Replies

1. 
   Richard Beyer | Oct 22, 2014 09:33pm | #1

   Tough question since no one here knows if you already have water and mold issues. My comment is assuming your installing these products over your interior exposed walls. If you do you first need to manage the water or moisture problem. The foam itself will not cause mold, but the foam has to be covered by a fire retardant barrier per code. This means 1/2" drywall or intumescent paint applied over the foam at the manufacturers mil thickness. That is unless the area is always unoccupied and no mechanicals are in the space. By the sound of it you need to follow code.

   See... https://www.greenbuildingadvisor.com/blogs/dept/musings/thermal-barriers-and-ignition-barriers-spray-foam

   http://www.energyvanguard.com/blog-building-science-HERS-BPI/bid/72240/Does-Your-Spray-Foam-Insulation-Need-a-Thermal-or-Ignition-Barrier

   Also keep in mind... VENTILATION... See... https://www.greenbuildingadvisor.com/blogs/dept/building-science/spray-foam-insulated-homes-need-ventilation#comment-77277

2. GBA Editor
   Martin Holladay | Oct 23, 2014 05:34am | #2

   Jeff,
   The method you describe is (informally) called the peanut-brittle variation of the cut-and-cobble method. For more information on this method of insulating walls, see Cut-and-Cobble Insulation.

   As long as you pay attention to airtightness, your method will work fine.

   I have no idea why Richard raised the question of mold, since there is no reason to believe (from your question) that you have a mold problem.

3. 
   Richard Beyer | Oct 23, 2014 09:49am | #3

   Martin, I'm not the one who raised the question.

   "Since there would no longer be fiberglass in that wall, would I have to worry about consensation or mold issues?"

   I addressed the concern. ;)

4. 
   jeffm123 | Oct 23, 2014 05:19pm | #4

   Thanks for your responses. I don't think I phrased my questions in a clear way, but my primary question was "would this work" and my secondary question was "would this lead to problems (like condensation... thus leading to mold)".

   Since this is a fairly new construction (5y old), there aren't any mold or moisture issues right now. I'm working to finish my basement and would like to improve on the R19 fiberglass batts that the walls currently have.

   I appreciate the link Martin, the blog post was very informative. I was worried that this was a problemmatic approach, because I've seen XPS+spray foam recommended in rim joists (as an alternative to spray foam) and I've seen buildingscience.com recommend spraying foam over XPS against a concrete wall, but in the context of an above-grade wall, I haven't come across any information yet.

   It sounds like I won't be introducing many problems, but will still be suffering from thermal bridging, just as I was with the R19 batts. I guess I will continue with the peanut-brittle appraoch for now and look into exterior insulation down the road.

   Thanks again!

5. 
   1ben | Aug 10, 2022 03:16am | #5

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