# Looking for an alternative to insulweb for a small job



## bvz (Mar 17, 2008)

Hi,

I just finished ripping out the drywall on the inside of an exterior wall in my house. We have been having issues with condensation forming on the inside of the wall when it gets cold. I had had my house insulated using blown in cellulose about 10 years ago but clearly they missed some cavities. Wherever they missed a spot due to weird cross bracing (and it turns out there were a fair few spots) we have been getting mildew.

Now that I have pulled off the drywall, I intend to do a "cross hatch" wall (or mooney wall). I am hoping the extra insulation (and, really, just having any insulation at all in the mildewy sections) will stop this condensation problem.

But before I do, it turns out that the existing cellulose (where it existed) has stayed in place quite nicely during my demo. I'd like to just put up some insulweb type netting to hold it in place (and then add more insulation in the empty cavities and those few cavities where the existing cellulose does not come completely to the top). 

I want to do this BEFORE adding the cross hatching since the installation of the new framing members will no doubtedly disturb the exisiting insulation to the point that it will fall out and I will have to start from scratch. Once it is properly netted, I will add the cross hatched framing, and then most likely insulate within these new cavities using some rigid foam insulation.



So, my questions:

What kind of netting (or material) can I use to hold the existing insulation in place? Insulweb is what I keep seeing all over the internet, but I cannot seem to find ANY local stores that stock it. Not the smaller lumber yards in my area (Oakland, CA) nor any of the big box stores (Home Depot or Lowes).

Is there someplace I can source it around here?

Is there some other material that is safe to use inside my walls? I saw a post somewhere that suggested using landscaping fabric. Is it ok to have that in the walls?

Or should I try to carefully attach the new framing with screws (instead of nails) and hope that the vibrations don't disturb the existing insulation too much and then use the rigid foam as a barrier against which I can then do my little bit of additional dense packing?

Or should I just forget about saving the existing insulation (it covers about 75 - 80% of the cavities) put up the new framing, and then try to blow in some dense pack. My biggest concern with this methid is that I may not be able to get my hands on a blower that is capable of the 3.5-4 ilbs per square inch. This is the primary reason I am considering rigid foam for the additional thickness created by the cross hatching/mooney wall.

All suggestions greatly appreciated!

b


----------



## Windows on Wash (Aug 30, 2011)

What does the exterior of the home consist of? What surface was the condensation and mildew on? 

What are the humidity levels in the home like? 

Membrain is a good option to hold back the insulation and control moisture. You will need to find and insulation supply house. I wouldn't use landscape fabric either. You can get the netting or the membrain from the supply house.


----------



## bvz (Mar 17, 2008)

Windows on Wash said:


> What does the exterior of the home consist of? What surface was the condensation and mildew on?
> 
> What are the humidity levels in the home like?
> 
> Membrain is a good option to hold back the insulation and control moisture. You will need to find and insulation supply house. I wouldn't use landscape fabric either. You can get the netting or the membrain from the supply house.


Thanks for the quick reply.

My house is stucco on the outside and the mildew (or mold?) was on the paint on top of the drywall. I cut a bit of it out (wearing a mold-rated dust mask and after emptying and sealing off the room) and saw that it did not extend even to the paper of the drywall. I then proceeded to cut away all the drywall around the mold/mildew and dispose of it. After that, I cut away the remaining drywall of the two outside walls of the room. The mildew/mold is, I am pretty sure, the result of two people breathing all night long (generating moisture) and us not heating the bedroom combined with cheap, flat paint (i.e. not semigloss or even eggshell). It quite frequently gets down to the high 50's in there. Every morning the windows are completely covered in condensation (and so I suspect the un-insulated parts of the drywall were as well, though I never saw it myself). I intend to get it properly insulated as well as set up some electric heat with a thermostat to make sure it never gets that cold again.

I will check out Membrain. It has been difficult to find an insulation supply house around here (that I can tell). Being a DIY homeowner I rarely have to go beyond the typical big box stores. But I will give it another go. Thanks!


----------



## Windows on Wash (Aug 30, 2011)

Sounds to me just like you described. You had some uninsulated spots and they were able to drop in temperature enough that the interior moisture formed condensation. 

Do you have any issues with the stucco on the exterior? Stucco tends to leak and moisture in a cellulose wall (or any wall for that matter) can be problematic. 

I am guessing that the flashing and water management details on the exterior are good?


----------



## Gary in WA (Mar 11, 2009)

IMHO, using a polyamide film (MemBrain) in the middle of your wall is counter-productive. Cellulose is hygroscopic (moisture spreads easily) from fiber to fiber. Why add a film to stop/confine any moisture that is wicking it over a broad area (new and old cellulose) to slowly dry. Esp. with an exterior water leak, it would wet the framing that much faster/more before showing on the plaster/drywall. You don't need/want a vapor retarder in your *Climate Zone 3*, or *one with cellulose*, and not in the *middle *of the wall; http://www.nationalfiber.com/docs/H...seInsulationinSuperInsulatedBuildings0913.pdf

http://www.buildingscience.com/docu...heet-310-vapor-control-layer-recommendations/

Why foam board rather than full cellulose? Spritz with water to hold the existing, two days later as you work on the framing, it should be dry.

Gary


----------



## Gary in WA (Mar 11, 2009)

Are you still around, hate to see you leave with bad info... hello... hello.

Gary


----------



## bvz (Mar 17, 2008)

Wow. Thanks for the additional info! Apparently my settings are not set to notify me of additional comments (Windows on Wash kindly pm'd me with a notification of these comments and with some additional info).

I won't be using the membrain as you suggest. I'll stick to the insulweb (which I still cannot find and emailing the manufacturer hasn't gotten any response yet either). But I have also been a bit busy so I won't really be able to put any effort into finding it till early next week.

I thought I would use foam board for the simple reason that whenever I read about rented blowers I seem to read that they do not put out enough power to properly dense pack. Foam board seemed like the easiest alternative for me. Once I install the additional framing it should be easy to cut long, straight pieces of it to fit between the new sections of framing. (It will be a bit more work to back-fill the exiting, un-insulated cavities but, as I mentioned, I'm not sure I can dense pack myself).

With regard to wetting the insulation, I'm not sure I trust myself to do it correctly (i.e. either too much or too little water) and then have problems where it either falls out during construction or is still wet somewhere when I seal the wall up with drywall.

As I write this, I have come up with another idea...

I will use the landscaping fabric instead of insulweb to hold the existing dense pack in place. Then, as I install the framing, I will first cut away the landscaping fabric from where the framing goes (I will cut away just enough to install each framing member, before moving on the the next). Once I start installing the rigid foam, I will similarly pull the landscaping fabric out from behind each one. The foam board will hold the dense pack in place.

No contractor worth their salt would ever do something as bone headedly inefficient as this, but I have more time than experience and this seems like a more foolproof way of making sure my existing insulation doesn't fall out without having to scour the ends of the earth for insulweb. Also: much cheaper.

Thanks again for all your help! (Also, I will try to update my settings so that I am notified of additional posts)


----------



## Windows on Wash (Aug 30, 2011)

http://jrproductsinc.com/shop/pc/viewCategories.asp?idCategory=30


----------



## bvz (Mar 17, 2008)

Thanks for the link! Ordering some tonight.


----------

