Lime Plaster on Wood-Fiber Insulation
a second question for me…I have been chasing an answer in the outside world and realize there may be some knowledge here that can help me.
For our house in the high desert we’re hoping to use wood fibre external insulation. In my research I discovered that a few of the European companies that makes Wood fiber produce sheets that are dense enough…and specifically designed…to take a lime plaster. There is no need to apply lath…only to embed fiberglass mesh. Global Wholesale in Maryland is a supplier of one of these…but no one imports the specific Lime Plaster systems they use in the UK or EU. So I’ve been talking to plaster suppliers and have a couple of lines on pure-lime plasters that should work nices.
But interestingly, Steico UK, the British arm of the company that supplies the sheets actually REFUSED to recommend any plasters for the American Market, citing EIFS/STO lawsuits. I looked them up and they seem to revolve around Portland cement based systems applied without a rainscreen of any kind to vent the air behind the product. I guess in the Northwest they’ve had trouble with moisture and the attendant rot and mold.
There seems to be no problem with the Lime-based plasters (or Renders as they call them in the UK) and the wood fiber board overseas. So I’m thinking the problem is with the cement.
Does anyone know if lime plaster is breathable enough, when applied to wood fiber that there would be ample permeability? Or should I be thinking of putting something (even tyvek stucco wrap) behind the insulation to provide some air movement?
I’d love to know your thoughts.
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