trojnstealth & comfort service,

starting your own thread would be less confusing to those of us trying to
reply. same for comfortservice. maybe mods will do this for y'all...
also including location helps as does location/type of duct system.
thanks comfort service for including this info. but what is insulation type?

blown cellulose insulation, recessed lighting are contributing to the 'dust'.

unless your recessed lights are ICAT (insulation contact air tight)
the hvac system pulls in that fine ground newspaper dust that is
treated with borate.
you can tell which light you have two ways.
from inside, removing bulb & carefully reading sticker inside of can.
Note: read for what is air tight & what achieves air tight when
'used with the following trim/inserts'.
Halo is a common brand made by cooper lighting.
if the can needs inserts, trims the sticker will have red circle around
details. if its ICAT the circle will be orange.

option two is to go into attic, move insulation back from housing
& look for light from inside house. (cut lights on prior to getting in attic btw!)

when the hvac system runs it forces air into the house, so leaks like
can lights, oversized cuts at bath fans, stove vent fans & even the
cut where the supply box enters the living space are all entries for
cellulose dust.

comfort service, in addition to the info above,
return air leaks need to be sealed. r/a leaks contributes to
higher RH.
sealant...Mastic. paint on mastic for duct take offs @ plenum, &
acessible areas, mastic tape for plenum to equipment connections.
also removing the supply grills & using Hardcase brand #1402 tape
in method in attached picture works well.
I've tried other brands of mastic tape, but this is the one that
holds strongly, tightly & for a long time.

blower door testing & duct testing would be the best place to start
for both of you.
Resnet does duct testing as a standard, BPI may require requesting this service.

best of luck to both of you.

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