Hygrothermal Behaviour of Ventilation Cavities in Highly Insulated Envelopes

Klaus Viljanen*, Xiaoshu Lü, Jari Puttonen

*Corresponding author for this work

Research output: Contribution to journalConference articleScientificpeer-review

1 Citation (Scopus)
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This article presents long-term experimental studies on the moisture safety in the ventilation cavities of highly insulated (HI) structures. The tested HI-walls had thermal transmittances of 0.11-0.13 W/m2K. A wall with a thermal transmittance of 0.23 W/m2K represented the baseline wall in the test. In addition to walls, an HI-roof of a newly built house with a U-value of 0.08 W/m2K was measured. The results indicate that, in the ventilation cavity, the relative humidity of an HI-wall exceeds 1-7% of the humidity measured from the baseline wall during winter, which coincides with the 0.4-1.5°C lower temperatures observed in the HI-walls. The mold risk in the ventilation cavities of the walls is low, as the value of the mold index (MI) remains below one, which indicates small amounts of microscopic mold only on surfaces. However, at the bottom of the cavity, the MI value reaches 1.4 due to lower temperatures. In the HI-roof, the MI values are between 1.0 and 2.0 in the middle of the cavity in winter. The reasons for the higher mold risk of the roof are the humid weather, the built-in moisture of the roof and the low heat flux from inside. The study confirms that, in the future, warmer weather and increased humidity can increase moisture risks in the ventilation cavities. The results support the use of materials that are more resistant to mold in the outer parts of structures.

Original languageEnglish
Article number07003
Number of pages10
JournalE3S Web of Conferences
Publication statusPublished - 30 Jun 2020
MoE publication typeA4 Article in a conference publication
EventNordic Symposium on Building Physics - Tallinn, Estonia
Duration: 6 Sep 20209 Sep 2020
Conference number: 12


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