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Insulating square ducts in crawlspace

2K views 4 replies 2 participants last post by  nova_ducts 
#1 ·
Hi all, new to the forum but hope someone can offer assistance. Background:

  • 1940s house in Northern VA
  • Vented crawlspace approx 30' x 20'
While installing some cable in the crawlspace recently, I noticed a few issues with the ducts - photos attached.

The ducts have been (more or less) sealed with mastic, but they are uninsulated and there is a little mold/mildew on the joists. I'm wondering whether I can/should insulate these ducts and if so how? I can wrap duct insulation around some of the tubular supplies, but the square ducts completely fill the space between joists.

Thanks in advance for any assistance.
 

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#5 ·
Okay, just picked up some of these 2" x 4' x 8' foam boards. Unfortunately no spike fasteners available - the salesperson recommended just using liquid nails or regular nails with washers to secure the foam to the joists. Is there a risk of condensation pooling on top of the foam board if it's glued to the bottom of the joists and effectively touching the duct?

Thanks again.
 

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