RETRACTED: On the estimation of moisture permeability and advection coefficients of a wood fibre material using the optimal experiment design approach

A discussion of “Characterization of hygrothermal properties of wood-based products – Impact of moisture content and temperature”

“…The analysis shows that the corrected surface transfer resistances lead to intrinsic vapour permeabilities in the range of 6•10 -11 s to 15•10 -11 s, dramatically lower than [1]'s original range "between 10 -10 s and 10 -9 s". Additionally, these new values also clearly suggest that the air-gap-corrected permeabilities adopted in [2][3][4][5][6][7][8][9][10][11] are undoubtedly an underestimation. a. b.…”

“…In that paper, hygrothermal properties of wood-based products were measured, including the sorption isotherm and vapour permeability of wood-fibre insulation. In the four years since that publication, these results have been referenced frequently [2][3][4][5][6][7][8][9][10][11]. The present author contends though that the study in [1] contains flaws in the measurement, calculation and presentation of the vapour permeability of woodfibre insulation.…”

“…Notwithstanding that the intrinsic vapour permeabilities calculated above have been shown to be incorrect, the analysis offers strong indications that the widely adopted air-gap-corrected vapour permeabilities of wood-fibre insulation [2][3][4][5][6][7][8][9][10][11] in most cases significantly underestimate the actual intrinsic permeabilities. And such underestimation may have important ramifications for these studies' findings and conclusions, the extent of which depends on the actual application.…”

“…They are moreover not the primary interest for researchers and practitioners, which (almost) always require intrinsic permeabilities. It will be demonstrated below that most researchers who use [1]'s permeabilities [2][3][4][5][6][7][8][9][10][11] did not distinguish between the provided air-gap-corrected values and the desired intrinsic values. This lack of distinction is probably also exacerbated by an additional presentation flaw: in Tables 4 and 6 in [1] these air-gap-corrected permeabilities are used for calculating the water vapour resistance factor μ, while EN ISO 12572 [12], and equation 8 in [1], prescribe its calculation from the intrinsic permeability instead.…”

“…The present author contends though that the study in [1] contains flaws in the measurement, calculation and presentation of the vapour permeability of woodfibre insulation. These have led to the wider adoption of incorrect permeabilities [2][3][4][5][6][7][8][9][10][11], which in turn have resulted in debateable claims, on the inaptitude of stationary vapour diffusion experiments [8,10] and on the importance of advection in hygroscopic ad-/desorption [9,11]. The goal of this discussion is to reveal the erroneous measurements, calculations and presentations in [1] as well as to discuss the ramifications for the investigations [2][3][4][5][6][7][8][9][10][11] making use of [1]'s outcomes.…”