Tape vs. mastic
I’m posting this under both Energy Efficiency and Mechanicals, in the hope of catching more flak.
“Reputable” duct sealers all swear by mastic, but a good “duct tape”, e.g., Nashua 322 or 324a seems adequate to the task at hand. 324a has an application temp from -10 to 200ºF and a max temp of 325ºF. Even 322 is good for a max temp of 200ºF. I hope my ducts aren’t getting that hot.
Certainly one needs to be conscientious in the application of tapes, being sure to cover all the joints and pressing it down all over the joint, but mastic isn’t fool-proof either- I would argue that in all but the most experienced hands, tape is more likely to be effective than mastic, if it lasts.
AND, applying tape while squirming around under a house certainly seems easier than wrassling a tub of mastic. I’m visualizing using mastic covered gloves to drag my body through the crawl space, getting mastic on the plastic, getting mastic on my clothes, forgetting and wiping sweat off my face, adjusting my glasses, brushing my hair out of my eyes… you get the picture…
So, what does the community have to say on the subject?
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