Moisture content changes of beech and ash elements during two years in room conditions

Goran Milic

doi:10.2298/gsf2123097m

Abstract

The subject of this paper is the analysis of moisture content (MC) changes of beech and ash wood during two years in room conditions (heating during winter; no air conditioning during summer). The registered MC changes are primarily the result of changes in relative humidity of the air (measured by capacitive probes). The average relative humidity of the air in the interior is lower today than in the past, as also shown in this experiment (the average relative humidity of air during two years was 44%). The lowest wood MC was reached on very cold winter days when the heating was on even during the night - between 5% and 6%, and the highest one at the beginning of June: 10.4-10.9%. As expected, the wood did not reach equilibrium moisture content - during winter, MC is by about 1% higher, and in summer it is lower by up to 2.5% than the equilibrium. The recommendation that the sawn timber from which the interior products will be made should be dried at 7-8% MC was confirmed.

Highlights

As a consequence of changes in the relative humidity of the air in the interior, there have always been problems caused by moisture content (MC) changes of wood used in finished products
The wood did not reach equilibrium moisture content – during winter, MC is by about 1% higher, and in summer it is lower by up to 2.5% than the equilibrium
Based on the average values, a curve of MC humidity exist within 24 hours as well, because at change over time was formed for beech and ash night

Summary

Introduction

As a consequence of changes in the relative humidity of the air in the interior, there have always been problems caused by moisture content (MC) changes of wood used in finished products. As an illustration of the changed climate in interiors, it is enough to state the parameters of the so-called room climate (t = 20°C, RH = 65%) These conditions, at least for our climate area, are no longer realistic, i.e. the average relative humidity in the interior (in winter due to heating, in summer due to cooling) is certainly lower, often below 50%. This is reflected on wood MC, and the average equilibrium moisture content (EMC) during the year in most apartments is around, or even below 8%. In the following years, the wood floor MC is gradually reduced, i.e. it dries out and shrinks, which again leads to problems, in the form of gaps between the elements

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Conclusion