Closing return during winter

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Old 10-02-20, 07:08 AM
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Closing return during winter

I have a 2 story home with forced hot air as well A/C. A little background.... The system was installed a few years after I bought the place and before that I had hot water heat. There is a 4 foot crawl space with just a gravel floor under the house located about 250 feet from a lake in the northeast US. I get water in the crawl about 2 times a year which could come up to about 4-6 inches.
I have a return vent at the end of 25- 30 foot length of metal duct in the crawl that is sealed around the flooring but still throughs out cold air in the winter months. Can I throw a rug over the top to close off that cold air for the winter?
Thanks.
 
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Old 10-02-20, 08:59 AM
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Does the room the return come from have a heat supply?

Just closing that is sufficient, no air in = no air out!

But it's not going to hurt throwing a rug over!
 
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Old 10-02-20, 12:37 PM
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If air comes out..... it's not a return..... it's a supply line.
Covering it over means no heat coming out when the system is running.

If the duct runs thru an unconditioned area then it will get cold and you will get cold air from that floor register until the duct heats up. It sounds like the duct should have been insulated.
 
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Old 10-02-20, 01:28 PM
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The register is a return, no air comes out from it. It is on the bottom floor in the main living/dining/kitchen area, with at least 5 supply registers. I think it's the only return down stairs.
 
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Old 10-02-20, 01:33 PM
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I think it's the only return down stairs.
Then it is required and I would recommend getting the duct in the crawlspace insulated.
 
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Old 10-02-20, 02:05 PM
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Ya know as I was typing the last post I was thinking the same thing. What is the best insulation type for my application?

Thanks for the help.
 
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Old 10-02-20, 02:39 PM
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Surprisingly enough it's called duct insulation, it slips over the duct like a sock on your foot!
 
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Old 10-02-20, 02:57 PM
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It depends on the type of duct..... round.... square. There are many different types of insulation.
 
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Old 10-02-20, 03:16 PM
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Ok. I think it's square. Just have to get under the house... Bla..... Thanks all.
 
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Old 10-03-20, 08:32 PM
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You will need to do cutting and pasting, er, cutting and taping, of the insulation. With the duct already fastened in place you won't be able to get a sock like tube of insulation pulled around the duct all in one piece.
 
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Old 10-04-20, 10:28 AM
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I'm surprised no one's commented on "water in the crawl about 2 times a year". Isn't that a mold risk?

As for the duct insulation, "Bubble Wrap" is much more user friendly than fiberglass. "Reflectix" is one manufacturer, go with R6. Should be in stock at local supply houses. You must first seal any unsealed duct joints using UL181 tape or mastic, and that's especially important with the standing water in the Crawl Space.

It's quite likely your system's airflow is substandard now, so the advice not to block the return was spot on.
 
 

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