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Outdoor Ductwork Insulation

Outdoor Ductwork Insulation

Outdoor Ductwork Insulation

(OP)
In the project I am working on, the existing outdoor air-conditiong (heating and cooling) duct was insulated with 1-1/2" fiberglass and aluminum vapor barrier jacket. However, the insulation at the bottom of the duct always got wet after rain, and already become loose now only after a couple of years new installation.

Has anyone had similar experience or any suggestion what's the best insulation and finish for the outdoor duct?

Thank you very much.  

RE: Outdoor Ductwork Insulation

Depends on how you define "best".  From the sounds of your post, there was no re-covering on the thermal insulation wrap?  IE:  It was the plain foil finish exterior finish?  The normal commercial level is one of two options:

Option 1:  Exterior thermal wrap of min. 2" foil faced duct thermal wrap rigid board insulation, with a re-covering of 0.8mm aluminum sheet, lapped and sealed weatherproof with band clamps on 600mm centres.

Option 2:  Internally lined duct insulation with the sheet metal duct as the outer surface, sealed and waterproofed.

Additional enhancements for institutional/better quality:  Use option 2 with perforated liner on the insulation, and another exterior double wrap of bituminous/asphaltic coating impregnated fibreglass cloth (which could also apply to Option 1, as well).  Then a re-covering with 0.8mm aluminum sheet for heat reflectance.

Yeah, expensive, but depends on how long you want this to last and what the energy losses are.

RE: Outdoor Ductwork Insulation

(OP)
Thanks, GMcD. I don't quite understand what "re-covering" means in Option 1. Is the re-covering aluminum sheet in Option 1 a separate layer from the thermo insulation?

Thanks again for help.

RE: Outdoor Ductwork Insulation

go to armacell.com, look for armatuff

RE: Outdoor Ductwork Insulation

FXDFM:  yes- the re-covering is another sheath over top of the basic thermal wrap insulation.  The light wieght flexible foil finish on the duct wrap is not a weather barrier no matter how well it's installed.  You need to protect it with a real weather shield sheathing.

RE: Outdoor Ductwork Insulation

(OP)
Thanks both of you, GMcD and AbbyNormal.

RE: Outdoor Ductwork Insulation

(OP)
GMcD,

Could you please give me some manufacturers for the Option 2 with exterior enhancement?

Thanks again for help.

RE: Outdoor Ductwork Insulation

There are no "manufacturers"- you have to call your local insulation contractor to do this.  Asphaltic coverings and sheet aluminum are generally available from a variety of suppliers, but if this is specifically an insulation scope, then call your friendly neighborhood insulation contractor/supplier.

RE: Outdoor Ductwork Insulation

(OP)
GMcD, Thanks.

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