I live in a townhome that was built around 1980. All ductwork and insulation is original as far as I know. I have terrible sinus allergies in this place. For years I just dealt with it, blowing my nose often. It is only on a recent trip to an ear nose and throat doctor that I discovered my allergies could do long term damage to my ears.

A couple years ago I removed all the carpet and replaced it with laminate flooring, but while that helped a little, it did not solve the problem. I then had the ducts cleaned but again this did not help. Last week a consultant from a large hvac company came out to quote me on some work.
He recommended replacing the ducts in the attic, taking out all the old insulation and replacing it with new insulation. He said since the ducts were so old, it was likely that they had leaks and all the crap in the attic including the insulation was being blown into the house. There is also old insulation wrapped around all the ducts that he said was probably getting into the ducts and blown into the house. I'm no expert but what he said all seems to make sense.

Now for the downstairs. The dstairs ducts cannot be accessed. He recommended doing an aeroseal job on them to seal them up and then cleaning the ducts ( or cleaning and then aeroseal, I cant remember the order). I do not know what it looks like around the ducts dstairs, but I would guess it is just as nasty as what it looks like in the attic. My concern is that the aeroseal site says it seals up to 80% of leaks. My thinking is that if there is a lot of nasty stuff around the down stairs ducts, it can still get into the ducts through the 20% that remains unsealed after the ducts have been cleaned.

So all that was recommended was upstairs: replace upstairs ducts, remove old insulation and add new insulation

dstairs: aeroseal and clean ducts

The cost is hefty. I will say, the last 2 days I have not been running my central heat at all my allergies have improved quite a bit, so it does seem like I'm allergic to something coming out of the ducts. I will probably turn the central heat back on soon just to confirm that. My question is, does doing this sound like a good plan? Do you think aerosealing and cleaning the down stairs ducts will improve my situation, even if it only seals 80% of the leaks?

I have already done everything in my power to eliminate dust and mold inside the house. I already clean every day, i've removed all old blinds, curtains are brand new or have just been washed etc. Thanks