Duct sealing questions


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Old 07-05-17, 12:33 PM
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Duct sealing questions

My duct work is pretty old. Maybe 20 years. Nothing has ever been sealed and theres an abundance of leaks everywhere. I just sealed all the leaks in the supply trunk I could reach today. My air output increased significantly! Awesome!

My question is, should I do the return trunk too? I held a piece of tp up to suspicious areas and it neither blew nor held in place. I just don't know if I did any harm with the aforementioned sealing and if doing what I can physically get to on the return trunk would hurt my system.

But to be honest I can't believe the increase in airflow. Id say probably a good 30% extra coming out of the vents. I still have the closest trunk to do, although in not sure how leaky that is. I only did the unfinished basement where everything is.

Edit: also ive heard people say take off your ceiling registers and seal that. Can someone explain that a little better? What part am I sealing? Thanks
 
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Old 07-05-17, 01:40 PM
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no expert here but some common sense logic...

You want the air coming our of your AC/Heat to go directly to your registers and not leak out of the ducts or where the registers might attach. That would mean losing your conditioned air. On the return trip to your AC/Heat, you need to be supplying enough CFM of air for the unit to function properly. Having leaks in the return is not critical but you do have to consider that the purpose of the return is to get unconditioned air from the home back to the blower. If you are taking air from the outdoors (or attic, crawlspace or other), then you are probably not helping your yourself. In the summer, you want to taking the hot air from the house and sending it back to the blower to be cooled. If it is leaking, then you aren't drawing air from the places you want to draw it which will result in less than optimal results.

- Peter
 
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Old 07-05-17, 01:46 PM
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Sealing duct in the conditioned space does very little good. But if you think it helped get you 30% more air then you had some huge holes and would help out.
 
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Old 07-05-17, 02:22 PM
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Well all the leaks were in an unfinished basement. There were some significant ones, especially around the whole house humidifier. That might as well been its own supply vent it was leaking so much air.

As for the returns, I don't run the risk of screwing up pressures? I honestly don't know how to test it or what to look for thats why Ive held off. All the returns come through the unfinished basement as well then go into the floors (single story)
 
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Old 07-06-17, 01:19 AM
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Leaks in the ducts, both supply and return (to a lesser degree) will effect the system performance.

Sealing them is cheap and easy and will only improve efficiency.

I've sealed every joint I can get to easily!
 
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Old 07-06-17, 04:39 AM
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Ok thanks. I didn't know leaking return ducts had an efficiency issue at all. Just thought it contributed to dirtier air/filters.
 
 

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