Tips to make Fiber Cement Panel Rainscreen

As you know, there are many kinds of wall systems that are sometimes described as a “rainscreen” since they all direct water out of the system but many designers would reserve that term for only one or two of them. Whatever you want to call them here is a basic simplified summary of what they are to me:

1) Presure equalized rainscreen (PER) - This is a continuously vented/baffled cladding system over an air space detailed so that it allows the pressure on the front and back of the cladding to be equalized reducing the forces that can drive water into a building. This system is recommended where precipitation is over 60 in/yr. Because the detailing is sophisticated and expensive it is rarely used in residential construction even in expensive homes. The commercial systems often use lightweight panels on a light metal frame over exterior insulation. It is popular in Europe and is often presented as state-of-the-art even though it was invented in the early 60's when I was in school. 

2) Backside-ventilated/Open rainscreen - This system is similar to the PER but doesn't deliberately try to equalize air pressure. It is unsealed at the top, bottom and sides. joints in the cladding are open so that water can enter and drain. This appears to be the system that ehancock was origianlly trying to build and would explain the purpose of the horizontal panel cuts he described although I don’t understand how the smaller panels would actually be detailed. 

3) Simple-rainscreen/Drainage-cavity (too many names and variations to list) – This wall system consists of closed water-resistant cladding over an air space. The design community is divided about whether it is a true rainscreen, not that it matters. This appears to be what ehancock’s professor was thinking of when he recommended sealing the rainscreen panels (I think). Common residential examples would be siding over vertical strapping or a brick veneer cavity wall system. This system is recommended where precipitation is under 60 in/yr.

4) Drainage-plane - This wall system has a thin underlayment between cladding and sheathing that has a drainage capability. Few designers consider it a rainscreen although underlayment manufacturers have latched onto the term. This system is recommended where precipitation is under 50 in/yr.

Selected from: https://forums.jlconline.com/forums/forum/jlc-online-expert-forums/exterior-details/28898-fiber-cement-panel-rainscreen/page2