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Old 11-05-2015, 12:29 PM
 
Location: California
6,416 posts, read 7,624,339 times
Reputation: 13957

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We just moved into our home and the flexible ducts under the house need to be replaced. The salesman said it would be best to have new ducts through the attic and have the vents high on the wall. Currently, the vents are at floor level, so does anyone know whether the hot air is drawn into the room from the top as well as from the bottom of the wall?
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Old 11-05-2015, 12:49 PM
 
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Hot air rises so having the heating vents at a low level will encourage circulation.

But if it is just the ducts that need replacing why would you replace all the vents and re-engineer the system? Sounds to me like someone is just trying to milk the job for every dollar they can get
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Old 11-05-2015, 02:23 PM
 
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Quote:
Originally Posted by MidValleyDad View Post
But if it is just the ducts that need replacing why would you replace all the vents and re-engineer the system? Sounds to me like someone is just trying to milk the job for every dollar they can get
Or there's Vastly more to the story.. like ductwork that needs to be replaced regardless and having access to a well insulated attic space vs an uninstalled crawl space.

No need to make assumptions when the OP didn't provide details.
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Old 11-05-2015, 04:03 PM
 
Location: California
6,416 posts, read 7,624,339 times
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Thank you for replies.

Yes, there is more to the story but I'm not sure I understand everything they are telling me. We had a great inspector prior to closing who photographed the crawl space issues. The insulation had been eaten away leaving holes in the ducts, as I understand it. The salesman thought it would be easier to use the attic to run new metal ducts as the space under the house is very tight but I don't know whether it is better to insist on using the existing system or let him run it through the attic. He said it was more efficient as the heat is absorbed by the cool air.
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Old 11-05-2015, 04:29 PM
 
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Heat rises. Heat added to a crawl space means warmer floors, and very little "lost" heat escapes around the perimeter of the house. In summer, any central air isn't fighting against hot attic temperatures. Attic runs are more common in dirt cheap and retrofits.

If there is a problem with holes in flexducts, chances are good there are rodent issues. You don't ignore rodent issues by running ducts in the attic and hoping they will go away. Rodents ALSO chew into electrical wiring and create shorts and situations that burn houses down.

Tell the salesman to stick to sales.
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Old 11-05-2015, 05:09 PM
 
Location: Johns Creek, GA
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You're getting raked over the coals!

"Fix" the rodent problem- "repair" the HVAC problem!
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Old 11-05-2015, 05:29 PM
 
621 posts, read 1,114,464 times
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Floor level grills under the window is the preferred location when heating is the primary function. Interior floor supply grills are from a converted gravity heater and should be abandoned/removed or converted to returns with new supplies installed. Upper level grills should be positioned on a wall opposite of glass/pointing towards and favor a cooling function.

The crawl space is tight which rules out metal ductwork. It will get crushed by any worker in the crawl space where flex duct will likely spring back into shape. Rodent proof the crawl space to avoid their return prior to the project.

You're in California which requires duct leakage testing for any project similar to what you're describing unless you're using a shade tree outfit. Make sure they comply with the testing requirement.
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Old 11-05-2015, 06:45 PM
 
Location: California
6,416 posts, read 7,624,339 times
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We were told that by using the metal ducts we will never again have rodents eat our duct work. The rodents were taken care of but the prior owner did nothing for the ducts. That and a few other issues is why I had to argue so hard to have the inspections I wanted.

The salesman said to put a piece of duct tape over the vent and leave it there for an hour or so to see how much fiberglass is in the air coming from the existing vents.

BTUHACK, are you saying the since we have A/C and heater the ducts should be replaced and brought down from the attic?

I don't recall seeing any leak testing on their quote but I will go back to verify that.

Thanks for you time and thoughts.
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Old 11-09-2015, 08:01 PM
 
621 posts, read 1,114,464 times
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Quote:
Originally Posted by Heidi60 View Post
are you saying the since we have A/C and heater the ducts should be replaced and brought down from the attic?
I'm just telling you what usually works best. I'm having trouble following what you have and what your objectives are. FWIW, aluminum is metal and hardly rodent proof.
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Old 11-10-2015, 09:11 AM
 
1,399 posts, read 1,788,131 times
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Can someone please explain to me why ducts are in front of windows? This is the greatest point of heat loss in the house right?
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