Moisture buffer value of building materials

When building materials are in contact with indoor air they have some effect to moderate the variations of indoor humidity in occupied buildings. This way, materials can be used as a passive means of establishing indoor climatic conditions, which are comfortable for human occupancy, or for safe storing of artefacts which are sensible to humidity variation. But so far there has been a lack of a standardized quantity to characterize the moisture buffering ability of materials. It has been the objective of a recent Nordic project to define such a quantity, and to declare it in the form of a NORDTEST method. The Moisture Buffer Value is the figure that has been developed in the project as a way to appraise the moisture buffer effect of materials. The value has a rather practical definition which will be described in the paper. Theoretically, the Moisture Buffer Value has a relationship with other well known properties for moisture transport and storage, and these relations will be explained. The project also comprises definition of a test protocol which expresses how materials should be tested for determination of their Moisture Buffer Value. Finally, it has also been a part of the project to carry out some Round Robin Tests on various typical building materials, and the paper will present some of the results.