sealing A/C ducts & boots by registers

am looking to take off all registers inside house and use mastic to seal all the boots. is it as simple a job as just covering hand with latex glove and smearing a generous amount into the area where the boot meets the sheetmetal duct?
any info or corrections are appreciated. home depot sells the mastic so I know at least where to get it
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What's a boot?
And why are we doing this?
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DerbyDad03 wrote:

end of runs of the insulated sheetmetal, in the attic, terminate in a boot which attaches to the registers

for the purpose of sealing some small leaks where warm air from attic is mixed into the cooled air flowing from the register. this should improve performance a little bit and would also stop a couple registers from dripping condensate (inside temp is 77F but air from register is coming in at 59-61 and a couple leaky boots are condensing on the outer surface)
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mike wrote:

In my experience, boots are often installed by cutting a hole about 1" larger than the boot in the floor / ceiling, then stuffing the boot in with minimal attachment. Consequently, there if often a lot of air leaking between the boot and the ceiling / floor. First, if the boot seem loose, do what you can to secure it. Then caulk or seal the gap with whatever you can (latex caulk, foam caulk, duct mastic, etc.). If you think that the joint between the boot and the duct is also leaking (I have not seen this to be as big of an issue), seal that too. If you can get to the outside of the duct do it on the outside. If you use mastic, I would get a small paint brush -- metal edges can be quite sharp and would easily cut through a latex glove. Insulate the outside of the boot if it isn't already.
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- DerbyDad03 wrote:
- - What's a boot?
- end of runs of the insulated sheetmetal, in the attic, terminate in a boot which attaches to the registers
Insulated sheetmetal? Ducts in an attic? Boots and registers?
Man, I need a new house!
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That may or may not help. Do you know that you have leaks there that need sealing?
What's the R Value of your ducts? Lowes sells insulated ducts that are likely double the R Value of yours. So replace them.
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ValveJob wrote:

yes, a few registers are sucking in warm air. was there anything in my description what was wrong? I mean to the process of applying mastic?

the house is rather large so not quite a simple job to pull out the existing and inject new sheetmetal into the attic. the ones I now have are rather sturdy, made from galvanized sheetmetal and appear very well wrapped, no moisture is detected and no temp variations from the few times I've crawled the length of the "pipes"
for now, just wanted to seal the registers & boots
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Then I'd say your solution is absolutely correct. We know it should have been liberally applied when the boots were first installed, but your method should work to fix what wasn't installed properly or deteriorated over time.
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Just make sure you clean around the area that you want to reseal so the tape and mastic will seal properly.
-- Moe Jones HVAC Service Technician Energy Equalizers Inc. Houston, Texas www.EnergyEqualizers.com
looking to take off all registers inside house and use mastic to seal all the <BR>boots. is it as simple a job as just covering hand with latex glove and smearing a <BR>generous amount into the area where the boot meets the sheetmetal duct?<BR><BR>any info or corrections are appreciated. home depot sells the mastic so I know at <BR>least where to get it<BR><BR></BLOCKQUOTE></BODY></HTML>
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1. It may be easier to use caulk if you are sealing small cracks. 2. Instead of applying the mastic to a gloved hand, try a cheap paint brush. It's better than snagging your hand on a sheet metal meat hook. 3. Make sure you seal the return system.

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Use a cheap 2" brush that has fairly stiff bristles. If there is an a/c supply house near you, see if they will sell you a gallon of duct sealer. The stuff HD and Lowes carry is not as good as what is used in the trade, and they get about as much or a small container(quart?) as a gallon costs at the supply house. There are several brands, all about the same, that wholesale for about $11-14/gal, though they may charge a homeowner more, assuming they will sell it to you at all. They will also most likely have the brushes too. BTW, you are probably thinking the stuff is thicker than it really is. It is about the same consistancy as drywall mud. Good luck Larry
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