On Mon, 2 Jul 2007 19:01:33 +0300, "mike" wrote:

ValveJob wrote:
That may or may not help. Do you know that you have leaks there that
need sealing?

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?

What's the R Value of your ducts? Lowes sells insulated ducts that
are likely double the R Value of yours. So replace them.

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

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.