Insulating with Prodex & Fiberglass
ProudTexan
| Posted in Energy Efficiency and Durability on
Anyone familiar with using Prodex products to insulate a North Texas home (16×52 cabin) in combination with fiberglass insulation?
2×4 walls with layer of sheathing and smart siding (prebuilt cabin – no exterior wrap or vapor barrier)
Ceiling can be any thickness
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Replies
It's a scam. It doesn't really deliver r22. It's 3/8 of an inch thick. Maybe R1 in reality.
I will rely on the fiberglass insulation R13 - R15 for R-value. I am interested to know if the Prodex would be good to add (either inside the wall against the exterior sheathing or outside the fiberglass under the drywall) since there is no wrap or vapor barrier installed on the outside sheathing. Has anyone researched using the 2 products together for this purpose?
Are you heating-dominant or cooling dominant? You want the vapor barrier on the side that's normally warmer, which in heating-dominant is the inside, in cooling-dominant the outside. If you're heating-dominant I'd just use a faced fiberglass insulation.
Any housewrap has to go outside the sheathing, there's no way to retrofit it without taking the siding off.
If you're not sure if you're heating-dominant, go to this document:
https://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/County%20Level%20Design%20Temperature%20Reference%20Guide%20-%202015-06-24.pdf
Look up your county, and look at the column "HDD/CDD ratio." If it's over 1.0 you're heating dominant.
Texas is definitely cooling-dominant. My location is 0.4 as shown in the energystar link provided. It sounds like I should simply insulate and install a vapor barrier if new siding is installed in the future.
This leads me to my next question...
Is it acceptable to install vapor barrier directly over the existing LP siding and sheathing and then install new siding? In other words, sheathing directly in contact with LP siding, then vapor barrier (over the LP) and then install "New" siding (possibly pine shiplap). They are all directly in contact with each other which may or may not be an issue. I am researching the best way to proceed and appreciate your input.