80 mK on a 30° blackbody object temperature.

Measurements can be made at regular intervals for automatic logging of temperature. Infrared cameras

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ISO 9869-2:2018(E)

that come with software that processes and displays the measured temperature data as an image are

preferable.
6.3 Heat transfer coefficient sensor

The heat transfer coefficient sensor is used to estimate the total heat transfer coefficient of the surface

of the region of the object being measured. It has an insulating plastic foam backing and has a heating

sheet connected to a heat flow meter. The surface of the heating sheet is copper sheet, with the heat

flow meter attached to the front of the copper sheet. A sheet type electrical heater is used to heat the

copper sheet in a uniform fashion. The surface of the cooper sheet is finished with a matte black coating

(with an emittance greater than 0,9), and a thermocouple (with a diameter of less than 0,2 mm or a

thermocouple for surface measurements) is attached to the surface. The sensor shall have a size of

200 × 200 mm with a thickness of 25 mm as a standard.

Using the heat flow meter stretched on the heating sheet before building it into the heat transfer

coefficient sensor, calibrate the relation of the heat flow density to the output, following the procedure

specified in ISO 8301 or in ISO 8302. The structure and calibration of heat transfer coefficient sensor is

shown in Annex C.
6.4 ET sensor

The ET sensor is used to measure the environmental temperature of the regions of the object to be

measured. The size of the meter is approximately 200 × 200 mm with a thickness of 50 mm, consisting

of an insulating plastic foam and attached on the surface of copper sheet finished with a matte black

coating (with an emittance greater than 0,9). A thermocouple (with a diameter of less than 0,2 mm or a

thermocouple for surface measurements) is attached to the surface. The construction of the ET sensor

is shown in Annex B.
6.5 Thermocouple

The recommended temperature sensor is the type T thermocouple (copper/constantan) according to

IEC 60584-1 made from wire with diameter not greater than 0,25 mm. The temperature range available

consists of a standard temperature gauge and corrected for use with a data logger. If alternative sensors

are used, they should be at least as accurate as the above-mentioned, not subject to drift or hysteresis.

6.6 Data logger

The data logger automatically records the measured data of the temperature and heat flow from this

experiment with the required accuracy at regular intervals.
7 Measurement method
7.1 Building

The measurement object shall be a frame structure dwelling with a relatively small heat capacity [a

heat capacity per unit area of about 30 kJ/(m K) or less]. It is preferable if the details of the buildings

are researched thoroughly in advance using floorplans. Visual observations are made in-situ before the

measurements are made in order to select the appropriate regions for measurement.

7.2 Location of the measured area

The measurement position shall be selected according to the purpose of the test. The measured area

shall not be under the direct influence of either a heating or a cooling device or under the draught of a

fan. And the measurement area should be free of all visual interference from curtains, wall hangings,

furnishings, plants, light fixtures and anything that impedes the field of view for the IR imager.

6 © ISO 2018 – All rights reserved
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ISO 9869-2:2018(E)
7.3 Measurement conditions

The conditions of the measurement state that there must be a difference greater than 10 °C between the

inside and outside temperature when the heater is on. When the temperature differences is small, the

accuracy required for measuring this quantity may be lowered. The heating is achieved with the heater

that is used normally to keep the inside at a constant temperature. If there is no heating equipment, an

electrical heater with a fan can be used to heat the inside of the building. When stirring the air in the

room, take caution so that the airflow moving around the building element is not greatly different from

that under normal room conditions. The inside of the region to be measured must be completely sealed

by closing the building doors. If the room where the measurement takes place has openings such as a

sash window, block the window with curtains, shades, etc. to eliminate any temperature variation. In

the case of measurement conditions that are affected, such as infiltration, liquid water, moisture, air

leakage and other uncontrolled climatic conditions, this situation should be described in the report.

7.4 Measurement of heat transfer coefficient

The heat transfer coefficient sensor is mounted near the centre of the surface of the region to be

measured. Next, the power to the heat transfer coefficient sensor electrical heater is turned on and the

power adjusted so that the temperature of the surface of the sensor is between 2 and 4 °C higher than

the inside air temperature of the region to be measured.

The use of the heat transfer coefficient sensor is assumed that the measured values would correspond

to the plane averaged local total heat transfer coefficient over the testing building element. If there

are some reasons that this assumption cannot be stood, for examples, the testing building element

is vertically long enough and the local convective heat transfer coefficient will vary a lot from the

bottom to the top, a number of heat transfer coefficient number sensors may be arranged including

the centre. The variation of the measured values from the sensors might be recorded for the reference

purpose of the measurement reliability. The surface temperature of the heat transfer sensor shall be

preset to be the same as the difference (absolute value) between air temperature in the room where

the measurement takes place and a typical surface temperature of the section to be measured. The

temperature difference shall be higher than 2 °C.

Under the condition that the surface temperature of the heat transfer coefficient sensor is stable,

measure the following:

— Surface temperature of the heat transfer coefficient sensor measured by an infrared camera: θ

— Surface temperature of the ET sensor measured by an infrared camera (environmental

temperature: θ )

— Heat flow meter output on the surface of the heat transfer coefficient sensor (heat flow density: q)

The total heat transfer coefficient is calculated with Formula (3).
h= (3)
θθ−
hs ni

In addition, when the thermal performance of the building elements is low (e.g. in case of the differences

temperature between surface and air temperature are more than 2 K as an aim), the heat flow meter

(HFM) can be attached directly to the inside surface, and surface temperature of HFM is measured by

an infrared camera, and the total heat transfer coefficient can be calculated with Formula (3). Avoid

attaching the heat flow meter to any areas where a heat bridge may be formed. The surface should be

finished with a matte black coating (with an emittance greater than 0,9). When using a heat flow meter,

refer to ISO 9869-1.
7.5 Measurement of environmental temperature

The environmental temperature is measured with the ET sensor on both the inside and outside of

the building. The ET sensor on the inside of the building is mounted near the centre (but not attached

© ISO 2018 – All rights reserved 7
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ISO 9869-2:2018(E)

directly to the surface of the region) of the region to be measured. Measure the surface temperature

of the indoor ET sensor, first using a thermocouple, and then using an infrared camera. When the

resultant temperatures are different, adjust t
...

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