Kuivumiskykyiset ja sateenpitävät rakenteet

Translated title of the contribution: Structures with high drying efficiency and resistance against rain penetration

Tuomo Ojanen, Mikael Salonvaara

Research output: Contribution to journalArticlepeer-review

Abstract

The Building Code of Finland requires five times higher vapour resistance for the material layers inside the thermal insulation as those outside the insulation. Exceptions for this rule are allowed in case the moisture performance of the structure is proved to be safe. The code emphasises also the importance of good drying ability. The highest risks in the moisture performance of a structure are engaged with water or rain penetration from outdoors into the structure and with limited drying efficiency of the structure when compared to the possible moisture loads during the construction and use of the building. An experimental method to study the drying efficiency of structures was developed and a test device was built. This method will be used to analyse and test the moisture transport outwards through the wind barrier layer during the drying phase. Altogether 20 parallel intersection of structures or structure components can be studied simultaneously. The drying of the initial moisture load is monitored under selected warm and cold side temperatures corresponding to realistic conditions. The results show how the moisture that condenses and possibly also freezes on the inner surface of the wind barrier layer affects the drying efficiency. The effective vapour permeability of the wind barrier layer can also be solved. Rain penetration into structure was studied experimentally with a device that produces pressure difference by high air flow hitting the structure surface. The benefit of this method is that the pressure gradients along the siding and at the outer parts of the structure are relatively similar to those caused by the wind. This allows a more liable study of the effects of local pressure gradients on the rain water penetration through structure details. High drying efficiency and rainproof structures improve the control and elimination of moisture risks. If the water vapour diffusion resistance of the wind barrier or other outer layer of the structure is high, the drying efficiency can be significantly improved by arranging limited ventilation through this layer. Even a very low ventilation flow can improve the drying efficiency without affecting the thermal resistance of the structure.

Translated title of the contributionStructures with high drying efficiency and resistance against rain penetration
Original languageFinnish
Pages (from-to)3-66
Number of pages64
JournalVTT Tiedotteita - Valtion Teknillinen Tutkimuskeskus
Issue number2168
StatePublished - 2002
Externally publishedYes

Keywords

  • Construction
  • Driving rain
  • Drying
  • Moisture insulation
  • Rain penetration
  • Rainproof structures
  • Structures
  • Ventilation
  • Water proofing
  • Water vapour
  • Wind barrier

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