do I need to insulate new bathroom exhaust fan ducting that runs in attic?


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Old 02-10-14, 08:46 AM
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do I need to insulate new bathroom exhaust fan ducting that runs in attic?

I'm installing a bathroom ceiling exhaust fan. The ducting will run in the attic and exhaust through a roof vent. The length of the ducting will be about 20 feet. I plan to use 6 inch dia. galvanized rigid ductwork. The attic is vented via soffit, side vents and ridge vent. I live in northern Va, and in winter it is on average around 35 deg F. Do I need to insulate the ducting in the attic?
 
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Old 02-10-14, 09:18 AM
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At 35° it will be well below the condensation temperature for that humid air being exhausted. Even with insulation you need to be sure the ducts are sealed and tipped to drain somewhere. Going up, I'm not sure where that is.

Also, be sure to add a delayed off switch that keeps the fan running for a preset amount of time. This helps to dry out excess moisture in the bathroom and dry out any condensation in the duct.

Bud
 
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Old 02-10-14, 10:49 AM
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Thank you for the response Bud.
 
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Old 02-11-14, 06:13 AM
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Bud, will insulation be effective if the duct exhausts via a roof vent that has a cover to keep elements out but no damper. The fan has a damper. It would seem to me cold air would migrate through the duct when the bathroom exhaust fan is off so the inside of the duct would be the same temperature as the attic just as if the ducting were uninsulated.
 
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Old 02-11-14, 06:28 AM
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Im in VA and my bath vents are not insulated. I have never had an issue
 
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Old 02-11-14, 07:06 AM
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It is always hard for me to judge temperature relate issues away from my local climate. Take my advice with that in mind and consider Airman's who lives in your state .

The delay timer is always a good idea as it reduces moisture in the home which becomes a problem as you air seal and insulate. And as stated it will help dry any condensation if it forms.

Bud
 
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Old 02-11-14, 07:33 AM
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Bud it could be ive never had an issue because I run the fan so long. I don't know the real answer but insulating them isnt going to hurt.
 
 

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