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Condensation and frost formation in fibrous thermal-insulation materials
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering. (Byggnadsmaterial)
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Heavily insulated constructions are at present being used to strike at the vast energy consumption in residential buildings and commercial alike. They introduce a high-thickness layer of thermal insulation in the building envelopes. Such constructions have great moisture capacity and could be at risk due to moisture leakages and other moisture related problems connected to bad design, climate effects, extended construction period to late autumn and winter seasons and mishandle of building materials.

Thermal-insulation materials based on stone wool and cellulose are commonly used in a wide range of applications that harness their high thermal-insulation properties. Both these materials could be fault-prone due to their fibrous structure in case of moisture problems – e.g. built-in moisture, annually repeating condensation and frost formation in the cold climates.

The aim of this research was to observe the stone-wool and cellulose specimens in various temperature fields under extreme moisture load and to explore the issue of moisture transport and real moisture properties of the tested materials when condensation and frost formation occur. A special testing device, Thermobox, was constructed and the fibrous samples were exposed to temperature gradients simulating real conditions. The climate data as well as the moisture-transport data were registered. They were used in calculations of moisture resistance factor, µ, denoting permeability of the tested samples in the defined moist conditions. Following the laboratory measurements, a mathematical simulation was done to compare total moisture accumulation in the specimens with the practical measurements and to be able to simulate these processes in a longer time interval. Besides, a special outdoor experiment concerning the effect of outdoor climate on the stone-wool structure was executed.

Final research findings proved that the phenomenon of frost formation can exist in the fibrous insulation materials. Moisture transport properties of stone wool and cellulose were affected by the extreme water condensation and freezing, but they remained highly permeable. As regards the moisture storage in the samples, this process was continuous during the tested period and it indicated significant growth of the total water accumulation in connection with dry densities of the tested materials. This emphasises the importance of proper handling with the fibrous thermal-insulation materials and keeping them dry.

Place, publisher, year, edition, pages
Stockholm: US-AB , 2009. , 43 p.
Series
Trita-BYMA, ISSN 0349-5752 ; 2009:1
Keyword [en]
Fibrous thermal insulation, Stone wool, Cellulose, MAterial properties, Moisture transport, Condensation, Frost formation, Exterior conditions, Interior conditions
National Category
Civil Engineering Other Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-11632ISBN: 978-91-7415-468-9 (print)OAI: oai:DiVA.org:kth-11632DiVA: diva2:278519
Public defence
2009-12-11, F3, Lindstedtsvägen 26, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
Disputationen indragen.Available from: 2009-12-02 Created: 2009-11-26 Last updated: 2012-03-22
List of papers
1. Impact of moisture on long term performance of insulating products
Open this publication in new window or tab >>Impact of moisture on long term performance of insulating products
2005 (English)In: Proceedings of the Nordic Symposium on Building Physics, Reykjavik, 2005, Vol. 1, 71-77 p.Conference paper, Published paper (Refereed)
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-7484 (URN)
Conference
The 7th symposium on Building Physics in the Nordic Countries - Reykjavík, June 2005
Note
QC 20100818Available from: 2007-09-19 Created: 2007-09-19 Last updated: 2010-11-22Bibliographically approved
2. A laboratory equipment for the study of moisture processes in thermal insulation materials when placed in a temperature field
Open this publication in new window or tab >>A laboratory equipment for the study of moisture processes in thermal insulation materials when placed in a temperature field
2008 (English)In: Construction and Building Materials, ISSN 0950-0618, Vol. 22, no 12, 2335-2344 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this paper was to describe design and use of a laboratory set-up that makes a very well controlled moisture load to detect material properties of thermal insulation materials. The outer shell of the set-up is a plastic box with thermal insulation on its outer side. This box is placed on a balance for recording of weight loss of the entire system. The sample to be tested is placed on top of this box. The inside of the box is heated electrically and the air circulation is driven by a fan. There is a water reservoir in the box, which is also placed on a balance in order to record the amount of moisture added to the air in the box. To obtain the highest moisture contents it was found necessary to use a wick in the reservoir that increases transport of moisture to the air in the box. The whole set-up was placed in a climate chamber in order to get well controlled temperature and moisture content for the outside of the box. In this way, well controlled gradients of temperature and moisture content in air were achieved around the specimen. The set-up was found to function well and was in this study useful for measurement of the samples moisture resistance factor.

Keyword
Moisture properties, Moisture transport, Test equipment, Thermal insulation
National Category
Building Technologies Materials Engineering
Identifiers
urn:nbn:se:kth:diva-7486 (URN)10.1016/j.conbuildmat.2007.10.007 (DOI)000259168500007 ()2-s2.0-48549093448 (Scopus ID)
Note
QC 20100818Available from: 2007-09-19 Created: 2007-09-19 Last updated: 2010-11-22Bibliographically approved
3. Frost formation and condensation in stone-wool insulants
Open this publication in new window or tab >>Frost formation and condensation in stone-wool insulants
2009 (English)In: Construction and building materials, ISSN 0950-0618, Vol. 23, 1775-1787 p.Article in journal (Refereed) Published
Abstract [en]

This paper reports on a laboratory experiment concerning frost formation and moisture condensation in fibrous insulation based on stone–wool. Frost formation in samples of stone–wool open to air was noted in cases when temperature field over the specimen was between +20 and −20 °C and air on the warm side was saturated with moisture.

Frost accumulated with time in the part of the specimen facing the cold air. In the part of the specimen facing the warm humid air condense formation occurred. In this part the material had moisture content considerably higher than what could be anticipated from data such as moisture isotherms.

Border between frost and liquid condensate was quite sharp in the specimens of higher density. Moisture content mass by mass has an upward trend with decreasing density of the material sample. Moisture resistance factor was found to be quite high at these circumstances. Reason for this is not clear.

Keyword
Stone–wool; Material properties; Frost formation; Condensation; Moisture transport; Moisture capacity
National Category
Materials Engineering Building Technologies
Identifiers
urn:nbn:se:kth:diva-7487 (URN)10.1016/j.conbuildmat.2008.10.014 (DOI)000264786100010 ()2-s2.0-59649115607 (Scopus ID)
Note
QC 20100818Available from: 2007-09-19 Created: 2007-09-19 Last updated: 2012-01-18Bibliographically approved
4. Frost formation and condensation in stone-wool insulants
Open this publication in new window or tab >>Frost formation and condensation in stone-wool insulants
2008 (English)In: Proceedings of the 8th Symposium on Building Physics in the Nordic Countries, 2008, 473-480 p.Conference paper, Published paper (Refereed)
Abstract [en]

Practical experience from building sites show evidence of negative effects of moisture condensation oninsulating materials with fibrous structure. Condensed moisture, as well as moisture trapped in thermalinsulation during construction, can results in serious reduction of thermal properties and, in consequence,systemic upset of living qualities in dwellings. It can also result in increased dust contamination, algae or mouldgrowth and structural damages due to a frost formation of condensate happening in winter periods.

This contribution reports on a laboratory experiment aimed at growth of frost formation and moisturecondensation in stone wool opened to air for specific temperature fields (+20; -20ºC), (+20; -15ºC), (+20; -10ºC) over stone-wool specimens with varying density during a testing period that lasted 100 hours. Air on thewarm side was saturated with moisture. In the part facing the warm humid air condensate formation occurred,while frost accumulated with time in the part of the specimen facing the cold air. Transition between frost andliquid condensate was clearer in the stone-wool specimens of higher density and for tests with broadertemperature fields. Moisture resistance factor μ, a basic moisture characteristic of an insulating material, alsohad an upward trend for broader temperature intervals.

Deeper knowledge about the phenomenon of frost formation in stone wool can help to insight into actualproblems in the building sector resulting from usage of thermal insulations with high thicknesses.

Keyword
Stone wool, material properties, frost formation, condensation, moisture transport.Symposium
National Category
Materials Engineering Building Technologies
Identifiers
urn:nbn:se:kth:diva-11667 (URN)
Note
QC 20100818Available from: 2009-12-02 Created: 2009-12-02 Last updated: 2010-08-18Bibliographically approved
5. Frost formation and condensation in stone-wool insulants: the course of moisture resistance factor
Open this publication in new window or tab >>Frost formation and condensation in stone-wool insulants: the course of moisture resistance factor
2008 (English)In: Proceedings of the 2008 World Sustainable Building Conference, 2008, 1035-1039 p.Conference paper, Published paper (Refereed)
Abstract [en]

Globally increasing prices of energy have result in raise of thermal qualities of building envelopes.Consequently, these heavy insulated constructions are facing undesirable phenomena – for instance a riskfor occurrence of frost formation and condensation together with a changed thermal field in buildingconstructions. Condensed moisture, as well as moisture trapped in thermal insulations during build-up, canalso affect an increased dust contamination, algae or mould growth and structural damages.

This contribution reports on a laboratory experiment aimed at growth of frost formation and moisturecondensation in stone wool opened to air for specific temperature fields – namely (+20; -20ºC), (+20; -15ºC),(+20; -10ºC), (+20; -5ºC) over fibrous specimens with varying density. Air on warm side of material sampleswas saturated with moisture. Frost accumulated with time in the part of specimens facing the cold air. In thepart facing the warm humid air a condense formation occurred. The wider thermal field and higher density ofmaterial samples we used the more distinct border between frost and liquid condensate we observed. Alsomoisture resistance factor μ, as a basic moisture characteristic of an insulating material, had an upwardtrend for broader temperature intervals.

Next to the loss of insulating qualities, annual repetition of condensation and frost growth in stone wool cancontribute to degradation of the material structure, thermal losses and, in consequence, higher energyconsumption.

Keyword
stone wool, material properties, frost formation, condensation, moisture resistance factor
National Category
Building Technologies Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-11679 (URN)
Note
QC 20100818Available from: 2009-12-02 Created: 2009-12-02 Last updated: 2010-08-18Bibliographically approved
6. Stone-wool insulation under offence of massive condensation and ice formationand their impact on moisture properties
Open this publication in new window or tab >>Stone-wool insulation under offence of massive condensation and ice formationand their impact on moisture properties
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Building constructions are often under the offense of condensation. In extreme cases, watercondensation can also be accompanied by formation of frost in layers adjacent to outdoorsurfaces. In general, these problems happen due to sudden climate changes during buildingworks, misuse of building materials or delayed work on sites. Troubles with moisture proceedin the layer of thermal insulation thanks to its high moisture capacity and material thickness.Mineral wool is one of the most used thermal insulation materials in the building industry.Previous research and measurements have proved that fibrous insulations (e.g. stone wool)have varying material properties, when wet. Both thermal and moisture properties arechanged.

This paper refers to laboratory tests concentrating on existence of frost formation in stonewoolspecimens exposed to extreme moisture load and temperature gradients (Vrána, Björk,2008). The executed research of that study did show that moisture resistance factor (μ-valueor μ-factor) is affected by condensation and freezing in the material. This paper illustrates acalculation model based on the monitored indoor and outdoor data (surface T and RH) of thetested materials. These climate data were used to create a functional mathematical model thatcan simulate moisture balance of stone wool. Finally, the model was compared to outputobtained from laboratory measurements.

Keyword
Stone wool, Material properties, Frost formation, Condensation, Moisture transport, μ-value, Sorption curves
National Category
Building Technologies Materials Engineering
Identifiers
urn:nbn:se:kth:diva-11680 (URN)
Note
QC 20100818Available from: 2009-12-02 Created: 2009-12-02 Last updated: 2010-08-18Bibliographically approved
7. Comparison of fibrous insulations: cellulose and stone wool in terms of moisture properties resulting from condensation and ice formation
Open this publication in new window or tab >>Comparison of fibrous insulations: cellulose and stone wool in terms of moisture properties resulting from condensation and ice formation
2010 (English)In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 24, no 7, 1151-1157 p.Article in journal (Refereed) Published
Abstract [en]

Cellulose fibres are often used as thermal insulation in buildings. The organic nature of cellulose fibres, however, makes the insulation sensitive to high moisture content. This study investigates the moisture performance of cellulose insulation when exposed to a subzero environment. The paper is focused on the condensation and freezing in the material and includes comparison with the authors previous studies on stone-wool insulation. While the used stone-wool samples were water repellent due to resin binders,cellulose is a typical representative for hydrophilic thermal insulation to which anycontact with water condensate can be crucial.

Test specimens of loose-fill cellulose were placed in a special laboratory device providing high moisture load. During a period of 100 hours the specimens were subjected to a continuous load of moisture at atmospheric conditions on one side while the other side of the specimen faced a surrounding temperature of 0, -10 and -20°C and the laboratory tests were repeated three times for each set of the specific thermal conditions(Ti=+20°C, Te=0, -10 and -20°C). The results indicate that there are minor changes inthe water vapour permeability of the specimens. The experimental data from the investigation is compared with a mathematical model that simulates moisture diffusivityof cellulose together with accumulation due to sorption and freezing, using the actual climatic data.

Keyword
Cellulose, Stone wool, Material properties, Frost formation, Condensation, Moisture transport, μ-value, Sorption curves
National Category
Materials Engineering Building Technologies
Identifiers
urn:nbn:se:kth:diva-11681 (URN)10.1016/j.conbuildmat.2009.12.026 (DOI)000278039400008 ()2-s2.0-77950459709 (Scopus ID)
Note
QC 20100818Available from: 2009-12-02 Created: 2009-12-02 Last updated: 2017-12-12Bibliographically approved

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Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
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  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
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  • Other locale
More languages
Output format
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  • asciidoc
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