Amana Air Command air intake question


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Old 07-25-14, 01:17 PM
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Amana Air Command air intake question

I bought a townhouse in the Spring of 2013, and as the neighbor warned we had trouble with ice dams along the roof edges.

The air intake for the furnace appears to be drawn from a duct that runs from just below the ceiling of the enclosed furnace room (with water heater) up through the second floor and into the middle of the attic. The duct is nearly straight.

My question is doesn't the air intake duct contribute to a warm attic in the winter months (for instance, when the furnace is not running and the room is warm), which in turn contributes to the ice dam problem?

What can I do, if anything, to limit the rise of warm air without reducing the volume of air available to the furnace?

Here's a photo, with the duct on the left, and the two pvc flues from the hot water heater and the furnace.

Thanks.


 
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Old 07-26-14, 07:28 PM
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Is there any reason not to insulate that cavity?

Post a picture from further back.
 
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Old 07-27-14, 05:15 PM
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The photo is from the 'room' where the furnace and water heater are located. It is about 4x5 feet and insulated. The only entrance is through a door in the back of the garage, which is not heated. The only intentional flow of air into that room is through that duct that comes from the unheated attic.

My thought is that the furnace draws air from the attic while running, but when it shuts off and the room is still warm, the heated air in the room flows back into the attic, helping to warm it and contributing to the melting of snow on the roof.

The duct ends about in the middle of the attic. Would it make sense to elbow the duct in the roof and extend it toward the gable vent so it can draw air more directly from outside AND help defeat the flow of warm air up the duct?
 
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Old 07-27-14, 05:24 PM
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I see 2 PVC pipes (possibly combustion air or unrelated pipe and furnace exhaust for a condensing furnace?) and I see what looks like a 10 inch duct for combustion air.

Do you also believe that the chase is being used for fresh air?
 
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Old 07-27-14, 05:37 PM
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From left to right in the photo is the duct to the attic, the exhaust pvc from the hot water heater, the pvc exhaust from the furnace, and duct from the cold air return leading into the central air unit. The last looks wider in the photo than it really is. It's only a 4-5 inch diameter duct.
 
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Old 07-27-14, 05:40 PM
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My only experience is with a newer HE furnace we had installed at our old house which had an intake pvc leading from outside directly to the furnace. Where the pvc was connected in that furnace, this furnace has an open grate.
 
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Old 07-28-14, 07:37 AM
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There is no way there is enough heat rising from that duct to heat your attic space.
 
 

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