there is no need to remove insulation from the attic.
what you want to do is to seal the areas in the ceiling where this
insulation on the attic floor enters the living space.
what type of insulation is in the attic?
where are your supply grills located? location of return air grills?
do you have recessed lights?
what is attic access..door, hatch, pull down stair?
bath fans in ceiling & stove vent through ceiling?
a blower door test will show you house leakage.
once these areas are sealed...paying special attention to ceiling
penetrations..then insulation particles will stay out of living space.
and allergy symptoms lessen.
replacement of ducts that are acessable is a good idea if they are flex duct.
if they are hard pipe, you would have to compare costs between unwrapping
mastic seal and re-wrapping with R-8 ductwrap to replacing with flex.
for ductwork not acessable, aeroseal is a big cost for a product that only seals
small leakage sites. any areas over3/4- 5/8" are too big for aeroseal to seal.
in some cases the ducts seal better if not cleaned. aeroseal encapsulates
suff in ducts.
sealing returns air tight is also recommended. use only UL 181 code approved
mastic and mastic tape. not foil or duct tapes. my prefrence is Hardcast brand
#1402 mastic tape. strong, seals well and long term seal.
a good plan of action is to start sealing what you know leaks, and work towards
larger areas to seal.
independent (not aeroseal) duct testing should be done prior to any
work ...to pinpoint leakage sites. and then again after work is completed.
remove a supply grill to get an idea of how big the leakage site is
where supply box enters the living space.
I find this to be an important leakage site because it is surrounded
by insulation. I seal with mastic tape, because caulk doesn't stick
to sheetrock dust. also when supply boxes are caulked where the
penetrate, and the grill is installed..the caulk sticks to the grill
& not the hole.
attached is a pic of how I seal these areas. same can be used
for bath fans by removing cover & sealing housing to ceiling.
other pics are open wall in return, with ductboard cut to fit
to seal this area. ductboard would then be mastic sealed in place.
once you have done all the sealing work...upgrade to a media filter
attached is media filter that fits into existing return.
best of luck
The cure of the part should not be attempted without the cure of the whole. ~Plato