Effect of method, step size and drying temperature on sorption ...

<strong>Effect</strong> <strong>of</strong> <strong>method</strong>, <strong>step</strong> <strong>size</strong> <strong>and</strong> <strong>drying</strong> <strong>temperature</strong> on
sorption isotherms
Ruut Peuhkuri, Assistant Pr<strong>of</strong>essor,
rhp@byg.dtu.dk
Carsten Rode, Associate Pr<strong>of</strong>essor,
car@byg.dtu.dk
Kurt Kielsgaard Hansen, Associate Pr<strong>of</strong>essor,
kkh@byg.dtu.dk
Department <strong>of</strong> Civil Engineering, Technical University <strong>of</strong> Denmark
http://www.byg.dtu.dk
KEYWORDS: sorption isotherm, hygroscopic, measurement <strong>method</strong>s, <strong>drying</strong> <strong>temperature</strong>.
SUMMARY:
One <strong>of</strong> the most important hygrothermal material properties is the sorption curve, which gives the
equilibrium moisture content <strong>of</strong> the material for relative humidity from 0 to 98 %. Some studies have shown
that the resulting sorption curves vary surprisingly widely, even though the <strong>method</strong> <strong>and</strong> especially the
materials are the same.
The determination <strong>of</strong> the sorption curve has traditionally been a very lengthy <strong>and</strong> laborious process.
Therefore there is an increasing interest in developing <strong>and</strong> using time saving <strong>method</strong>s for sorption
measurements. These could be using fewer measurement points <strong>and</strong>/or increasing <strong>drying</strong> <strong>temperature</strong>s.
When reducing the time used for tests the risk <strong>of</strong> not reaching the equilibrium <strong>and</strong> by that the true
equilibrium moisture content will increase. A sufficient compromise between the accuracy <strong>and</strong> the
time/labour savings should possibly be found.
In this paper some aspects supposed to have impact on the resulting sorption curve – choice <strong>of</strong> <strong>method</strong>,
<strong>step</strong> <strong>size</strong> <strong>and</strong> <strong>drying</strong> <strong>temperature</strong> – will be analysed by comparing the resulting sorption curves with each
other <strong>and</strong> discussing uncertainties, pros <strong>and</strong> cons. The investigated materials are various building
materials, including a range <strong>of</strong> insulation materials.
1. Introduction
The quality <strong>of</strong> the prediction <strong>of</strong> the hygrothermal performance <strong>of</strong> building materials <strong>and</strong> constructions is
highly dependent on the used material data in the simulations. One <strong>of</strong> the most important material
properties is the sorption curve, which gives the equilibrium moisture content <strong>of</strong> the material through out
the relative humidity (RH) range. Distinction is usually made between wetting – adsorption, <strong>and</strong> <strong>drying</strong> –
desorption.
According to EN ISO 12571 Determination <strong>of</strong> hygroscopic sorption properties (ISO 2000) there are two
st<strong>and</strong>ard <strong>method</strong>s for determining the sorption curve: 1) Desiccator <strong>method</strong>, where the RH in desiccators is
maintained by the saturated salt solutions <strong>and</strong> 2) Climatic chamber <strong>method</strong>, where the <strong>temperature</strong> (T) <strong>and</strong>
RH <strong>of</strong> the air in the chamber are controlled. The <strong>temperature</strong> is maintained constant during the
measurements, 23ºC, therefore the resulting curve is also called the sorption isotherm. The st<strong>and</strong>ard test
procedure is to dry the samples in the beginning (gives the dry mass m0) <strong>and</strong> then place the samples
consecutively in series, where RH is increasing in stages. After equilibrium is reached at a given RH, the
moist mass (m) can be determined. The moisture content by mass u [kg/kg] for the given RH can be
determined from

u
m − m
m
0 = (1)
0
These moisture contents for increasing RH together govern the absorption curve that describes the wetting.
In the same way, the desorption curve can be determined describing <strong>drying</strong>, but now the starting point is a
moist sample (>95 %RH) <strong>and</strong> the RH will be decreasing. The st<strong>and</strong>ard gives also guidelines for sample
<strong>size</strong>, number <strong>of</strong> samples <strong>and</strong> equilibrium criteria.
Some studies have shown that measured sorption curves can vary surprisingly widely, even though the
<strong>method</strong> <strong>and</strong> the materials have been the same (Wilkes et al, 2004). Different traditions for experimental
work <strong>and</strong> different laboratory equipment may be the explanation. However, using the st<strong>and</strong>ardized <strong>method</strong>,
one should always get the same measurement result within the accuracy <strong>of</strong> the equipment.
For practical design purposes, usually catalogue material properties are used, as they present some kind <strong>of</strong>
average for a product type, <strong>and</strong> the design process takes place before any materials are chosen for the
constructions. For research purposes, in contrary, minimising any possibility <strong>of</strong> error will have impact on
the final result. Therefore, the material properties <strong>of</strong> the samples used in any experimental work have to be
determined, if the results are going to be compared with a theoretical model with numerical simulations.
Determination <strong>of</strong> the sorption curve has traditionally been a very lengthy <strong>and</strong> laborious process. Therefore
there is an increasing interest in developing <strong>and</strong> using rapid <strong>method</strong>s for sorption measurements (Janz,
2000; Johannesson, 2000; Kelly, 2002). When reducing the time used for tests the risk <strong>of</strong> not reaching the
equilibrium <strong>and</strong> by that the true equilibrium moisture content will increase. A sufficient compromise
between the accuracy <strong>and</strong> the time/labour savings should be possible to be found.
In this paper several aspects supposed to have impact on the resulting sorption curve will be analysed by
comparing the resulting sorption curves with each other <strong>and</strong> discussing uncertainties <strong>and</strong> pros <strong>and</strong> cons.
The measurement data has been produced by the Authors <strong>and</strong>/or by their staff members.
The scope <strong>of</strong> this work was to investigate
• If the st<strong>and</strong>ard <strong>and</strong> rapid sorption <strong>method</strong>s will result in the same sorption curve.
• If the <strong>step</strong> <strong>size</strong> has a significant effect on the equilibrium moisture content.
• If the <strong>drying</strong> <strong>temperature</strong> level has a significant effect on the equilibrium moisture content.
• If the <strong>drying</strong> <strong>of</strong> a sample at elevated <strong>temperature</strong>s alters the hygroscopic behaviour <strong>of</strong> the material.
2. Experiments
The experimental work presented in this paper has been going in the period 1999-2004. The complete
description <strong>of</strong> all the experimental set-ups can be found in the referred works.
2.1 Materials <strong>and</strong> sample <strong>size</strong>s
Table 1 introduces the materials used in these moisture sorption experiments. Also sample weights are
given to illustrate the <strong>size</strong> <strong>of</strong> the used samples. There were used 2-6 duplicates in the climatic chamber
tests <strong>and</strong> only one sample for IGAsorp tests. The latter choice was due to the experiences by (Kelly, 2002),
where the duplicates did not add to the reliability <strong>of</strong> the results.
TABLE 1: The materials used for sorption measurements with the dry density <strong>and</strong> approximate mean
sample weights .
Material Dry density Approximate sample weight
[kg/m³] Climatic chamber [g] IGAsorp [mg]
Flax insulation 30 12 45
Perlite insulation 35 47 50
Cellulose insulation 65 20 62
Glass wool insulation 75 25 54
Cellular concrete 450 15 113

2.2 Experimental <strong>method</strong>s
The sorption curves to be presented in this paper have been determinated by using two different <strong>method</strong>s
<strong>and</strong> corresponding laboratory equipments <strong>and</strong> set-ups:
1. IGAsorp apparatus (rapid <strong>method</strong>)
2. Climatic chamber <strong>method</strong> (st<strong>and</strong>ard <strong>method</strong>)
Additionally, the effect <strong>of</strong> the <strong>step</strong> <strong>size</strong> on the resulting sorption curve has been investigated with the
IGAsorp equipment. The effect <strong>of</strong> the <strong>drying</strong> <strong>temperature</strong> has been analysed with both <strong>method</strong>s. These setups
are briefly described in the following.
(a) (b)
FIG. 1: (a) The st<strong>and</strong>ard sorption equipment (IGAsorp) <strong>and</strong> (b) the climatic chamber.
2.2.1 IGAsorp apparatus – rapid <strong>method</strong>
The IGAsorp (see Fig. 1 (a)) is a st<strong>and</strong>ard sorption equipment, which has a sensitive microbalance
(resolution 1µg <strong>and</strong> capacity 200 mg), which continuously registers the weight <strong>of</strong> the sample together with
the <strong>temperature</strong> <strong>and</strong> relative humidity around the sample. The <strong>temperature</strong> can be varied from 5 ºC to 80 ºC
<strong>and</strong> the relative humidity from 0 % RH to 95 % RH with an accuracy <strong>of</strong> ± 1% for 0 - 90%RH <strong>and</strong> ± 2% for
90 - 95%RH. The sample is placed within a weighing basket <strong>and</strong> positioned on the microbalance. The
chamber is then closed <strong>and</strong> the sample sealed in position. Drying <strong>of</strong> the sample before sorption
measurements is carried out at 20 ºC in flowing nitrogen until the weight <strong>of</strong> the sample is in equilibrium at
RH

Elevated <strong>drying</strong> <strong>temperature</strong>s
The test procedure for investigation <strong>of</strong> the effect <strong>of</strong> the <strong>drying</strong> at elevated <strong>temperature</strong>s on the resulting
sorption curve <strong>and</strong> the hygroscopic behaviour <strong>of</strong> the material was to dry the sample immediately after the
determination <strong>of</strong> the sorption curve at 50ºC <strong>and</strong> 70ºC, which in both cases takes appr. 12h to reach
equilibrium weight. The second sorption isotherm was then measured immediately after the <strong>drying</strong>, again
without opening the chamber. In this way, the errors when h<strong>and</strong>ling the sample were minimised.
2.2.2 Climatic chambers – st<strong>and</strong>ard <strong>method</strong>
During the measurements, the samples were placed in net bags – made <strong>of</strong> a practically moisture inert
polyester to ensure no loss <strong>of</strong> material –<strong>and</strong> positioned in a climatic chamber, which is a redesigned kitchen
refrigerator. The climate is automatically controlled <strong>and</strong> maintains the desired <strong>temperature</strong> (20 ± 0,4 ºC)
<strong>and</strong> relative humidity with the given accuracy: ± 0,2 (low RH) - 2,0 (high RH) % RH. The RH can be
varied in the range 2 – 96 %RH. The net bags are moved in turns to a hook attached to a balance for
weighing without opening the chamber. The resolution <strong>of</strong> the balance is 0.001g .The relative humidity is
altered in <strong>step</strong>s after the samples have reached the equilibrium. The design <strong>of</strong> the equipment is described in
detail in (Strømdahl 2000).
The insulation materials flax, perlite <strong>and</strong> cellulose fibres were measured with 10 %RH <strong>step</strong>s for absorption.
But for low (3 – 15 %) <strong>and</strong> high end (90 – 96%) RHs, the <strong>step</strong>s were 2 – 3 %RH to get a more detailed
picture <strong>of</strong> these areas (Hansen et al, 1999b). The materials cellular concrete <strong>and</strong> glass wool were also
measured with 10 %RH <strong>step</strong>s for the most <strong>of</strong> the RH-range, but less attention was paid to low RHs. The
high end (85 – 95%) was measured with 5% <strong>step</strong>s. The desorption isotherm was in all cases measured with
fewer points. The final <strong>drying</strong> took place outside the chamber: at 20ºC over magnesium perchlorate giving
< 1 %RH in a desiccator. The elevated <strong>temperature</strong>s were reached in an oven.
3. Results
The results are given as sorption curves at 20 ºC, where moisture content by mass u [kg/kg] is given as a
function <strong>of</strong> RH [-]. For many cases, only the absorption isotherm is shown for the clarity <strong>of</strong> the diagrams.
3.1 <strong>Effect</strong> <strong>of</strong> <strong>method</strong>
Fig. 2 gives an overview <strong>of</strong> all the main sorption curves found, where the <strong>drying</strong> for determination <strong>of</strong> m0
took place at 20 ºC <strong>and</strong> < 1 %RH. For IGAsorp, 5 %RH <strong>step</strong>s were used. Results for both <strong>method</strong>s, the
rapid <strong>method</strong> using IGAsorp apparatus <strong>and</strong> the st<strong>and</strong>ard <strong>method</strong> using climatic chamber are shown in the
same diagram. Negative values for perlite are simply due to that the weight <strong>of</strong> the sample decreased in the
beginning <strong>of</strong> absorption process.
3.2 <strong>Effect</strong> <strong>of</strong> <strong>step</strong> <strong>size</strong>
The effect <strong>of</strong> the <strong>step</strong> <strong>size</strong> used during the measurements on the resulting sorption curves was investigated
for all the materials but perlite. For these measurements only the IGAsorp apparatus was used. The sorption
curves found are shown in Fig. 3. Steps <strong>of</strong> 5 %, 10 % <strong>and</strong> 20 %RH were used.
3.3 <strong>Effect</strong> <strong>of</strong> <strong>drying</strong> <strong>temperature</strong>
The effect <strong>of</strong> <strong>drying</strong> <strong>temperature</strong> on the resulting sorption curve was investigated for all materials with both
<strong>method</strong>s. The determined absorption curves are shown in Fig 4 only for cellulose <strong>and</strong> glass wool. Also flax
<strong>and</strong> perlite showed similar behaviour as cellulose, where the equilibrium moisture content increases for
increasing <strong>drying</strong> <strong>temperature</strong>. Only glass wool did not show any effect <strong>of</strong> <strong>drying</strong> <strong>temperature</strong>.
3.4 <strong>Effect</strong> <strong>of</strong> <strong>drying</strong> <strong>temperature</strong> on the hygroscopic behaviour
Finally, Fig 5 shows 2 sets <strong>of</strong> absorption curves for cellulose <strong>and</strong> cellular concrete determined with the
rapid <strong>method</strong>. The first isotherm was measured after the sample had been dried at 20ºC <strong>and</strong> the second one
after <strong>drying</strong> in 70ºC. Also perlite <strong>and</strong> glass wool have a similar behaviour as cellulose.

Moisture content [kg/kg]
Moisture content [kg/kg]
Moisture content [kg/kg]
0.500
0.450
0.400
0.350
0.300
0.250
0.200
0.150
0.100
0.050
0.000
0.500
0.450
0.400
0.350
0.300
0.250
0.200
0.150
0.100
0.050
0.000
0.060
0.050
0.040
0.030
0.020
0.010
0.000
Flax
Absorption Igasorp
Desorption Igasorp
Absorption Climatic Chamber
Desorption Climatic Chamber
0.0 0.2 0.4 0.6 0.8 1.0
Relative humidity [-]
Cellulose
Absorption Igasorp
Desorption Igasorp
Absorption Climatic Chamber
Desorption Climatic Chamber
0.0 0.2 0.4 0.6 0.8 1.0
Relative humidity [-]
Aerated cellular concrete
Absorption Igasorp
Desorption Igasorp
Absorption Climatic Chamber
Desorption Climatic Chamber
0.0 0.2 0.4 0.6 0.8 1.0
Relative humidity [-]
Moisture content [kg/kg]
Moisture content [kg/kg]
0.020
0.018
0.016
0.014
0.012
0.010
0.008
0.006
0.004
0.002
Perlite
Absorption Igasorp
Desorption Igasorp
Absorption Climatic Chamber
Desorption Climatic Chamber
0.000
0.0
-0.002
0.2 0.4 0.6 0.8 1.0
Relative humidity [-]
0.060
0.050
0.040
0.030
0.020
0.010
0.000
Glass wool
Absorption Igasorp
Desorption Igasorp
Absorption Climatic Chamber
Desorption Climatic Chamber
0.0 0.2 0.4 0.6 0.8 1.0
Relative humidity [-]
FIG. 2: Sorption curves at 20 ºC . Comparison <strong>of</strong> st<strong>and</strong>ard <strong>method</strong> using climatic chamber <strong>and</strong> rapid
<strong>method</strong> using IGAsorp apparatus.

Moisture content [kg/kg]
Moisture content [kg/kg]
0.300
0.250
0.200
0.150
0.100
0.050
0.000
0.050
0.045
0.040
0.035
0.030
0.025
0.020
0.015
0.010
0.005
0.000
5 % RH <strong>step</strong>s
10 % RH <strong>step</strong>s
20 % RH <strong>step</strong>s
Flax
0.0 0.2 0.4 0.6 0.8 1.0
Relative humidity [-]
5 % RH <strong>step</strong>s
10 % RH <strong>step</strong>s
20 % RH <strong>step</strong>s
Glass wool
0.0 0.2 0.4 0.6 0.8 1.0
Relative humidity [-]
Moisture content [kg/kg]
Moisture content [kg/kg]
0.300
0.250
0.200
0.150
0.100
0.050
0.000
0.060
0.050
0.040
0.030
0.020
0.010
0.000
5 % RH <strong>step</strong>s
10 % RH <strong>step</strong>s
20 % RH <strong>step</strong>s
Cellulose
0.0 0.2 0.4 0.6 0.8 1.0
Relative humidity [-]
5 % RH <strong>step</strong>s
Cellular concrete
10 % RH <strong>step</strong>s
20 % RH <strong>step</strong>s
0.0 0.2 0.4 0.6 0.8 1.0
Relative humidity [-]
FIG. 3: Sorption curves at 20 ºC that show the effect <strong>of</strong> the <strong>step</strong> <strong>size</strong> used for the measurements.Measured
using IGAsorp apparatus.
4. Discussion
When comparing the two <strong>method</strong>s used, it is clear that the sorption curves found are close to identical for
most <strong>of</strong> the materials. Some strange results were also achieved: absorption curve for flax using the st<strong>and</strong>ard
<strong>method</strong> was higher than desorption curve. The most likely explanation is the leaching out <strong>of</strong> the added salts
(fire retarders) at high RH's <strong>and</strong> following loss <strong>of</strong> weight as a result <strong>of</strong> the manual h<strong>and</strong>ling <strong>of</strong> the samples.
These salts are extremely hygroscopic (Hansen et.al, 1999a), <strong>and</strong> a loss <strong>of</strong> these salts gives a reduced
moisture content compared to absorption. This is also slightly seen for cellulose. On the other h<strong>and</strong>, the
desorption curve for cellular concrete using st<strong>and</strong>ard <strong>method</strong> tends to be too high, most likely due to too
thick samples (10 mm) compared to time used for reaching equilibrium.
The <strong>size</strong> <strong>of</strong> the <strong>step</strong>s used during the measurements did not have any particular effect on the resulting
sorption curve. However, the <strong>size</strong> <strong>of</strong> hysteresis effect seemed to be reduced for increasing <strong>step</strong> <strong>size</strong>. The
benefit <strong>of</strong> using many relative humidity levels is, however, that the resulting curve will be more smooth.
On the other h<strong>and</strong>, using just a few relative humidity levels can reduce the measurement time significantly.
The <strong>drying</strong> <strong>temperature</strong> does have a significant effect on the determined sorption curves. A question
connected to this is: When can the sample be seen to be dry? Traditionally a <strong>drying</strong> <strong>temperature</strong> <strong>of</strong> 105ºC
has been used, because at this <strong>temperature</strong> all the physically bound water is removed. However, not all the

Moisture content [kg/kg]
0.500
0.450
0.400
0.350
0.300
0.250
0.200
0.150
0.100
0.050
0.000
Cellulose (absorption)
T=20ºC (CC)
T=70ºC (CC)
T=105ºC (CC)
T=20ºC (IS)
T=50ºC (IS)
T=70ºC (IS)
0.0 0.2 0.4 0.6 0.8 1.0
Relative humidity [-]
Moisture content [kg/kg]
0.060
0.050
0.040
0.030
0.020
0.010
0.000
Glass wool (absorption)
T=20ºC (CC) initial m0
T=20ºC (CC)
T=50ºC (CC)
T=70ºC (CC)
T=20ºC (IS)
T=50ºC (IS)
T=70ºC (IS)
0.0 0.2 0.4 0.6 0.8 1.0
Relative humidity [-]
FIG. 4: Absorption curves at 20 ºC for cellulose <strong>and</strong> glass wool that show the effect <strong>of</strong> the different <strong>drying</strong>
<strong>temperature</strong> on the equilibrium moisture content. Note that the <strong>drying</strong> <strong>temperature</strong>s shown in diagrams are
not identical in both cases.(IS = IGAsorp <strong>and</strong> CC = climatic chamber)
Moisture content [kg/kg]
0.300
0.250
0.200
0.150
0.100
0.050
0.000
Cellulose (absorption)
1. isotherm
2. isotherm
0.0 0.2 0.4 0.6 0.8 1.0
Relative humidity [-]
Moisture content [kg/kg]
0.070
0.060
0.050
0.040
0.030
0.020
0.010
0.000
Cellular concrete (absorption)
1. isotherm
2. isotherm
0.0 0.2 0.4 0.6 0.8 1.0
Relative humidity [-]
FIG. 5: Absorption curves at 20 ºC showing the effect <strong>of</strong> <strong>drying</strong> <strong>temperature</strong> on the hygrothermal
behaviour <strong>of</strong> the material. In this case, the 2 nd isotherm has been measured after the sample has been dried
at 70ºC.
materials can sustain this high <strong>temperature</strong> without impact. A newly investigation on gypsum plaster board
(Wilkes et al, 2004) has shown that <strong>drying</strong> at 20 ºC <strong>and</strong> 0 % RH gives what could be conceived as the most
correct answer, if enough time is used for the <strong>drying</strong>. In the actual measurements for this paper, the <strong>drying</strong>
at 20 ºC took about 24h for the IGAsorp <strong>method</strong>. Using the st<strong>and</strong>ard <strong>method</strong>, the end <strong>drying</strong> took 10 – 14
days for insulation materials <strong>and</strong> 1 – 2 months for cellular concrete <strong>and</strong> glass wool (Hansen et al, 1999a).
On the other h<strong>and</strong>, Fig 5 shows that <strong>drying</strong> at elevated <strong>temperature</strong>s does not have any significant effect on
the sorption behaviour <strong>of</strong> the investigated materials, expect for cellular concrete. One possible explanation
for the difference between first <strong>and</strong> second isotherm for cellular concrete is that <strong>drying</strong> at elevated
<strong>temperature</strong>s has removed extra moisture <strong>and</strong> thereby the dry mass m0 for the second isotherm is relatively

smaller. However, there is a slight tendency to that the slope <strong>of</strong> the sorption curve – <strong>and</strong> thereby the
moisture capacity – is increased for all the materials.
The main argument for using rapid <strong>method</strong>s is the wish to reduce the time used for the experiments: While
it takes only few days for IGAsorp, the st<strong>and</strong>ard <strong>method</strong> can take several months, or a year, to execute. On
the other h<strong>and</strong>, it is possible to measure only one sample at time in the IGAsorp while the st<strong>and</strong>ard <strong>method</strong>
makes it possible to make parallel tests for many samples at time. A variation <strong>of</strong> the st<strong>and</strong>ard <strong>method</strong> has
been used at the Technical University <strong>of</strong> Denmark for years: Similar samples are placed in parallel in
desiccators which each contain different saturated salt solutions, corresponding to a certain RH. EN ISO
12571 stipulates another principle where each sample is placed consecutively in a series <strong>of</strong> test
environments. Following the ISO-procedure the test will be very time consuming compared to the
alternative procedure.
5. Conclusion
This paper has dealt with an investigation <strong>of</strong> the potential importance <strong>of</strong> some parameters on the
determination <strong>of</strong> the sorption curves. The results have shown that while the choice <strong>of</strong> apparatus/<strong>method</strong>
<strong>and</strong> the <strong>step</strong> <strong>size</strong> in RH does not have any particular effect, the <strong>drying</strong> <strong>temperature</strong> used for the
determination <strong>of</strong> the dry mass may have a very significant effect on the results.
6. Acknowledgements
Sorption measurements with the IGAsorp equipment took place at Glasgow Caledonian University with
assistance from Pr<strong>of</strong>. Graham H Galbraith <strong>and</strong> his staff: Dr. David Kelly <strong>and</strong> David Bailly. Measurements
in climatic chambers were assisted by Britta Roll <strong>and</strong> Ulla Gjøl Jacobsen.
7. References
EN ISO 12571:2000: Hygrothermal performance <strong>of</strong> building materials – Determination <strong>of</strong> hygroscopic
sorption properties.
Greenspan, L. 1977. Humidity Fixed Points <strong>of</strong> Binary Saturated Aqueous Solutions. JOURNAL OF
RESEARCH <strong>of</strong> the National Bureau <strong>of</strong> St<strong>and</strong>ards - A. Physics <strong>and</strong> Chemistry, Vol. 81A, No. 1,
January-February.
Hansen E.J. <strong>and</strong> Hansen K.K.. 1999a. Sorptionsisotermer. Del af Varme- og fugttekniske undersøgelser for
alternative isoleringsmaterialer, Report R No 58. (in Danish). Department <strong>of</strong> Structural Engineering
<strong>and</strong> materials, Technical University <strong>of</strong> Denmark
Hansen E.J., Hansen K.K. <strong>and</strong> Padfield T. 1999b. Measured moisture properties for alternative insulation
products. Proceedings <strong>of</strong> 5th Symposium on Building Physics in the Nordic Countries. Göteborg.
Janz, M. 2000. Moisture transport <strong>and</strong> fixation in porous materials at high moisture levels. Ph.D. Thesis,
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Johannesson, B. 2000. Transport <strong>and</strong> sorption phenomena in concrete <strong>and</strong> other porous media. Ph.D.
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University.
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Thesis, School <strong>of</strong> Built <strong>and</strong> Natural Environment, Glasgow Caledonian University
Peuhkuri, R. 2003. Moisture dynamics in building envelopes, Ph.D. Thesis, Report R-071, Department <strong>of</strong>
Civil Engineering, Technical University <strong>of</strong> Denmark. http://www.byg.dtu.dk
Strømdahl, K. 2000. Water Sorption in Wood <strong>and</strong> Plant Fibres, Ph.D Thesis, Report R No 78, Department
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