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Frost formation and condensation in stone-wool insulants: the course of moisture resistance factor
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
2008 (English)In: Proceedings of the 2008 World Sustainable Building Conference, 2008, 1035-1039 p.Conference 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.

Place, publisher, year, edition, pages
2008. 1035-1039 p.
Keyword [en]
stone wool, material properties, frost formation, condensation, moisture resistance factor
National Category
Building Technologies Other Materials Engineering
URN: urn:nbn:se:kth:diva-11679OAI: diva2:279223
QC 20100818Available from: 2009-12-02 Created: 2009-12-02 Last updated: 2010-08-18Bibliographically approved
In thesis
1. Condensation and frost formation in fibrous thermal-insulation materials
Open this publication in new window or tab >>Condensation and frost formation in fibrous thermal-insulation materials
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.
Trita-BYMA, ISSN 0349-5752 ; 2009:1
Fibrous thermal insulation, Stone wool, Cellulose, MAterial properties, Moisture transport, Condensation, Frost formation, Exterior conditions, Interior conditions
National Category
Civil Engineering Other Materials Engineering
urn:nbn:se:kth:diva-11632 (URN)978-91-7415-468-9 (ISBN)
Public defence
2009-12-11, F3, Lindstedtsvägen 26, KTH, Stockholm, 13:00 (English)
Disputationen indragen.Available from: 2009-12-02 Created: 2009-11-26 Last updated: 2012-03-22

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Vrána, Tomáš
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