Hygric behavior of building materials and their influence on indoor environment
Authors
Nowak, Michal ; Enevoldsen, Magnus Bøgh
Term
4. Term
Education
Publication year
2021
Abstract
This thesis examines how hygric building materials can act as passive regulators of the indoor environment, with a particular focus on relative humidity. Two hemp–lime mixes (for wall and render applications) and two Skamol products (calcium silicate board and moler brick) were characterized through on-site laboratory measurements of sorption isotherms, thermal diffusivity, specific heat capacity, and water vapor permeability, determined using both the traditional wet/dry cup method and an accelerated ODA method; a retardation factor was derived to relate the two approaches. Moisture Buffer Value (MBV) was assessed according to the NORDtest protocol, both in practical tests and via theoretical estimation, and three interior renders were investigated for their influence on moisture transport, including measurement of oxygen diffusion coefficient. The measured properties were partly implemented in dynamic building simulations (BSim) to evaluate impacts on indoor humidity fluctuations compared with constructions with little or no hygric capacity. The results indicate that hemp–lime and calcium silicate materials provide strong moisture buffering, yielding more stable indoor humidity with smaller variations in simulations, while even breathable interior renders can to some extent restrict overall moisture permeability. Where necessary, missing parameters were complemented from the literature.
Denne afhandling undersøger, hvordan hygriske byggematerialer kan fungere som passive regulatorer af det indendørs miljø med særligt fokus på relativ luftfugtighed. To hamp-kalkblandinger (til væg og puds) og to Skamol-produkter (calciumsilikatplade og molersten) blev karakteriseret ved on-site laboratoriemålinger af sorptionsisotermer, termisk diffusivitet, specifik varmekapacitet og vanddamppermeabilitet, bestemt både med traditionel Wet/Dry-cup og en accelereret ODA-metode; forskellen mellem metoderne blev kvantificeret via en retardationsfaktor. Materialernes fugtbufferkapacitet (Moisture Buffer Value) blev vurderet efter NORDtest, både praktisk og ved teoretisk estimering, og tre indvendige pudser blev undersøgt for deres indflydelse på fugttransport, inklusive måling af iltdiffusionskoefficient. De målte egenskaber blev delvist anvendt i dynamiske bygningssimuleringer (BSim) for at vurdere effekten på indendørs fugtvariationer sammenlignet med konstruktioner uden eller med lave hygriske egenskaber. Resultaterne indikerer, at hamp-kalk og calciumsilikat har en markant fugtbufferende virkning, som i simuleringerne gav mere stabile fugtniveauer med mindre udsving, mens selv åndbare indvendige pudser i nogen grad kan begrænse den samlede fugtpermeabilitet. Hvor nødvendigt er manglende materialedata suppleret fra litteraturen.
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