HUMIDITY CONTROL EFFICIENCY OF LOW-DENSITY PARTICLEBOARDS FOR INTERIOR WALLS .1. MEASUREMENTS IN ANAIRTIGHT EXPERIMENTAL ROOM

Low-density particleboards (LDPB) are expected to be used for interior walls controlling humidity in houses because they have great moisture permeability which gives rapid rates of adsorption and desorption. In this paper, the advantages of LDPB for humidity control are compared with those of wood lining board (WLB, Japanese red pine, Pinus densifl ora S. and Z.) by measurements of relative humidity (RH) followed by t emperature change (T) in an airtight experimental room (volume: V = 18 .1 m3) using various interior wall areas (A ; m2). Humidity control ef ficiency was evaluated by the slope (B) of the equation representing t he relationship between the logarithms of RH and T and by the size of the RH changes in a day (DELTA RH(c)), and it was discussed in relatio n to the ratio of area to volume (A/V). Although the value of DELTARH( c) and B decreased with increasing A/V, the decrease which indicates a n increase of humidity control efficiency was outstanding in the range of A/V from 0 to 0.6 on both LDBP and WLB. It was found that the humi dity control efficiency of LDPB was superior to WLB. Especially in the range of A/V under 0.6, LDPB showed an effect equal to WLB by approxi mately two-thirds of the interior wall area. The amount and rate of ad sorbed or desorbed moisture by the interior materials were calculated considering the moisture balance of the room. It was shown that the am ount of adsorbed or desorbed moisture per unit area increased with dec reasing A/V, which suggests that humidity control by less area require s thicker materials. Additionally, the influence of painting on the hu midity control efficiency of WLB was investigated. It was found that c oating the wood with urethane resin reduced the effect remarkably, but coating it with alkyd resin did not.