19.10.2004 Status on NORDTEST project: Moisture Buffering of Building Materials Carsten Rode Department of Civil Engineering, Technical University of Denmark The following is mainly an extract of the status report sent to the NORDTEST organization by the end of the project’s first phase in the middle of September 2004. The project is currently in a “hibernation phase” since we are waiting for NORDTEST’s approval to continue with Phase 2 of the project (planned for Nov. 2004 – June 2005). The project took an offset in fruitful presentations and discussions carried out at a Workshop in August 2003. From this workshop we knew that the project idea was judicious. Two working meetings have been arranged in the period since the official project start: - At EMPA Zürich, May 14. This was arranged in continuation of a meeting earlier the same week in IEA ECBCS Annex 41. Thus the NORDTEST meeting had participation from a substantial group of external partners, including three members of our international reference group. The minutes of the meeting are attached to this note as Appendix 1. Prior to the meeting was prepared an ”Initial Review Report” with contributions from the project partners. The review report declares the theoretical definitions used in the project, and they were discussed at the meeting. - At Byggforsk, Trondheim, August 16 (minutes of the meeting attached as Appendix 2). The main issues were discussion of the test protocol draft (Appendix 3) and presentations of results and problems of a first comparative test with a reference material. Also first presentation of a computer program for conversion of relevant moisture buffer properties. It has been agreed to submit a paper for the Nordic Building Physics Symposium in June 2005 about the project – an abstract is attached as Appendix 4. In June 2004, the project members were advised by Chris Sanders of Glasgow Caledonian University about a Japanese standard (JIS A 1470-1) on a related topic, which is now proposed as an ISO standard. The project group has discussed the Japanese proposal to find if there is overlap with our ongoing work. There are indeed some similarities in the methods – but also some differences. The Japanese Standard is only for building materials, where our work is for other materials used in indoor furnishing as well. We propose to NORDTEST that our work should be completed as planned. Particularly since some of what is now missing in our project is the round robin testing where data are obtained, and where we will have the most interaction with industry partners who have supported the project, and should benefit from it. Phase II comprises primarily to carry out the round robin testing of typical materials from industry partners, and to write the NORDTEST method (it will consist mainly of the theoretical definitions and the test protocol). Some dissemination activities will take place as well, including planned contribution to a public meeting arranged with Fuktcentrum, Lund, Nov. 22, 2004. The next work phase will be mainly by correspondence and work with local industry contacts, so no further plenary meetings are planned until one in June 2005 – probably in connection with the Building Physics Symposium in Reykjavik. Appendix 1 CAR, June 10, 2004 Minutes of meeting in NORDTEST project on Moisture buffer Capacity, ETH Zürich, May 14, 2004, 13:15 - 17:00 Participants (See IEA Annex 41’s member list: http://www.kuleuven.ac.be/bwf/projects/annex41/members.htm for addresses): NORDTEST partners: Carsten Rode, DTU (chairman) Berit Time, NBI Tuomo Ojanen, VTT Kaisa Svennberg, LTH Lone Hedegaard, DTU Members of international reference group: Andreas Holm, FhG - IBP Nuno Ramos, UP Nathan Mendes, PUCPR Observers: Karim Ghazi Wahili, EMPA Chris Sanders, GCU Mike Davies, UCL Theodore Chen, UCL Olga Koronthalyova, SAS Peter Matiasovsky, SAS Heiko Fechner, TUD Juha Vinha, TUT Arnold Janssens, UGENT Carey Simonson, U of S Jos van Schijndel, TUE Vasco Peixoto Freitas, FEUP-UP Targo Kalames, TTU (Tallin Techn. Univ.) Paul Fazio, Concordia University Kumar Kumaran, NRC Canada Achilles Karagiozis, ORNL Hua Ge, Concordia Evaristo Rodriguez, UDC Agenda: 1. Opening of the meeting 2. Review of project plan and schedule 3. Contractual matters 4. Definition of the term: Moisture Buffer Capacity, incl. its relations to standard hygrothermal properties. 5. Test procedures and round robin tests 6. Involvement of industry 7. Work plan 8. Next meeting 9. Closure 1. Opening of the meeting The meeting was held as an extension to the IEA ECBCS Annex 41 working meeting held at ETH May 1214, 2004. Carsten Rode welcomed the many guests for the meeting, some of whom had also volunteered to act as members of an international reference group for the project since it was fostered at the NORDTEST Workshop at the Technical University of Denmark, August 21-22, 2003. The summary report from the Workshop can be found under: http://www.byg.dtu.dk/publications/rapporter/byg-r067.pdf 2. Review of project plan and schedule Carsten Rode gave an overview of the project (and the NORDTEST organisation and projects in general). The project runs in two phases. Phase I comprises the definition of the term Moisture Buffer Capacity and writing of a proposal for relevant test methods, including relations to standard hygrothermal properties. Phase I must be reported to NORDTEST by September 15, 2004. Phase II is the implementation of the ideas from Phase I: A round robin will be carried out, and the NORDTEST Method will be written and then sent for remiss. Some dissemination activities should be carried out by the end of the project, and comments are invited from the public by the end of Phase I. The whole project should be completed by Summer 2005. 3. Contractual matters The core partners should sign and send their collaboration agreement to DTU. Each partner is responsible for agreements with their national industrial partners. However, we must collect documentation of their financial or in-kind support. We have more or less the anticipated industry participation, but more contributions shall still be welcomed. 4. Definition of the term: Moisture Buffer Capacity, incl. its relations to standard hygrothermal properties. The four core partners had prepared some short review papers before the Zürich meeting, summing up, from the perspective of each partner, the important results of the workshop in August and input from the literature. The papers were collected in a short report "Initial Review of Definitions and Methods" and distributed at the meeting. The subsequent discussion touched on many relevant properties and relevant factors: • Moisture penetration depth, Moisture effusivity, Available water. • The concept of Moisture Buffer Performance was proposed when referring to conditions in whole rooms, and Moisture Buffer Capacity should relate only to individual materials, and possibly to material combinations. However, whole rooms are out of the primary scope of this project, but possibly one could define a concept, such as Active volume, comprising all materials in a room. • There is a problem with how materials are configured geometrically in a room, and their surface film coefficients, surface coatings and other multi-layered structures. • Some possibilities for classification of moisture buffer capacity were proposed by several of the participants, but the topic was not concluded upon. • Also, one could define a reference material to which other materials could compare by a factor – like µvalue for vapour permeability. • How can furniture be treated - possibly as modified air? • It would be relevant to link the buffer performance property to standard hygrothermal properties - one could perhaps do with just the moisture diffusivity. • A calculation tool to make the conversions would be useful, and will be considered by LTH. • One should be aware that the conditions have a non-linear nature. This is relevant for the choice of RH levels at which the tests are to be carried out. Preferably, this should match some realistic saturated salt solutions (e.g. 23, 50 and 75 % RH are possible). To make the discussions converge it was proposed to work towards a dual definition: • A theoretical definition - the moisture effusivity, bm, and • An industrial definition - ∆m8h. The first is a dynamic property of a material, which can theoretically be deduced from vapour transport and sorption properties determined under steady state conditions. However, one should bear in mind that for some materials, properties determined under steady state may not be valid in dynamic situations. bm may not be an intuitive quantity for lay people. The second property simply expresses the quantity of moisture exchange in a given dynamic exposure, e.g. for 8h/16h step changes or, possibly, daily sinusoidal variation. 5. Test procedures and round robin tests Overview of which facilities are available to the project The partners explained which test facilities are available to them: • LTH: Jar method. • NBI: Bigger jars (from Berit’s Dr.Ing.) • VTT: Box for step changes of RH • DTU: Refrigerators and Megacup. In addition, it was indicated that FEUP and IBP had equipment with which they would also participate in the round robin on a voluntary basis. It should be possible for all partners to participate in the project's material testing with the different equipments they have already. Typically: some climatic chambers of various kinds. A question is how the climatic exposure can be controlled, e.g. for step changes. This way, it will eventually also be more feasible for industry to do this kind of testing. Discussion of test protocols. A test protocol must be developed, and we will start this work now. Berit Time prepares a first draft. The effectiveness of the test protocol will be tested already in phase I of the project by the different partners' use of a preliminary round robin material: Tuomo Ojanen will provide some Finnish spruce plywood. The preliminary round robin would possibly be followed up with tests on material from Maxit (Optiroc). 6. Involvement of industry Contracts/agreements with companies Which materials and measurements? Mentioned on the “financing slide of Carsten’s PowerPoint presentation (attached in pdf-format). See also agenda item 3. 7. Work plan Phase I runs until September 2004 (deadline for the interim report is Sept. 15). Deliverables must be planned tightly. See agenda item 2, and Carsten’s PowerPoint presentation. 8. Next meeting NBI, Trondheim, August 16, 2004. 9. Closure Carsten Rode thanked the EMPA and ETH for their kind hospitality in making the facilities available for the meeting, and all the participants for their sincere interest in the topic and the project. Appendix 2 CAR, September 8, 2004 Minutes of meeting in NORDTEST project on Moisture buffer Capacity, Byggforsk, Trondheim, August 15-16, 2004 Carsten Rode, BYG·DTU, Draft - September 1, 2004 Participants: Berit Time, NBI Arild Gustavsen, NTNU (participated until noon August 16) Tuomo Ojanen, VTT Kaisa Svennberg, LTH Jesper Arfvidsson, LTH Carsten Rode, DTU (chairman) Agenda: Sunday, August 15, Common dinner in Trondheim Discussion of status: • The initial review report (pre-Zürich) • Zürich meeting • What needs to be done in the rest of Phase 1 of the project? Monday, August 16 Administrative matters (contracts and industry contacts, status) Moisture Buffer Capacity definition. • What's in it now - and what isn't • Publication for the definition of MBC • Relation to standard moisture transport properties Test methods • Overview of applicable methods (by the partners) • The Japanese/proposed ISO standard • First comparative tests (all partners report their results) • The test protocol document (this should be the focus of this meeting!) • Comments from FEUP • Ideas for follow-up tests (also depends on phase II and the industry involvement) Time plan until September 15 • Deliverables • Status report for NORDTEST • Permission to continue with Phase II • Distribution of duties Public meeting Phase II, overview: • Round robin begins • Industry involvement • Writing of NORDTEST method Sunday, August 15, Discussion of status: The division of the project into two phases, and the content of the two phases, was rehearsed. Phase I with state-of the-art assembly, proposal for a definition of Moisture Buffer Capacity, and proposal for a test protocol should be reported to NORDTEST together with the request for permission to continue with the project’s Phase II. Phase II deals with the actual writing of the NORDTEST method, and round robin testing of reference materials. The intermediate report and renewed application should be sent to NORDTEST by September 15. • The initial review report (pre-Zürich) and issues from Zürich meeting The initial review report will be added as an attachment to the reporting we send to NORDTEST by the end of Phase I. • What needs to be done in the rest of Phase 1 of the project? We need to be very accurate to fulfil the requirements of deliverables by September 15, such that we can foresee a smooth transition into Phase II of the project. Responsibilities will be distributed tomorrow. Monday, August 16 Administrative matters (contracts and industry contacts, status) Each partner is responsible for the industry contacts in their own country. Documentation of the contribution by the industry contacts (whether monetary or in-kind) needs to be collected such that we can prove this contribution to NORDTEST. This documentation should be kept in the files of the individual partners and a copy sent to the project leader (DTU). The partners can send an invoice to DTU for their share of Phase I of the project in connection with the intermediate reporting to NORDTEST. Moisture Buffer Capacity definition • What's in it now - and what isn't We will base the definition on two quantities which supplement each other: bm - Moisture Effusivity This is the theoretical value and can only be determined for a pure material ∆m8h - Moisture Buffer Value. This is a practical value that can be assessed from an experiment (moisture uptake after 8 hour exposure to a new climate) - also possible for composite materials. - A theoretical relation exists between bm and ∆m8h. - The quantities are characteristic of individual materials/surfaces – not assemblies like in complete rooms. The definitions apply not only to building materials, but possibly also to furniture and textiles etc. - We cannot be too precise about the influence of the surface film coefficient, although for some materials it may be an important factor. We will not specify certain test conditions in terms of air circulation, but the effect should be demonstrated. As far as possible materials should be tested under conditions similar to their intended use, and the test circumstances should be reported. (Something like that, was that what we agreed upon…?) - The number is a figure of merit for design. We should demonstrate how it can be used – e.g. come with an example. - A graphic illustration in the form of a scheme will describe the relationship between: - Level 1: The MBC concept - Level 2: Moisture Effusivity and Moisture Buffer Value, respectively - Level 3: Standard hygrothermal properties. - In addition, we could/should introduce yet another number, a, which can be seen as parallel to the capillary water uptake coefficient, i.e. the square time development of moisture uptake. • Publication for the definition of MBC The definition will of course be given as part of the NORDTEST method, when we come to that in Phase II. But already now, we will prepare a paper for the next Nordic Building Physics Symposium (Reykjavik, June 2005), where the definitions will also be given. • Relation to standard moisture transport properties LTH will prepare a program to make the translation between Moisture Buffer Value and standard hygrothermal properties. A first version moistbuf developed by L.-E. Harderup, was demonstrated. The program can read measured results. It can check the surface film coefficient. The program can be distributed to the participants (current version has a decimal point/comma problem). Test methods • The Japanese/proposed ISO standard A Japanese standard (JIS A 1470-1) was proposed to be raised as an ISO standard, and it is quite similar in topic to our work. It was sent to Carsten from Chris Sanders after our Zürich meeting, and afterwards, it also turned out that Arne Elmroth/Margaretha Andersson have had it since Feb. 04 – but they were not aware of our work. The JIS is only for building materials, where our work is for other materials as well. There are some similarities in the methods – but also some differences. Carsten will ask Chris about the current status of the standard in the ISO system. Also, we will inform NORDTEST about the JIS/ISO when we report to them in mid-September. • Overview of applicable methods (by the partners), and • First comparative tests (all partners report their results) VTT, Byggforsk and DTU have the following equipment available by the partners for the initial experimental testing of Moisture Buffer Value: - Byggforsk uses equipment from Berit’s Dr.Ing. work. Specimens are moved between two vessels with different relative humidities, which are maintained by saturated salt solutions. Weighing is done automatically with 10 minutes intervals using a scale with 1 mg resolution. The equipment currently 2 has no fan, so airflow is uncontrollable. ∆m8h = 24.4 g/m was found in 6.5 hours - VTT has equipment where the sample is moved from chamber to chamber. There is a fan, but it is 2 not efficient. ∆m8h = 18.5 g/m was found in 8 h’s. Weighing is manual. Some nice weight vs. square2 ½ root-time curves were obtained, and a was calculated to be 0.110 g/m s . - DTU has refrigerator chambers where the air humidity is controlled by mixing of moist and dry air. The RH control is very accurate but changes take place over some 30 minutes when going from 33 to 75% RH. There is a fan, which in the preliminary testing has been switched off. Weighing is done 2 automatically, e.g. with 5-min. intervals, on a scale with 1 mg resolution. ∆m8h = 26.5 g/m was found in 8 h’s. - LTH was planning to use JAR method and possibly the vial cup, but so far there had been problems, so no results yet. All first tests have been done with 33 / 75% RH setpoints in 16 / 8 hour daily shifts. Each of us shall now continue these first tests so we have three duplicates of the spruce plywood tests with our equipment. All results should be sent to Kaisa who will collect them (hopefully before Sept. 15…?). Tuomo has sorption curve and vapour perm. data for the spruce plywood, and he will send this information to all. It was agreed that for future tests, the results should be reported also pr. % RH change in the exposure. • The test protocol document Comments and discussion were based on the last distributed version of the document (29.06.2004). Comments relate to the section numbers: Title: capacity -> value building materials -> material exposed to indoor air 1. Specify the number of measurements to be done pr. day. 2. Accuracy of the scale: The end result must not be affected by more than 1% 3. Thickness should be at least the moisture penetration depth (which definition?). If not, materials should be used as they would be installed in practice. More specific information needed about sealing. Some info needed about horiz./vertical positioning of the specimen. How many open/sealed faces? Initial equilibrium should be 50 % RH (or 54 % RH), or mean RH of exposure during test. 4. 33 – 75 % RH should be the main choice, but also alternative choices: 33 – 54 % 54 – 75 % 75 – 93 % The choices should reflect probable applications of the material… There should be specified a requirement on the RH accuracy. The tests should last for at least 3 days, and the amplitude of the weight variations must not differ by more than 5% of the specimen weight when comparing the last two days. There should be a minimum of 5 weighings of the specimen in 8 hours on the last day. 4.2 Delete “if possible”. Exposed area should be determined after edge sealing has been carried out. 4.3 Movement to scale must not influence the result by more than 1% of the amplitude. 5. ∆m should be reported pr. m , and pr. ∆RH. 2 Classification: Probably a good idea, but this is future work for when we have the experience. Also report the initial ∆m/sqrt(t) value (or a-value) – this is particular important for thin/lightweight materials. • Comments from FEUP On 23.07.2004 we received the following comments from FEUP, Porto – here with the answers agreed during the meeting: 1. Will the definition of the Moisture Buffer Capacity of building materials, based only on the proposed test procedure, benefit materials that present higher vapour permeability, in detriment of materials that have a higher moisture capacity but less vapour permeability? Perhaps. Can be analyzed. 2. The proposed test looks essentially at the daily cycle, but a season cycle can also be important. Shouldn’t there be a reference to the season cycle performance of the materials? We concentrate on daily cycles. Other periods can then be calculated analytically. 3. We think that the sorption flux density coefficient could also be retrieved from the initial phase of the test, and so maybe that could also be a result from the test? Yes, this will be specified as a possible additional result. 4. We present on table 1, a possibility of combining additional information to the test results. We are changing the limits, but not exactly to those proposed by FEUP. • Ideas for follow-up tests (also depends on phase II and the industry involvement) None, but see the note above about also reporting the a-value (∆m – square time relation). Time plan until September 15 • Deliverables and distribution of duties Responsibilities for the deliverables were distributed: Initial Review Report: Carsten Test Protocol: Berit First test results (spruce): Carsten with input from all collected by Kaisa. Computer program with document that describes relationships to well-known properties: Kaisa and Jesper Abstract for Nordic Building Physics Symposium: Carsten • Status report for NORDTEST and Permission to continue with Phase II Carsten will collect the reporting based on the above-mentioned deliverables and send it to NORDTEST by/before September 15. Public meeting Public meeting: November 22, 2004. The NORDTEST project and theme will be presented as part of FuktCentrum´s public information day in Lund. This year with the theme: “Fuktskyddsdokumentation”. Responsible. Jesper and Carsten Phase II, overview: • Round robin begins Strictly, we don’t have NORDTEST’s permission to continue with Phase II yet. But let us be optimistic and prepare so much that we arrange for the materials to be tested in the next phase to be delivered and preconditioned. Some of them may take some time to equilibrate. • Industry involvement • Writing of NORDTEST method Third common meeting This meeting is meant to be held by the end of Phase II. We will try to arrange this to be held on June 12, 2005 in conjunction with the Nordic Building Physics Symposium in Reykjavik. Appendix 3 September 9, 2004 DRAFT – MEASURING OF MOISTURE BUFFER VALUE FOR MATERIALS EXPOSED TO INDOOR AIR 1. Scope The scope of this NORDTEST method is to evaluate the moisture buffer value for materials exposed to indoor air, i.e. building materials, furniture, curtains etc. The test is intended to simulate daily variations. 2. Field of application The method is applicable to materials intended for use indoor. 3. References ?? 4. Definitions Moisture buffer value in this connection refers to the moisture uptake/release when the material is exposed to a square wave in relative humidity between 33 % and 75 % during 8 hours/16 hours. 5. Method of test 5.1 Principle A test specimen, partly sealed, is exposed to a square wave in relative humidity conditions. The temperature is held constant. Because of the change in RH, the specimen will gain or loose weight. The weight change of the specimen is monitored continuously or by using repetitive weighings. The change in weight can be considered as an expression of the moisture buffer value of the test specimen. 5.2 Experimental equipment A climate chamber/climate box where temperature and RH can be kept constant and where the proposed RH-step can be performed shall be used. Suitable sensors and a logging system to continuously record the temperature and the relative humidity within the test chamber shall be used. The sensors shall be calibrated at regular intervals. An analytical balance, capable of weighing the test specimens with the repeatability of 1 % shall be used. That means for example for a test sample with a change in mass of 1 g per 8 hour a balance with a resolution of 0,01 g or better should be used, correspondingly for a test sample with a change in mass of 10 g per 8 hours, a resolution of 0,1 g or better can be used. The air in the test chamber should circulate and the air velocity should be more than 0,1 m/s. However the air circulation must not disturb the balance. 5.3 Test specimens 5.3.1 General The test specimens shall be representative of the product. 5.3.2 Exposed area The shape and size of the test specimen is not fixed, but rectangular shapes are recommended. The minimum side length or diameter of the exposed area of the specimen is recommended to be 100 mm and minimum exposed face area is 0,01 m2. Representative circular test specimens (homogeneous surfaces) or smaller test specimens can be allowed. 3.3 Sealing of specimen Rectangular test specimens shall normally be sealed on 4 (?) or 5 out of 6 sides. Other test specimens should have as many sides exposed as in the intended use. Sealing materials could be… (wait for the results from Lund towards the end of the year) 3.4 Thickness of test specimens The thickness of the specimen should be at least the moisture penetration depth (which definition ?). Whenever possible, the thickness of the specimen shall be that of the product in use. If the criteria above are fulfilled the following thicknesses can be used: For products/specimens with “non-defined” thickness; Thickness minimum 10 mm For composite products with “non-defined” thickness; An assembly thickness of 10 mm Recommended thickness of the test sample depends mainly on the water vapour permeability of the material measured using the wet cup method (50/97 % RH). The level of the coefficient can be taken from literature or it can be measured. In case of uneven material thickness (panel carvings etc.), the value corresponds to the minimum thickness of significant area of the specimen surface. (3.5 Surface coating of test specimens In some cases the test products may have surface coatings or they may consist of different material layers. The determined result is then not a pure material property. It is recommended to measure the product with and without the coating layer if the disconnecting of the surface layer is possible without causing significant changes to the surface properties of the actual base material. ) 3.6 Number of test specimens A minimum of 3 test specimens shall be tested 3.7 Conditioning of test specimens Before testing, the test specimens shall be stored an initially be in equilibrium with 50 % RH or mean RH of exposure during test. The criteria for equilibrium is a period long enough for the weight of the sample to stabilise so that two successive daily determinations (24 hours between) of the weight agree to within 0,1 % of the mass of the test specimen. 4 Procedure 4.1 Test conditions The test environment is given in Table 3. Set A should be the main choice, but if the application of the material fits better to another set (B, C or D) these could also be alternatives. Table 3 Test conditions Set A B C D Temperature (° C) 23 23 23 23 Low RH (%) 33 33 54 75 High RH (%) 75 54 75 93 Table4: Salt solutions and performance characteristics (Greenspan 1977, Nyqvist 1983 Bertelsen 1984) RH at 20°C [%] 33….. 54,6±0.2 75,5±0.1 94,6±0,7 Salt MgCl2 Mg(NO3)2 NaCl KNO3 Name Magnesium Choride Magnesium Nitrate Natrium Chloride Kalium Nitrate dRH/dT [%/°C] 0.3 -0.03 (?) -0.18 A minimum of 3 cycles (3 times 24 hours) should be performed or until the change in ∆m is less than 5 % between two successive cycles (days) ( Could we have a principle figure here ?). The high RH level should last for 8 hours. The low RH level should last for 16 hours. If not the weight gain/loss are monitored continuously, at least 1 weighing have to be done at each level. There should be a minimum of 5 weighings of the specimen in 8 hours on the last day. 4.2 Preparation of specimen and test facility Prepare test specimens. Measure the thickness and the exposed area after the sealing have been done. 4.3 Test procedure Place the test specimen in the test chamber. Record/Perform the weighing. Weighings shall be carried out in an environment with a temperature within +/- 2 °C of the test condition, wherever possible within the test chamber. Movement to scale must not influence the result by more than 1 % of the amplitude. Plot a curve of the mass against time. 5. Calculation and expression of results The result shall be calculated as mass-change (m8 hours-m0) per m2 and per ∆ RH A result shall be calculated for each cycle. The Moisture Buffer Value is the average of minimum 3 cycles (??the average of the cycles that are within the ± 5 %..) The initial ∆m/sqrt(t) value (or a-value (should be defined earlier)) should be plotted. This is particularly important for thin/lightweight materials. …….. 6. Reporting of the result 7. References Bertelsen, N.H., 1984, Fugttransport målt med kopmetoder. Nordtest workshop, bagrund og udviklingsområder. (Moisture transport measured with cup methods, Nordtest workshop, background and further development issues). Byggeteknik, Teknologisk Institut, Denmark, (In Danish). Greenspan (1977), Humidity Fixed Points of Binary Aqeous Solutions. Journal of Research of the National Bureau of Standards – A. Physics and Chemistry, 81A (1), pp.89-96. Nyqvist (1983), Saturated Salt Solutions for Maintaining Specified Relative Humidities, International Journal of Pharmaceutical Technology and Product Manufacture, 4(2), pp.47-48. Appendix 4 Nordic Building Physics Symposium, 2005 Reykjavik, June 13-15, 2005 --- ABSTRACT --- (draft 14.09.2004) Moisture Buffer Value of Materials in Buildings Carsten Rode, Technical University of Denmark Ruut Peuhkuri, Technical University of Denmark Kurt Kielsgaard Hansen, Technical University of Denmark Berit Time, Norwegian Building Research Institute Kaisa Svennberg, Lund Institute of Technology Jesper Arfvidsson, Lund Institute of Technology Tuomo Ojanen, VTT Technical Research Centre of Finland Building materials and furnishing used in contact with indoor air have an effect to moderate the variations of indoor humidity seen in occupied buildings. Thus, very low humidity can be avoided in winter, as well as can high indoor humidity in summer and during high occupancy loads. 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 figure to characterize the moisture buffering ability of materials. It has been the objective of a recent (ongoing until mid-2005) Nordic project to come up with such a definition, and to declare it in the form of a NORDTEST method. Apart from the definition of the term Moisture Buffer Value, there will also be a declaration of a test protocol which expresses how materials should be tested. Finally as a part of the project, some round robin tests will be carried out on various typical building materials. The paper will give an account on the definition of the Moisture Buffer Value, it will outline the content of the test protocol, and it will give some examples of results from the round robin tests.