Icynene is breathable
Moisture movement in building materials is directly responsible for structural damage, as well as poor indoor air quality. Icynene allows moisture to pass through individual cells from damp, moist to dry environment thanks to phenomenon called diffusion of moisture (physical phenomenon to balance the pressure difference). After moisture past through Icynene, foam would stay dry as originally installed.
Icynene does not absorb moisture
Water vapour in the air is only the size of the one hundred thousandth degree of water droplets. Due to cell structure Icynene would repeal water in liquid form but would let vapor to pass through. It works in similar way to breather membranes on the roof or Goretex. It is important to mention that Icynene would let water go through if subjected to roof leak or pipe burst (pressure).
In laboratory conditions, the diffusion of moisture through gypsum board was measured by natural diffusion. When a small hole is made in the wall, the amount of moisture that passes through it is multiplied by almost 100! Therefore, it is essential to limit air leaks in buildings. studies by the Canadian government have showed that the consumption of energy (and thus, heating) is directly related to the air tightness of a building.
Do you require VCL when using Icynene? NO.
WUFI® ModelIng Conducted in Germany byThe Fraunhofer Institut Für Bauphysik (report htb 05/2012)
The Fraunhofer Institute conducted WuFI® modeling on Icynene spray foam using weather conditions
of Manchester, UK, the results indicate that installation of a vapour barrier (VCL) is not necessary unless
required by local certification. Indeed, the permeability of H2Foam Lite allows walls to breathe and dry
bi-directionally. In temperate climates except in rooms with high humidity or in poorly ventilated areas,
it is best not to install a vapour barrier since it could trap moisture and cause condensation amongst
other problems. Icynene does not absorb or retain moisture and unlike other insulation products, it helps substantially limit mould growth.