Towards Development of Methods for Assessment of Moisture-Originated Damage

    Published: Jan 2009

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    OVER THE PAST YEARS, CONSIDERABLE EFFORTS have been made to promote the design and construction of high quality buildings meeting an array of performance criteria. Energy efficiency, indoor air quality, durability, functionality (serviceability), and safety issues became issues challenging researchers and designers within a framework of overall sustainability and cost awareness. Design and construction of a building with regard to a selected performance (e.g., U value) deals with the prediction (during the design stage) and control (after construction) of this quantity with respect to a selected reference value (performance criterion). IEA-Annex 32 [1] listed the following hygrothermal performances for building enclosures: airtightness, thermal resistance (level of thermal insulation), transient thermal response, moisture response of the assembly, and effects of thermal bridges in the assembly. Hens and Carmeliet [2] give an example of such an integrated performance evaluation for masonry with EIFS (Exterior Insulation and Finish System). Moisture performance assessment presented in IEA-Annex 32 [1] includes the analysis of the structure or material exposed to eight different moisture loads: built in moisture, ground source moisture, wind driven rain and precipitation, sorption from ambient air (surface phenomena), and interstitial condensation as well as miscellaneous moisture sources (moist air or rainwater infiltration). Performance requirements, reference values and good moisture practice guidelines were also presented in IEA-Annex 32 [1]. Advanced heat, air, and moisture (HAM) transport simulation tools take into account all these moisture loads including unexpected events (e.g., rain leakage). This document also mentions the growing awareness of the probabilistic character of “moisture design.” In IEA-Annex 24 [3], a methodology to link these HAM transport models to durability evaluation tools was mentioned. The rationale for a performance based durability assessment included the following steps: (1) the selection of the expected period of life (design life); (2) the identification of the different mechanical loads, environmental actions and damage mechanisms; (3) the prediction of the service life either by simple deterministic or more advanced stochastic models. Although IEA-Annex 24 [3] and IEA-Annex 32 [1] recognized the importance of durability, these reports address only general concepts of durability. IEA-Annex 32 [1] mentions that future advanced HAM tools should be developed from a durability perspective and include a risk versus elapsed time analysis. In a first approach to moisture durability assessment, Bomberg and Allen [4] and Allen and Bomberg [5] extended the limit states design methodology, that is well established in structural design, to the field of moisture durability. Limit states approach requires the selection of the damage mechanism (process of deterioration) and quantify it with the help of a damage evolution function. A damage criterion (also called the performance criterion) is selected, which defines the pass∕fail criterion for the analyzed performance aspect.

    Author Information:

    Carmeliet, Jan
    Katholieke Universiteit Leuven, Heverlee,

    Chair of Building Physics, ETH Zürich,

    EMPA Material Science and Technology, Dübendorf,

    Roels, Staf
    Katholieke Universiteit Leuven, Heverlee,

    Bomberg, Mark T.
    Syracuse University, Syracuse, NY

    Committee/Subcommittee: E06.41

    DOI: 10.1520/MNL11568M

    CrossRef ASTM International is a member of CrossRef.

    ISBN13: 978-0-8031-7004-9