The moisture buffer capacity of hygroscopic materials and the potential to reduce heating, cooling and ventilation loads has been discussed the last decade. Hygroscopic materials can moderate the levels of indoor relative humidity reveals that the moisture produced in a space is not directly transferred to the ventilated air as assumed in current ventilations design methods. Since heat and moisture transfer are coupled, the indoor temperature will increase when moisture accumulates in the hygroscopic structure and decrease when moisture is dried from the structure, both resulting in lower air enthalpy. Moisture accumulation in wooden surfaces release energy and a potential of direct energy gain rises up. Sauna is a characteristic example of the latent heat phenomena that takes place in surfaces indoors. In this paper, measurements in a Norwegian sauna have been conducted and presented hereby. The focus of the study is on the intense increase of temperature when water is getting bounded in the hygroscopic structure. Different moisture protocols are simulated using a hygrothermal model and the results are compared with the experimental. The surface temperature increase varies between 2 up to 3°C when vapour absorption occurs. Furthermore, the first 5mm of the spruce cladding are characterized by the most highest temperature increase because of latent heat phenomena. The wooden cladding functions as a ‘natural’ heating panel.
Keywords: wood paneling, moisture absorption, latent heat, hygrothermal analysis, sauna physics
Authors
Kraniotis D.
Department of Buildings and Markets, Norwegian Institute of Wood Technology, Oslo
Nore K.
Department of Buildings and Markets, Norwegian Institute of Wood Technology, Oslo
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