ISO 9869-3:2023

INTERNATIONAL ISO
STANDARD 9869-3
First edition
2023-11
Thermal insulation of building
elements — In-situ measurement
of thermal resistance and thermal
transmittance —
Part 3:
Probe insertion method
Isolation thermique des éléments de construction — Mesurage in
situ de la résistance thermique et du coefficient de transmission
thermique —
Partie 3: Méthode par insertion d'une sonde
Reference number
© ISO 2023
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Published in Switzerland
ii
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 . 2
5.1 General . 2
5.2 Method without heat flow measurement . 2
5.3 Method with heat flow measurement . 2
6 Apparatus . 3
6.1 Temperature measuring devices . 3
6.1.1 Type of sensors and accuracy . 3
6.1.2 Sensor for measuring temperature distribution in walls . 3
6.1.3 Sensors for measuring surface and air temperatures . 4
6.2 Borescope . 4
6.3 Heat flow meter (HFM) . 5
7 Locations of the measured area and sensor installation . 5
8 Measurement conditions and period . 7
8.1 General . 7
8.2 Method without heat flow measurement . 7
8.3 Method with heat flow measurement . 7
9 Measurement procedure . 7
9.1 General . 7
9.2 Method without heat flow measurement . 7
9.3 Method with heat flow measurement . 8
10 Calculations . 9
10.1 Thickness of wall components . 9
10.2 Temperature distribution . 9
10.3 Thermal resistance . 9
11 Test report .10
Annex A (normative) Evaluation of the effect of thermal bridges on the sensor for
measuring the temperature distribution in the wall .12
Annex B (informative) Uncertainty analysis .18
Bibliography .21
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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This document was prepared by Technical Committee ISO/TC 163, Thermal performance and energy use
in the built environment, Subcommittee 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
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 flux per unit area and unit temperature difference in the steady state condition.
Since steady state conditions are never encountered on a site in practice, such a simple measurement is
not possible. Although various statistical methods have been introduced to address this problem, one of
the simplest is the use of 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 nature of the temperature difference between the surroundings on each of the sides thereof.
ISO 9869-1 describes the method 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 the simple mean and the sophisticated method of dynamic analysis
for steady state properties. This document describes a screening test of the insulation condition
and thermal resistance of existing building elements by visual observation with a borescope and by
measurement of the temperature gradient and heat flow with a temperature sensing rod and HFM.
Although the method used in this document is not a non-destructive inspection method, the diameter
of the borehole drilled through the building element is approximately less than 2 mm. The method
described in this document is intended for use as a practical diagnostic procedure 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 temperature
gradient through the building element and the heat flow rate. The thermal transmittance (thermal
resistance) of the insulation layer of the building components for the steady state condition can be
obtained by using the averages of the observed values over a certain period of time.
v
INTERNATIONAL STANDARD ISO 9869-3:2023(E)
Thermal insulation of building elements — In-situ
measurement of thermal resistance and thermal
transmittance —
Part 3:
Probe insertion method
1 Scope
This document describes a method for measuring the insulation performance of building elements, e.g.
exterior walls, floors, ceilings (hereinafter referred to collectively as "walls"). This is done by using
the probe insertion method, which gives the temperature distribution in the wall with a temperature
sensor in a small diameter borehole in the wall.
The measurement method is divided into a quantitative method, which measures the thermal resistance
with a heat flow measurement, and a qualitative method without heat flow measurement.
This document describes a screening test that is used for preliminary and practical diagnosis.
The method is applicable to plane building components with a light heat capacity, such as those in frame
structure dwellings. The measured results give the insulation performance at the local measurement
points rather than that of the whole panel including thermal bridges such as studs.
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 9869-1, Thermal insulation — Building elements — In-situ measurement of thermal resistance and
thermal transmittance — Part 1: Heat flow meter method
IEC 60584-1, Thermocouples−Part 1: EMF specifications and tolerances
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 terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
borescope
optical device consisting of a rigid or flexible tube with an eyepiece on one end and an objective lens
on the other end, linked together by a relay optical system in between, which is surrounded by optical
fibres used for illumination of the remote object
Note 1 to entry: Rigid or flexible borescopes may be fitted with an imaging or video device.
4 Symbols and units
Table 1 — Symbols and units
Symbol Quantity Units
k thermal conductivity W/(mK)
x depth from the inner surface of the building element m
L thickness of the insulation layer m
θ temperature °C
Q heat flow rate W/m
R thermal resistance (m K)/W
5 Principle
5.1 General
One of the two following methods shall be applied.
5.2 Method without heat flow measurement
A borehole with an approximately 1 mm diameter is drilled through the interior solid lining material (e.g.
Gypsum board). A borescope is inserted and the presence or absence of an insulation layer is confirmed
and the type and thickness of the insulation layer can also be observed. After visual inspection, a rod-
shaped temperature sensor is inserted, which measures the temperature distribution along the depth
of the borehole. The internal and external surface temperatures of the wall are also measured. Based
on these measurements, an illustration of the cross-sectional temperature distribution at that location
across the wall is made. Although the section temperature distribution obtained in the borehole is not an
exact representation of the temperature distribution of the insulation layer, the two-side temperature of
the insulation layer can be measured with a certain degree of accuracy. The degree of accuracy depends
on the conductance of the rod-shaped temperature sensor, the insulation layer and any other relevant
parts. The obtained temperature distribution shall be used as a basis for determining the quality of the
insulation layer as follows:
a) The thermal performance of the insulation material is evaluated from the ratio of the two-side
temperature difference of the insulation layer and that of the internal and external temperatures of
the wall (the observed building element).
b) The temperature distribution curve prepared based on the measurement results is compared with
the expected section temperature distribution assuming that the insulation material is functioning
properly. The discrepancy between the two temperature distribution curves provides diagnostic
criteria for determining whether, for example, the insulation layer is properly installed or not, or
whether the insulation layer has already experienced aging degradation or not.
5.3 Method with heat flow measurement
In addition to the method described in 5.2, the heat flow is measured at the indoor side surface of the
wall (building element). The thermal resistance of the insulation layer of the wall or the whole wall
is obtained as the quotient of the two-side temperature difference of the measured insulation layer
divided by the heat flow rate.
6 Apparatus
6.1 Temperature measuring devices
6.1.1 Type of sensors and accuracy
Thermocouples, resistance thermometers, or thermistors may be used to measure the temperatures
inside the wall, on the surface, and in the air. Thermocouples shall be type T and shall satisfy the
tolerance of class 1 described in IEC 60584-1. For resistance thermometers or thermistors, the error of
temperature measurement converted from the resistance tolerance shall be less than 0,5 °C.
6.1.2 Sensor for measuring temperature distribution in walls
The sensor shall have the following specifications with a rod-like thermometer:
a) The temperature sensor shall be coated.
b) The tip shall be processed in a needle-like shape, as shown in Figure 1, in order to penetrate the
insulation material without deforming the installed insulation layer. This type of sensor is already
manufactured and is commercially available for food processing applications. A temperature
sensor with a hard tube shell, as shown in Figure 2, can also be used. The tip of the tube shell shall
have a needle shape and the tube shell shall be hard enough to penetrate the insulation layer.
c) The diameter of the sensor rod, including the coating, shall be not more than 1,0 mm. The outer
diameter of the tube shell, if any, shall not exceed 1,3 mm.
d) The sensor rod shall have a scale indicating the insertion depth of the temperature sensing portion.
e) The sensor rod may have one or more than one temperature sensing portion. In sensor rods with
multiple sensing portions, the sensing portions shall be arranged at the same interval (not to exceed
15 mm) along the rod, as shown in Figure 3. Use of a sensor rod with more than one sensing portion
makes it possible to measure the temperature distribution along the borehole without traversing
the sensor.
f) The thermal bridge effect of the sensor-rod shall be small enough that the value of N obtained
c,nom
by the calibration method shown in Annex A (normative) is less than 0,5.
Key
1 temperature sensing portion
2 scale
3 diameter of sensor rod
Figure 1 — Temperature sensor with a needle-like shape (tip part)
Key
1 temperature sensing portion
2 scale
3 temperature sensor
4 tube shell
5 outer diameter of tube shell
Figure 2 — Temperature sensor with a hard tube shell (tip part)
Key
1 temperature sensing portions
2 interval of sensing portions
Figure 3 — Temperature sensor having multiple sensing portions (with a needle-like shape, tip
part)
6.1.3 Sensors for measuring surface and air temperatures
The sensors for measuring the surface and air temperatures shall be in accordance with ISO 9869-1,
except that thermistor sensors can also be used.
6.2 Borescope
A borescope is used to visually check the condition of insulation installation and the thickness of the
insulation layer in the wall (building element).
a) The borescope shall have an illumination device. The viewing angle shall be sufficiently wide and
the visual resolution shall be sufficiently fine to determine reliably whether insulation material is
present in the wall (building element) or not;
b) The borescope itself shall have a needle tip shape that can penetrate the insulation layer. A
borescope with a hard tube shell can be also used, as shown in Figure 4. The tip of the tube shell
shall have a needle shape and the tube shell shall be hard enough to penetrate the insulation layer;
c) The outer periphery of the borescope shall have a scale indicating the insertion depth;
d) The borescope shall have a diameter of not more than 1,5 mm, including the tube shell, and a length
greater than the thickness of the targeted wall (building element).
Key
1 scale
2 borescope
3 tube shell
4 diameter of borescope including tube shell
Figure 4 — Borescope with a hard tube shell (tip part)
6.3 Heat flow meter (HFM)
An HFM is required when measuring the thermal resistance of the insulation layer and shall be the
same as that described in ISO 9869-1.
7 Locations of the measured area and sensor installation
Figure 5 shows the schematic of the measured area and the measurement apparatus. The measured
area of the targeted wall (building element) shall be sufficiently larger than 400 × 400 mm and shall
face indoors. The measured area shall not include the frame section or other elements which cause
heat bridges. The measured area should be chosen in advance based on the drawings of the building or
thermal images acquired with an infrared camera.
The temperature sensor(s) on the internal and, if possible, on the external surface of the wall is (are)
installed in the vicinity of the centre of the measured area. When heat flow measurements are made,
an HFM shall also be installed in the vicinity of the centre on the interior surface of the wall. In addition
to the surface temperature measurement, temperature sensors shall also be installed in the room and
on the opposite side of the wall to measure the air temperature. If it is difficult to install a sensor on the
opposite side of the wall, for example, when measuring a floor or ceiling, the sensor shall be installed
outside the building in a well-ventilated area that is not affected by solar radiation.
The number of test positions for observing the interior of the wall with a borescope and measuring the
temperature distribution inside the wall shall be more than one, and the thermal conditions of all test
positions should be assumed to be the same. It is recommended that the test positions be separated
as far as possible from each other within the measured area. The distance between the borehole and
the HFM or the temperature sensor shall be not less than 50 mm. The distance between the frame
structure and the HFM, temperature sensor and the borehole shall be not less than 150 mm. The
temperature sensor incorporated in the HFM can also be used. Only one traverse with a temperature
sensor or borescope is allowed for each bore hole, except in cases where the insulation material proves
to be fibrous, in order to avoid air infiltration that can create an exchange between the cold and warm
surfaces. For example, in the case of foam-based insulation, at least four boreholes need to be provided
to obtain two measurement samples each from the borescope and the temperature sensor.
NOTE The size and homogeneity of the wall (building element) affects the number of measuring points and
the uncertainty of the method.
Installation of the apparatus, other than as noted above, shall be in accordance with ISO 9869-1.
Dimensions in millimetres
Key
1 test position 1 (borehole)
2 test position 2 (borehole)
3 HFM, temperature sensor
4 insulation
5 stud
6 interior
7 room temperature
8 external temperature
Figure 5 — Schematic of the test positions and apparatus
8 Measurement conditions and period
8.1 General
Test positions where the external surface is exposed to solar radiation shall be avoided. The room
temperature shall be controlled so that the temperature difference between the indoor and exterior
wall surfaces is more than 10 °C. It is recommended to maintain a constant room temperature for at
least 3 h before starting the temperature and heat flow measurements.
NOTE In order to estimate the required preheating time more accurately, it is helpful to calculate the time
constant of heat flow response to a step change in room temperature based on the assumed cross-sectional
configuration, using heat transfer simulation or other measures.
8.2 Method without heat flow measurement
The time and period of the test are not specified. However, the temperature distribution measured
during a period of large outdoor temperature change can be unsteady and can be affected by the heat
capacity of the wall.
8.3 Method with heat flow measurement
In order to reduce the influence of the thermal capacity of the wall, the test should be conducted at
night when temperature change is small, or the test should be conducted over multiple periods of 24 h.
The indoor air temperature variation should preferably be kept within 2 °C.
The electrical data from the HFM and temperature sensors shall be recorded continuously. The
maximum recording interval shall be 10 min. It is recommended that each recording be the average
value of several measurements sampled at shorter intervals, especially in the case of heat flow
measurements, in order to minimize the effect of heat flow fluctuations.
9 Measurement procedure
9.1 General
In this document, the tested wall (building element) is described as a single panel structure, such as
an insulation layer enclosed between two hard boards. However, the measurement method can also be
applied to other component types of walls. This document assumes only that the tested wall (building
element) consists of a hard layer where the boreholes are drilled and a soft layer where the borescope
or temperature sensor rod can be inserted without drilling.
9.2 Method without heat flow measurement
a) A small drilled borehole is provided at the test position of the indoor finishing hard board of the
wall (building element), such as a gypsu
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