Radiant Barrier/ insullation Delima

[Pooka]

Hello Folks!
I am researching ways to improve our energy efficiency here and have decided that the most immediate need with the Texas heat is more insulation. I should mention that our A/C Ducts run through our attic which is about 4 feet high... in other words the temperature of our air is raised considerably by the outside heat.

To alleviate some of this I plan to increase the attic insulation to anywhere from R38 to R49 and in addition I'd like to go with a radiant barrier. Here is where I'm torn. The foil variety will give in (in theory that is) a 97% reflectivity witch is excellent, however it can't be installed in an existing home all the way to the roof line and so you loose some of that 97% which matters considering the cost if greater than the spray on "paint" variety. The Heat-Block 75 seems to be the highest functioning of the spray on varieties it has a reflectivity of 75%, but because you can use a long narrow sprayer it will cover completely and all 75% will be retained. At least this is what I've been told.

As for insulation I wanted cellulose (the recycled variety... just trying to go as green as possible) but I have found that the cellulose contains Formaldehyde as a fire retardant and I'm really not keen on the idea of that being in our house especially being that I am very allergic to it... couple that with the fact that cellulose can mold and even with the retardants burn...and fiberglass is looking more appealing to me. There is a type called Jet Stream 73.3 which is not as irritating as the shaved fiberglass... and it is non-combustible, doesn't support microbial growth and won't rot mildew or deteriorate. So I'm thinking this is what we'll go with... and I'm leaning more toward the R49 simply because we have an old 10SEER A/C and it is MUCH cheaper to insulate than it is to replace that unit(which will be replace for a small service fee by our home warranty when it finally gives up the ghost).

What is your experience with any of these products or types of products? I'd like to have some feedback from people who actually have them before I write a check. The ultimate goal is to reduce our bill and make our home more comfortable at the same time.