# Insulation type needed if using RedGard waterproofing?



## ccarlisle (Jul 2, 2008)

Well, the theory goes that a waterproofing membrane such as RedGard will, if installed properly, _prevent_ any vapour from diffusing across the cbu and into the wall structure where, in cold months, it will condense to water. As such, the problem 'goes away' in that no vapour=no problem...and therefore no vapour retarder behind the cbu is needed. Insulation yes - but no vapour retarder; I subscribe to that theory so I'd say either remove the little bit of faced insulation you have, or remove the paper facing of it...

But since you're already there, why not upgrade to Roxul mineral wool, if buying a bag isn't too much for you to use? If so, then buy a small bag of pink fibreglass insulation and be done. 

Not too sure where you're located but this should hold up pretty well anywhere...


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## Bud Cline (Mar 12, 2006)

I would agree with the above but take it one step forward and suggest you use Denshield instead of Hardbacker. Denshield offers a protective coating and all that has to be addressed then is the seams and fastener penetrations. Denshield is also much much much easier to work with and the fasteners will be easy to "set-the-heads".


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## bigphil (Sep 26, 2011)

Thank you both for the replies. I'm in Seattle btw. well...I already purchased the hardiebacker and my buddy had a bag of r15 yellow fiberglass batts (freebie) that fit perfect so thats what I used. I suppose I'll just keep the paper on the insulation then because I already have some cbu up there and its a pain to take it down. I'll be sure to apply the RedGard properly to be sure its 100% waterproof (i'll probably throw 3 layers on instead of two). thanks again!


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## Bud Cline (Mar 12, 2006)

Hardibacker will easily require a minimum of three applications.


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