Research into thermal conductivity and moisture permeability of different mattress structures

The primary function of a bed is to fulfil the human need for rest and sleep, as well as for his full renewal of strength through a supported lying position with a minimum of energy consumption. This goal is achievable if the mattress conforms with certain anthropometrical and physiological-hygienic requirements. We have focused our scientific research on the topic of sleep, studying in particular: the exudation of liquid and thermal exchange as a physiological occurrence, the conditions in the sleep environment, and thermal conductivity and moisture permeability through the materials currently used in upholstered furniture. The paper presents the results of the experiment in which the thermo-physiological properties of four different mattress structures were compared. One sample has a pocket spring core and three have the Bonell core, and all four have a different construction of filling materials. The test consisted of measuring the thermal conductivity and moisture permeability during the sleeping period of a woman (36 years old) over a period of six nights. The measurements were carried out applying a specially designed device with sensors which were placed in pairs (one for heat and one for moisture) on six positions relative to the body of the person: in the ambient, in the cover, under the sheet, under the upholstered cover, inside the spring core and under the mattress. The obtained results were analysed for each sensor separately and a comparative review of results for each sample was prepared. Based on these results, the following may be concluded. The best thermal accumulation was achieved in the bed with the pocket spring core (shown by the sensor inside the structure). The same structure showed the highest temperature values at all remaining thermal sensors as well. A high concentration of humidity (60%) was recorded in the central layer of the mattress, pointing to the fact that particular care should be given to the construction of the core by the appropriate selection of materials (the least possible use of PU). The sensor placed beneath the subject recorded significantly higher moisture values for samples with pocket core because of the additional 5 mm of a PU layer. The research carried out confirms the fact that the materials that the cover and upper part of the mattress are made of, are very important for the thermophysiology of sleep and proves the advantage of structures with natural materials.