Dew point in insulation block

[Knut57]

Hello, regarding new construction.

1) Wondering about the dew point in insulation blocks like Finja Exact and others. I've heard that there can be issues with moisture accumulating on the inside of the insulation, and I’m curious since Finja support seems to be completely unresponsive to the question and has no answer...

2) How does moisture migration work in lightweight concrete like Siporex and Bauroc? Is the wall sufficiently tight, or is a moisture barrier needed?

The current climate zone should affect whether certain moisture saturation doesn’t get out before winter and causes frost damage...

Best regards//Knut

PS Have searched without finding any current thread...

 

[huggan]

The condensation point can be calculated, but you need to know the entire construction of the road. Then it is only possible to calculate at specific RF values and temperatures. That Finja seems uncomprehending seems strange, perhaps you haven't gotten in contact with the right person?

 

[Knut57]

The dew point can be calculated, but you need to know the entire construction of the wall. Then you can only calculate on specific RH levels and temperatures. That Finja seems uncomprehending seems strange, perhaps you haven't contacted the right person?

Thanks for the reply!

The construction is intended to be as per each manufacturer's instructions for each product. For Finja, they seem to want to sell their rendering system, while I interpret that it's possible to plaster directly on their building blocks. It might be that a complete rendering system with mesh and glass fiber cement is a prerequisite precisely to minimize the risk of frost damage? https://www.finja.se/sortiment/betong-och-bruk/putsa-fasad

The choice of plaster hardly affects the dew point and moisture migration to any significant extent.

As I see it, the significant differences between Bauroc and Finja should only be the polystyrene insulation.

Bauroc: https://bauroc.se/product/lattbetongblock-ecoterm/
Finja: https://www.finja.se/sortiment/betong-och-bruk/mura

I have contacted Finja twice myself and once via a timber yard and received the same non-response every time.
Each time, I/we were connected to "support" whether the question was posed openly or, as last time, when I requested contact with an engineer/designer for specific information on dew point and moisture migration.

Any additional tips are greatly appreciated!

Best regards,
//Knut

 

[huggan]

No, the plaster doesn't significantly affect the condensation point. However, I am far from an expert on either plaster or masonry walls. Then again, it could be that the vapor density in the blocks is so high that it never becomes a problem.