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Insulating Supply Trunk W/ Foil Polyiso

 
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Old 07-04-2019, 09:22 AM   #1
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Insulating Supply Trunk W/ Foil Polyiso


I've got a sheetmetal supply trunk coming off a furnace in a basement/crawlspace and I'm planning to wrap and tape most of it with 3/4" foil faced polyiso.

Should I face the foil in to the duct or out? I understand that radiant barriers (foil face) doesn't work unless you have an air gap between the foil and surface being insulated. Any ideas on how much gap and how to space it out?


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Old 07-04-2019, 09:24 AM   #2
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Re: Insulating Supply Trunk W/ Foil Polyiso


Also... this is in zone 5. Hot humid in the summer and moderately cold winters. The basement buffers the outside temps a bit though.


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Old 07-04-2019, 12:13 PM   #3
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Re: Insulating Supply Trunk W/ Foil Polyiso


out & if in generally an inch - temps you also are buffering is the supply air which can be downright chilly to pretty warm
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Old 07-04-2019, 07:55 PM   #4
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Re: Insulating Supply Trunk W/ Foil Polyiso


The foil always faces away from the duct. Its a vapor barrier.
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Old 07-06-2019, 10:55 PM   #5
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Re: Insulating Supply Trunk W/ Foil Polyiso


I would use an insulation that won't kill everyone in the house from just one 4 x 8 piece smoldering smoke.....

Rock wool foil faced instead.

goop up the tin seams first with duct sealer.

Are your floors/crawl space ceilings insulated now?

Insulate the walls of the basement/crawl space....

Check air loss issues with a door blower first?

Vapour barrier on crawl space floors?

Planning on adding a humidistat controlled ventilator fan for the crawlspace & basement?

Furnace and water heater have combustion air supplies?

Getting the basement/Crawl space air as dry and cool in the summer as possible will save you the most $ during the AC season and shorten the # of days and hours the AC is needed
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