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Moisture performance of a new thermal insulation composite for interior application


Abstract and Figures

The paper introduces prototypes of a new composite insulation product for interior application. The product consists of a standard mineral fibre insulation batt, which is wrapped in a combination of a thin fabric of moisture absorbing, capillary active material and vapour retarding membranes. The insulation composite has been tested with small samples in a laboratory setup and in an outdoor field test on a full-scale brick wall, and has so far shown promising results in comparison with other products. The paper describes the new insulation composite and the initial moisture tests that have been made with its constituents as well as results from the laboratory and field tests of its ability to prevent moisture accumulation.
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* Corresponding author:
Moisture performance of a new thermal insulation composite for
interior application
Carsten Rode1,*, Naja Kastrup Friis1, Christian Pedersen1, Nickolaj Feldt Jensen1
1Technical University of Denmark, Department of Civil Engineering, 2800 Kgs. Lyngby, Denmark
Abstract. The paper introduces prototypes of a new composite insulation product for interior
application. The product consists of a standard mineral fibre insulation batt, which is wrapped in a
combination of a thin fabric of moisture absorbing, capillary active material and vapour retarding
membranes. The insulation composite has been tested with small samples in a laboratory setup and
in an outdoor field test on a full-scale brick wall, and has so far shown promising results in
comparison with other products. The paper describes the new insulation composite and the initial
moisture tests that have been made with its constituents as well as results from the laboratory and
field tests of its ability to prevent moisture accumulation.
1 Introduction
In order to preserve the exterior aesthetics of an existing
outer wall, thermal insulation is often applied on the
inside of walls of historic buildings when they are energy
renovated, despite of the fact that in cold climates, interior
insulation incurs a
risk of moisture accumulation at the
interface between the original wall and the installed
insulation. For this reason, a lot of research has been
invested in recent years in the topic of interior insulation
of historical buildings, e.g. the European project RIBuild
[1], which has dealt exactly with renovation by interior
insulation of building from before 1945. A recent PhD
study [2] investigated interior insulated solid brick walls
in a setup where 24 similar walls with different interior
insulation systems were tested side by side
– 16 of them
facing south-west and 8 facing north-east.
The insulation system tested can be seen as an
alternative to the mineral wool based system with interior
polyethylene vapour retarder, which has traditionally
been used in Denmark. The traditional system only works
well if very good care
is paid to ensure a tight vapour
retarder, which may be difficult to realise in practice. In
some cases, a tight vapour retarder is exactly not desired,
since it might prevent moisture to escape, e.g. if it comes
from the outside after rain and solar driven inward drive.
Instead, diffusion open systems could be advocated for, as
they permit too high moisture contents in the insulation
systems to escape towards the interior, when conditions
are amenable. However, in a Nordic climate the caveat is
that it incurs a risk of significant moisture accumulation
at the interface between the interior insulation and the
original, solid outer wall, which is now colder.
Some insulation systems have been developed, or in
some cases been revitalized from the past, that facilitate a
movement of moisture from the cold side of the insulation
towards the warm indoor side. Such systems comprise
very lightweight aerated concrete, calcium silicate, and
cellular foam insulation system such as polyurethane or
phenolic insulation. T
he foam insulation systems may be
manufactured with narrow channels of calcium silicate
that permit suction of water back from the cold to the
warm side of the insulation board, such as iQ-Therm [3].
As demonstrated for instance in [2], even the diffusion
open systems with possible capillary active properties
cannot ensure a moisture safe solution. Their good
performance depends of course on the severity of the
indoor and outdoor boundary conditions, but can also be
enhanced by the use of hydrofobing agents on the outdoor
façade. Moisture sensible wooden elements in the
such as beams and laths, may be protected by strategically
positioned thermal bridges. However, this paper will not
study the use of hydrofobing agent or thermal bridges any
A somewhat related problem exists for insulation of
cold pipe systems where the continuous keeping of a cold
temperature and vapour tight surface at the pipe leads to
the risk of moisture built up over time in the coldest inner
part of the insulation, when the dew-point of the ambient
is above the pipe temperature. The traditional solution has
been to use rather vapour tight, closed foam insulation,
but practice shows that it only delays, but do not eliminate
the problem. Korsgaard invented the so-called
HygroWick system [4] to alleviate such problems. A non-
woven fabric or glass-fibre felt with capabilities to
function as a wick is wound around the cold pipe, see
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Fig. 1, left. After making a turn around the pipe, the fabric
is led through the slit of the pipe-section, which can be
made of a diffusion open material such as mineral wool.
The outside of the pipe section has an outer jacket of
vapour tight material, and a small piece of the fabric
should be led out of the pipe section to the ambient, where
it can be attached to the outer surface of the vapour tight
jacket. The jacket keeps moisture ingress into the system
slow, but nevertheless, when moisture accumulates on the
pipe, it will be absorbed by the fabric so it functions as a
wick that transports the moisture to the outside of the pipe.
The principle has proven functional and is today a
commercial system [5]. There are variations of the
, which keep the wick away from frost if the pipe
temperature is below 0°C. It is also possible to put an extra
jacket on the complete outside of the system to make it
suitable for used in rooms where hygienic requirements
do not permit the potentially wet fabric to be exposed.
These variations of the system are functional, too.
Inspired by the situation of interior insulation of outer
wall systems, and the principle of HygroWick, we have
developed a system to keep interior insulation batts dry by
using a wick that absorbs moisture from where it would
potentially condensate and transports it back to the indoor
environment. This paper describes the system including
both lab
oratory experiments and a field
test in which
prototypes of the system have been tested. Both types of
experiments are compared with two known interior
systems: Monolithic calcium silicate boards and the
system marketed as iQ-Therm [3]. For reference, the
system described here in this paper is called “HygInsu”.
The laboratory test have been described in [6], and this
work is explained in summary here in the paper.
Fig. 1
Sketch of the HygroWick system used on cold piping
(left), and the principle of the HygInsu interior wall insulation
system (right).
2 Description of HygInsu
HygInsu is a composite material consisting of an effective
insulating stone wool product protected by a diffusion-
tight vapour barrier wrapped with a moisture-transporting
fabric. Fig. 1, right, shows the composition of the
HygInsu system. When the system is installed on a wall,
the insulation plane is broken at every batt, thus creating
slits that allow the w
ick to pass through. The capillary
absorbing wick is wound around the batts in a single
continuous layer so that moisture transport will not get
interrupted. The wick is routed all the way around the
insulation batt from the side that will face the cold, solid
wall to the side that will be behind the interior wall
cladding, which will typically be gypsum board. A vapour
retarder is placed between the wick and the insulation on
the warm side of the insulation, and down the sides of the
insulation batt,
and has a
diffusion resistance
Z = 200 GPa·s·m2/kg (sd = 36 m). To prevent leaks, the
vapour retarder consists of a large rectangular piece where
the corner joints are folded in and taped.
3 Laboratory tests
3.1 Purpose
The purpose of the experiments was to compare the
efficiency of the three insulation
systems: calcium
silicate, iQ-Therm, and HygInsu when mounted as
interior insulation on a cold brick wall. The experimental
set-up was to determine the distribution of water content,
temperature, relative humidity and water vapour pressure
in the samples over time. This was done to assess whether
the samples in equilibrium were able to actively remove
moisture as it accumulated.
3.2 Method
The cold brick wall, on which the samples were placed,
was imitated by two kitchen refrigerators located in a
large climate chamber that established the indoor ambient
conditions. The drawing of an exploded view and a
picture of the front elevation of the setup are shown in Fig.
2. The refrigerator doors were replaced with sheet metal
plate, which on the outside was insulated with foam
rubber insulation. Square holes were cut in the rubber
insulation in which the interior insulation samples would
fit. Thus, the temperature difference over the samples and
the relative humidity
, RH,
in the room on the warm side
were kept constant throughout the experimental period.
The air in the climate chamber was kept constant at 23 ºC
and the humidity at 65% RH. The refrigerators were kept
a temperature of about 4 ºC, so that there would be a cold
surface with a temperature below the ambient dew point.
The samples of the three selected insulation materials
were placed in plexiglass boxes with interior dimensions
of 20 cm x 20 cm.
The boxes were made of 5 mm
plexiglass and had an inside depth of 10 cm. The boxes
allowed that the samples could easily be removed from
the cold plate for weighing at regular intervals, so changes
in total water content could be followed.
The foam rubber insulation gave a spacing of 6 cm,
between the plexiglass boxes. The foam rubber has a high
water vapour resistance factor (μ t 10,000) and good
insulation properties (
d 0.033 W/(m·K)), so the heat
flow through the samples would be practically one-
dimensional perpendicular to the insulation plane.
A fan was installed in each refrigerator to provide a
uniform temperature distribution over the cold sheet metal
plate. This, unfortunately, was not achieved as effectively
1. Fluid at below ambient
2. Cold pipe
3. HygroWick fabric
4. Mineral wool pipe section
5. Vapour retarder jacket
6. Tape for attachment
7. Evaporation area
1. Mineral wool insulation
HygroWick fabric
3. Vapour retarder
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as expected, resulting in the temperature varying from 4.5
to 7 ºC. The surface was coldest 100 cm from the ground
and warmest at the bottom. The temperature of the two
refrigerators was calibrated to be reasonably equal, but
also this was not perfectly achieved, which could have
some consequences on the comparability of the results.
Furthermore, the plexiglass boxes constituted
3-dimensional thermal bridges around the insulation
samples, which there could not be compensated for.
Fig. 2
Exploded view and picture of test setup for refrigerator
3.2.1 Samples
The two refrigerators had each their function in the
experiment. Four samples of each insulation system were
placed on the largest of the refrigerators. These 12
samples were meant to be weighed. Two other samples of
each material were put on the smallest of the refrigerators.
These 6 samples were not weighed because they were
equipped with wired moisture and temperature sensors
and should be left undisturbed during the course of the
measurements. Table 1 gives an overview of the 18
sample types and their location. The sample names are
marked in bold and will be referred to later. All samples
were constructed according to the recommendations of
the manufacturers with a material thickness of 50 mm plus
the recommended amounts of mortar and cladding.
Neither of the samples had a wall cover or surface
treatment (such as gypsum board and paint) on the surface
that faced the climate chamber. 3 Sensirion SHT75
sensors that measure temperature and humidity were used
in each of the wired samples. The sensors were placed at
depths 11, 25 and 39
mm from the front of the insulation
samples, and measurements took place at staggered
positions horizontally at the centre of each sample and
vertically at positions 50, 100 and 150 mm from the side.
Cable holes were drilled so the sensors and their cabling
did not disturb each other.
Table 1 Overview of the 18 samples and their naming.
Calc. silicate
With sensors
With sensors
With sensors
Calc. silicate
With sensors
With sensors
With sensors
Large refrigerator
Calc. silicate
Calc. silicate
Calc. silicate
Calc. silicate
As can be seen in Table 1, six of the samples are
marked as being sealed, rather than open. This means that
the moisture transport in and out the samples has been
prevented by sealing. The sealed samples were used as
references to see how the materials would behave if they
could not actively remove the moisture.
Fig. 3 A test box is wetted before start of the experiment and
edges are sealed with silicone caulking.
Upon starting the experiment, some of the samples
were wetted with water to kick-start the situation of a wet
wall and see how this moisture would move. The amount
of water added was equal to 80% of the water needed to
saturate each material. Simulations in Delphin defined the
saturation level. Thus, the calcium silicate wall samples
KA-3, KA-4 and KA-5 were wetted with 72 g of water
injected with a syringe, see Fig. 3, left. 50 g was added to
Metal plate
Rubber insulation
Plexiglass box
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the iQ-Therm wall samples IQ-3, IQ-4, IQ-5 and IQ-6,
and 10 g was added to the HygInsu wall samples HY-3,
HY-4 and HY-5. The duration of the measuring period
was 116 days.
3.3 Result and Analysis
3.3.1 Weighing results
Fig. 4 shows all the weighing
results for the three materials. Each curve refers to one of
the samples described in Table 1. The data points
illustrated with squares (■) are for calcium silicate, where
open samples are red. Diamonds (♦) indicate the iQ-
Therm results, and all the open samples are green. The
results of the HygInsu samples are illustrated with circles
(●) and the open samples have blue colours. Sealed
samples are all black, no matter the insulation type. The
weight gain is the difference between the measured
weight and the initial weight.
Calcium silicate
As shown in Fig. 4, the sealed calcium
silicate sample does not gain weight at all because of its
diffusion-tight paint. However, the open samples quickly
gain weight, and after 10 weeks there is a maximum
increase of 97 grams. After this peak, the weight change
becomes more subtle, indicating that an equilibrium with
the humidity of the ambient climate chamber has been
attained. Common for all the initially soaked samples is
that they lose much of the liquid added at the start of the
The first thing to note when considering the weighing
results for iQ-Therm in Fig. 4 is that the weight gain is
much lower than that of calcium silicate. This is caused
by the calcium silicate being very hydrophilic, while
polyurethane core of iQ-Therm is water resistant with a
closed pore system, meaning that the water is located
primarily in the adhesive mortar near the cold surface. The
graphs also show that all four samples have had the same
constant weight gain since week 2 without signs of
change. The last measurement is therefore also the
highest, which means that there is no indication that the
iQ-Therm tests have come in equilibrium with the indoor
Due to the diffusion-tight vapour barrier that closes
tightly around the mineral wool, the samples
not gain
much in weight. For this reason, it would take long time
before the wick would become wet enough to make the
liquid transporting properties of HygInsu influential. To
determine whether the HygInsu samples have a liquid
moisture transporting property, the samples HY-5 and
HY-4 were therefore wetted with some extra 20 grams of
liquid during the experimental period. The water was
supplied by means of a thin syringe and the hole in the
vapour barrier subsequently sealed with tape. The 20
grams of water was supplied at
a depth of 2.5 cm in the
middle of the sample, but as shown in Fig. 4,
it was removed with approximately one month when it got
in contact with the HygroWick. By capillary action, the
wick has led the moisture to the warm surface of the
assembly from where it could evaporate towards the
climate chamber. The result shows that HygInsu has an
effective property for draining, which means that the
assembly quickly attains a dry situation.
Measurements from sensors
Measurements were taken over a period of 112 days.
For each material type, a first graph presents the
development over time. The subsequent two smaller
graphs show the moisture distributions within the samples
at the end of the experimental period for the open and
sealed experiments, respectively.
Calcium silicate
The measurements for KA-1 (11 mm) show that the
relative humidity decreases during the first few weeks,
while measurements for KA-1 (39 mm) increase. This
shows that moisture accumulates where it is coldest and
the water evaporates from the free surface to the ambient
chamber. The results of the middle sensor in the
open sample KA-1 (25 mm) show that after it has dropped
in the first few days, it begins to rise and after two months
it is at the same level like the rear sensor. This means that
the condensation on the cold side has gradually spread
further towards the warm side until it finally reached the
sensor in the centre of the sample. The striking increase in
relative humidity also corresponds to the large weight
gain, which was seen in Fig. 4.
measurements for the seal
ed sample KA-2 show
almost as high relative humidity as the open. The reason
could be due to water that has penetrated through the
drilled holes in the side of the sample through which the
sensor wires were led.
The open iQ-Therm sample (IQ-1) becomes more
water filled than the sealed (IQ-2), especially in the two
measuring points closest to the cold surface. This can be
seen in Fig. 6 where the points for the relative humidity
graph at a distance of 2.5 cm and 3.9 cm from the inner
surface as well is higher.
The graph of the vapour pressure for IQ-1 makes an
unnatural kink in Fig. 6, lower left. This is because of the
low values in relative humidity measured in IQ-1 (11
mm). Since the sensors only measure relative humidity
and temperature, the vapour pressure is determined from
p =
·ps. The relative humidity at this point may be a
result of the position of a sensor
to the capillary
active channels.
There is a clear linear correspondence between the
relative humidity and all of the three points in the mineral
wool. This linearity is due to the fact that the material is
homogeneous and unlike the other materials, the mineral
wool has no capillary active or moisture absorbing
properties. Therefore, there is no gradient in vapour
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pressure, and almost no change over time and no fluid
front. Naturally, the relative humidity is highest near the
cold surface.
The sealed sample should contain more moisture as it
has no possibility to actively drain it, but this is not
immediately apparent from these results. A probable
reason could be that the liquid will be localized in a thin
layer at the cold surface rather than within the mineral
wool, and thus will not influence even the coldest sensor.
Fig. 4 Results from weighing of all samples from the large refrigerator.
4 Field test
4.1 Description of the set-up
A field test of a full-scale wall with HygInsu as
interior insulation was carried out in an outdoor field test
site of the Technical University of Denmark, 15 km north
of Copenhagen city centre. The facility was comprised of
two 40“ reefer containers that were positioned on the test
site such that one of the long-sided wall surfaces faced
north-east (and the opposite side faced south-west), and
1 m wide x 2 m tall openings were cut in the insulated
steel walls in which some solid 1½ stone (34.8 cm) walls
Weight gain, g
Date [dd/mm]
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were bricked up. Each façade made room for 8 such wall
mock-ups. See the exterior set-up on Fig. 8.
Fig. 5 Sensor results of the evolution and distribution of
moisture content in calcium silicate. The lower graphs show
moisture distributions after 112 days with relative humidity
(·····), vapour pressure (───), and saturation vapour pressure
Lower graphs are for the open specimen on the left and
sealed specimen on the right.
Fig. 6. Sensor results of the evolution and distribution of
moisture content in iQ-Therm. Horizontal gray and red lines
merely symbolize the calciumsilicate channels that pentrate the
material, and are not to be seen as indicators of particular
humidity values. Significance of line types like in Fig. 5.
Fig. 7. Sensor results of the evolution and distribution of
moisture content in HygInsu. Significance of line types like in
Fig. 5.
Fig. 8. South-west façade of reefer container used as facility
for tests of hygrothermal conditions in interior insulated
masonry walls.
Fig. 9. Vertical cross-section of wall with interior insulation
and location of sensors. Measuring positions 8 and 9 are
duplicates of positions 3 and 4, but are placed at the separation
wall, which can be seen on the right-hand side of the photo.
The photo shows the wall with iQ-Therm insulation in place
before mounting the interior gypsum wall cladding.
The masonry was covered on the inside with 10 mm
lime render. Around mid-height of each wall mock-up
was positioned a wooden beam of 17.5x17.5 cm cross
section, which extended about half a meter into the room
of the container and 10 cm into the masonry. The beam
rested on a horizontal, longitudinal 10x10 cm wooden
lath, which was inserted in a recess in the masonry. A
15 mm OSB
board over
and under the part of the beam
that stretched into the room mimicked floor and ceiling in
a floor separation, and it was partly filled with a 100 mm
mineral wool batt. An indoor separation wall of half stone
brick (10.8 cm plus 10 mm lime render on either side) was
Relative humidity [%]
Relative humidity [%]
Relative humidity [%]
Relative humidity [%]
Relative humidity [%]
Relative humidity [%]
Relative humidity [%]
Relative humidity [%]
Vapour pressure [Pa]
Vapour pressure [Pa]
Vapour pressure [Pa]
Vapour pressure [Pa]
Vapour pressure [Pa]
Vapour pressure [Pa]
Distance from warm surface [cm]
Distance from warm surface [cm]
Distance from warm surface [cm]
Distance from warm surface [cm]
Distance from warm surface [cm]
Distance from warm surface [cm]
Relative humidity [%]
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positioned in full wall height next to the wooden beam,
see the picture in Fig. 9 (right). 2 x 12 mm gypsum board
was used as interior cladding of the insulation. No vapour
retarder or interior paint was used in the walls described
in this paper. Each wall was instrumented with 9
HYT 221 sensors (from Innovative Sensor Technology,
IST AG) that measured temperature and relative humidity
with hourly intervals in two positions in the masonry, in
the lime render, on the warm side of
the insulation, at two
positions in the wooden beam, and on the cold side of the
wooden lath. A weather station measured the outdoor
weather conditions and indoor temperature and relative
humidity was logged with hourly intervals. A vertical
cross-section through the set-up with indication of sensor
positions is shown in Fig. 9 (left). Further description of
the facility, its measuring system, and the other walls can
be found in the PhD-thesis of Tommy Odgaard [2].
A wall, which was insulated on the interior side with
the HygInsu system (of thickness 100
mm) occupied one
of the places facing north-east. The instrumented wall
cavity that was insulated with the HygInsu system was
positioned over beam height and had width 530 mm and
height 952 mm. The HygInsu sample fit tight to the sides
of the cavity.
Along the same façade were also two walls, which
were insulated with calcium silicate (100 mm) and iQ-
Therm (80 mm), respectively. The iQ-Therm and calcium
silicate insulation systems used a dedicated glue mortar to
adhere th
e insulation to the lime render, and these two
walls did not have gypsum boards as interior cladding.
Fig. 10. Left: Insulation batt with HygInsu system before
installation. Right: Place reserved for HygInsu system behind
interior rendering of the masonry with sensors to measure
humidity at the wick/render interface.
4.2 Experimental conditions
The interior of the container was heated with electric
heaters to around 20°C, and a humidifier kept the
humidity at the relatively high level of around 60% RH
year round (although the humidifier was off for a few
months in the winter 2018/19). Fans stirred the air so the
interior conditions were well mixed. A picture of the
containers with their masonry wall is shown in Fig. 8. The
interior insulation system with HygInsu was mounted in
November 2016, whereas the walls with calcium silicate
and iQ-Therm had been installed and in operation since
May 2015. Fig. 10 shows a picture of an insulation batt of
stone wool outfitted with the HygInsu system. In addition
to the HYT sensor, which measures temperature and RH
within the wall rendering, three HYT sensors in different
lateral and vertical positions close to the centre and
perimeter of the insulation batt measured temperature and
RH at the interface between the HygInsu system’s
Hygrowick glass fibre felt at the cold, outer side of the
insulation. Like in other walls, a HYT sensor measured
temperature and RH in the interface between interior
gypsum cladding and the insulation system close to the
centre of the insulation.
4.3 Results
The results are illustrated by means of the measured
relative humidity in some of the positions, which are
deemed to be most interesting and also most likely
influenced by the performance of the insulation system.
These are:
xMeasuring position 3, in lime render on the inside of
the masonry/outs
ide of
the insulation system and its glue
mortar. Three extra measurement positions for HygInsu at
the interface between wick and render (Fig. 11).
xMeasuring position 4, in interface between interior
gypsum cladding and inside surface of insulation (Fig. 12)
xMeasuring position 5, at the cold, exterior side of the
wooden lath (Fig. 13)
xMeasuring position 6, in wooden beam end (Fig. 14).
Fig. 11. Relative humidity in lime render on the inside of the
masonry, and for HygInsu in the positions of the wick/render
interface (measuring position 3).
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Fig. 12. Relative humidity in the indoor environment,
and at interface between interior cladding and inside
surface of insulation (measuring position 4).
Fig. 13. Relative humidity at cold, exterior side of wooden lath
(measuring position 5).
Fig. 14. Relative humidity in wooden beam end (measuring
position 6).
5 Discussion and Conclusion
The paper has demonstrated some initial experiments of
laboratory and outdoor
test performance of
prototypes of a new thermal insulation composite, named
HygInsu, which is comprised of mineral wool convoluted
in a capillary active fabric of glass fibre felt. The capillary
active glass fibre felt makes it possible to remove the high
moisture content that may usually occur in the critical
interface between insulation and the inside of a solid brick
wall. The new system has been tested side by side with
commercial products of calcium silicate and a
polyurethane product with capillary active calcium
silicate channels (iQ-Therm). The experiments have
, both in the laboratory tests that lasted almost four
months and in the three-year field study, that the commer-
cial systems may have critically high moisture levels.
In the case of laboratory tests with calcium silicate, the
moisture content was steadily increasing for a couple of
months and then reached a situation with steady high
moisture content. Relative humidity reached saturation
(100% RH) for the coldest half of the material.
iQ-Therm performed better in the laboratory tests with
only slow changes of moisture content and relative
humidity, and tendencies that could go both up and down
in moisture content
during the measurement period
. RH
was around 90 % on the cold side.
HygInsu demonstrated a very good capability in the
laboratory tests to drain surplus moisture from the
assembly, and the relative humidity measured in the
material tended to be a little lower than what was
measured for iQ-Therm, with RH topping at around 85%
among the measured positions. The system demonstrated
at two occasions in the laboratory test that it was able
within a month to drain surplus moisture that was added
to the assembly. Thus, the system may have some
resiliency to dry out moisture that in a practical situation
has inadvertently entered the construction.
In the field tests
, only relative humidity was measured
as an indicator for moisture, but this was done in several
positions in the tested brick walls with interior insulation.
At the render on the cold side of the insulation system, the
relative humidity was critically high for calcium silicate
and iQ-Therm with values mostly above 90% or at
saturation for calcium silicate, and around or above 90 %
for iQ-Therm. Among the wooden members, the wooden
had critical relative humidity with the iQ
system as RH was mostly above 90%. The beam end
performed better with RH around 80% or lower.
With calcium silicate, both the wooden lath and the
beam end had RH mostly between 80 and 90 %, which
can be assessed as a high, but perhaps not critical level.
A short summary of the humidity conditions seen in
the field test with the HygInsu system is that the humidity
was mostly at the same or slightly lower levels than what
was seen in walls with the two other insulation systems.
Particularly at the render outside of the insulation, there
was a tendency for the relative humidity to be some 10%
RH lower with HygInsu than with the two other systems.
A future study should use the measured data together
with a recognized mould growth model to analyse the risk
of fungal activity on the measured positions.
Altogether, while it has been sad to see some rather
high humidity values in many of the performed tests, it
has been encouraging to see the equal or somewhat better
performance of the new insulation principle with
HygInsu. However, it must be stated that these have been
only some first tests of prototypical examples of the
system, and more testing and assessment shall be needed.
1. RIBuild, Robust Internal Thermal Insulation of
Historic Buildings,
2. T. Odgaard, Challenges when retrofitting multi-storey
buildings consisting of solid masonry facades and
embedded wood with interior thermal insulation. PhD
thesis, Technical University of Denmark (2019)
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Full-text available
Today, approximately 25 % of the apartments in the Danish multi-storey stock of more than two stories are found in buildings with masonry facades erected in the period 1850-1930. Of these apartments, 71 % are situated in Copenhagen, the Danish capital. The building traditions and norms in force during the period entail that these buildings share similar characteristics, including solid masonry walls and embedded wooden components. The energy use and indoor climate was not in focus during construction, wherefore the current occupants cannot expect modern levels of thermal comfort and the section include a considerable energy saving potential. It is evident that thermal comfort and energy use can be improved by increasing the thermal resistance of the façade. With focus on the masonry part of the total façade area, this can be achieved with thermal insulation applied to the interior or exterior surface. While application to the exterior surface is the best solution from a building physics point of view, the retention of the exterior façade expression is often a desire from the owner or a preservation requirement, leaving application to the interior surface as the only possibility. The buildings from the period have been investigated to determine the degree of shared characteristics within the building segment, showing similar building techniques with consistent thin spandrels under the windows and a low share of available interior surface area for the application of insulation. There were performed thermal simulations of characteristic façade sections in 3-dimensional models, finding that insulation of the spandrel can achieve up to 40 % of the maximum possible reduction achievable from reducing the thermal transmittance by retrofitting the masonry with interior insulation. The influence on the hygrothermal conditions when applying interior thermal insulation to solid masonry walls have been investigated experimentally in a case study and by comparative analyses of results from two field experiments. The case study was 2 rooms in a dormitory with a normal indoor moisture load, situated at an urban location. The study showed how retrofitting the interior surface of a solid masonry spandrel with a diffusion open thermal insulation system changed the hygrothermal balance in the wall, resulting in a colder and wetter wall with similar conditions throughout the wall. Evaluation of the case study, based on measurements and on-site investigations, showed no calculated or observed risks of moisture-induced damage. The field experiments were designed and constructed with an extensive measurement program, exposed to a high indoor moisture load and located in a rural area. The measurements were used for comparative analyses, to investigate the difference in hygrothermal performance of different interior thermal insulation systems, applied to the entire masonry surface or with some variations within the systems. The comparative analyses were based on the measured relative humidity, temperature and on mathematical damage models able to take exposure time into consideration. The damage models were used to compare the calculated risks of moisture-induced damage in the different systems. The results of the comparative analyses with the boundary conditions of the field experiments showed: * Application of a thermal insulation system depending on a tight vapour barrier or a diffusion open thermal insulation system resulted in an increase in calculated mould germination and growth on the masonry surface behind the insulation. * Application of a thermal insulation system depending on a tight vapour barrier resulted in an increase in calculated irreversible wooden decay in the wooden beam (floor joist), compared to other insulation systems and an un-insulated wall. * Hydrophobizing the exterior masonry surface with a hydrophobic façade treatment had an overall positive effect on the hygrothermal conditions, and can be further improved by replacing a part of the moisture-open insulation with autoclaved aerated concrete.
The wick-concept for thermal insulation of cold piping is based on capillary suction of a fiber fabric to remove excess water from the pipe surface by transporting it to the outer surface of the insulation. From the surface of the insulation jacket, the water will evaporate to the ambient air. This will prevent long-term accumulation of moisture in the insulation material. The wick keeps the hydrophobic insulation dry, allowing it to maintain its thermal performance. The liquid moisture is kept only in the wick fabric. This article presents the principle of operation of cold pipe insulation using the wick-concept in either of two variations: the self-drying or the self-sealing system. Experiments have been carried out using different variations of the two systems to investigate the conditions for exploiting the drying capabilities of the systems, and the results are presented. The results show that the variations of these types of insulation systems work for pipes with a temperature above 0 C and for ambient conditions within common ranges for industrial applications.
Environmental impact and moisture transporting properties of materials used as internal extra insulation
  • N K Friis
  • C Pedersen
Robust Internal Thermal Insulation of Historic Buildings
  • Ribuild
RIBuild, Robust Internal Thermal Insulation of Historic Buildings, (2020)