Moisture Performance Requirements for Insulation in Exterior Wood-Frame Walls without a Vapour Barrier

Anna E. Leszmann*, Martin Morelli, Torben Valdbjørn Rasmussen

*Corresponding author for this work

Research output: Contribution to journalConference article in JournalResearchpeer-review

2 Citations (Scopus)
162 Downloads (Pure)

Abstract

An increased interest has been observed, especially among architects, in constructing the building envelope without using a vapour barrier membrane of polyethene (PE) foil. An increasing interest in biogenic building materials has also been expressed, as their use, besides storing embedded carbon, can reduce greenhouse gas emissions, replacing nonrenewable building components. Further, building envelope construction without a vapour barrier reduces expenses and the difficulty of the work process, especially around joints and penetrations. This study aims to determine the most important material properties of biogenic thermal insulation materials that influence the moisture-robustness of exterior wood-frame walls constructed without a vapour barrier. A literature study was performed to examine which material parameters have the most influence on the moisture conditions in an exterior wall without a vapour barrier. Hygrothermal simulations of lightweight exterior walls were performed to investigate the significance of variations in material properties (e.g., equilibrium moisture content and vapour diffusion resistance) and determine their necessary characteristics when used as thermal insulation material in an exterior wall without a vapour barrier in internal humidity class 3 (defined in EN ISO 13788). The moisture-robustness of the construction is assessed based on the risk of mould growth in the layer between the thermal insulation and wind barrier. The study suggests that the moisture capacity of the available common biogenic thermal insulation materials does not significantly affect the overall moisture performance of the wall. Simulations demonstrate that, for the thermal insulation layer in internal humidity class 3, at least one of the following requirements must be met to ensure moisture-robustness in exterior walls without a vapour barrier: (I) high diffusion resistance of the thermal insulation and (II) high moisture capacity of the thermal insulation material at relative humidity between 60% and 90%. Commercial biogenic thermal insulation materials on the market do not meet the latter requirement.
Original languageEnglish
Article number012115
Book seriesJournal of Physics: Conference Series
Volume2654
Issue number1
Number of pages9
ISSN1742-6596
DOIs
Publication statusPublished - 13 Jun 2023
Event13th Nordic Symposium on Building Physics, NSB 2023 - Aalborg University - CREATE, Aalborg, Denmark
Duration: 12 Jun 202314 Jun 2023
Conference number: 13
https://www.en.build.aau.dk/web/nsb2023

Conference

Conference13th Nordic Symposium on Building Physics, NSB 2023
Number13
LocationAalborg University - CREATE
Country/TerritoryDenmark
CityAalborg
Period12/06/202314/06/2023
SponsorAirmaster , COMSOL, RAMCON, Realdania, Velux, WOODSENSE, RAMCON A/S, Comsol AB
Internet address

Keywords

  • Moisture Performance
  • Requirements
  • Thermal Insulation
  • Wood-Frame Walls
  • Exterior
  • without Vapour Barrier

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