Having your home insulated is one of the primary requirements when you build a house; this is especially true for the regions with extreme weather condition. A good insulation not only regulates the temperature of your home, but also helps you to cut down substantially on your energy bills. This becomes possible because a good insulation decreases the need of cooling or heating appliances. There are many different kinds of insulation solutions available in the market, however, it is wise to compare different insulations techniques and go for one which is cost-effective, environment friendly, and non-toxic to human health. When all these aspects are considered it is seen that only cellulose insulation is the one which can meet all the above criteria. For obvious reasons, cellulose based insulations are gaining more and more popularity. Here is all the information on cellulose insulations that you may be interested to know.
Cellulose insulation is a type of building material that is used to insulate commercial structures and homes. It is basically a loose-fill product and is made primarily from shredded newspapers, though some versions also use straws or cardboards.
Types of Cellulose Insulation
There are 4 broad varieties of cellulose insulation available. The most common and widely used variety is loose-fill cellulose and is a dry product. Then there are sprayed versions, which are quite similar to spray foam; these are made from shredded paper that has been mixed with adhesives and water. The third category is called stabilized cellulose; this type is moistened with water to make it expand slightly. Thus, a small quantity of material fills up a larger space. The fourth one is newer dust-free cellulose; this type is treated with oil in order to prevent any dust to be produced during installation.
Though there may be some minor disadvantages of cellulose insulation, however, the advantages outshine any disadvantages or drawbacks that it may have.

Here are some of the advantages of using cellulose insulation:
•    As per Energy Savers, cellulose insulation has a higher R-Value as compared to other usual insulation methods. The R-Value for cellulose insulation is 3.6-4.3 per inch, whereas the R-Value for fibreglass batts ranges from 2-3 per inch.
•    When it comes to foam based insulations, they have a slightly higher R-Value than cellulose insulations, but in the long run, cellulose insulation prove to be more cost effective than foam based insulations.
•     Cellulose insulation. types only use recyclable materials for the major part. That makes it an environment-friendly choice too. Cellulose is biodegradable and thus doesn’t affect the environment in an adverse way, unlike the other traditional methods.  
•    insulation is fire resistant. Naturally, the newspapers that are used in this insulation type are at higher risk of catching fire. Therefore, they are coated with boron during the making process. Boron is a natural inhibitor of fire. Thus you are safer from fire with cellulose insulation in place.
•    As it better conceals both heat and cold, the use of heating and cooling electrical appliances is reduced too and you save substantial amount on your power bills.

More astroturfing?

Exaggerated astroturf at that:

"The R-Value for cellulose insulation is 3.6-4.3 per inch, whereas the R-Value for fibreglass batts ranges from 2-3 per inch."

Uh-huh, yeah, right, R4.3 per inch cellulose, and those R15 (or R11, or R13) batts designed for 2x4 construction are mis-labled, since they're at most R10.5...

What about the negatives? I have heard of issues with moisture. Is this a concern? What other concerns are there?

Cellulose is often a solution to vapor diffusion moisture due to it's ability to buffer large amounts of moisture without damage, drawing moisture from minor leakage or vapor diffusion away from structural wood. But if soaked in a deluge it takes too long to dry, do it usually must be replaced in the event of floods, severe roof leaks, or plumbing leaks.

Being more air-retardent than low-density fiber, structures insulated with cellulose are less prone to damage from air transported moisture too (but not to the same extent as expanding spray foams- it's an ai-retarder, not an air-barrier.)

Some manufacturers still use sulfated fire retardents (banned in some countries, but not USA) for dry blown, which is corrosive to metals (and stinks) when wet, but wet-sprayed cellulose, and better dry-blown products only borate based fire retardents.

Most cellulose insulation ends up in a landfill. Its environmental qualities include the use of renewable resources and naturally the energy saved when using any insulation. The fact that water and air are often used to apply the product, versus various accelerants having questionable impact on the environment, is another point in its favor.

As for R-value per inch; the clear winner for most practical applications (especially retrofit) is high-density 2lb. foam.

I'm gonna add some insulation to my home in Minnesota. Looking for input on which way to go.

Minnesota
3000 sq ft
3 levels, with 3rd level being loft bedroom, high vaulted ceilings.
20+ years old

minimal existing cellulose now, should i just add to it or pull old stuff out and add new?

is cellulose the best way to go bang for buck or spray fiber products?

how tough is it to insulated the vaulted areas w/ blown insulation?

is this a DIY project? what kind of prep work is required? any tips? I noticed big box's rent or give you the machines with purchase of product.

R value per inch is one thing, R value per dollar is another, eh? ;-)

Applied in the correct stackup any insulation can avoid the landfill for at least a century, but even 2lb foam can end up in the landfill if improperly done. To be sure air-impermeable/water-vapor semi-permeable foam is far less sensitive to moisture, but it can either protect or destroy structural wood in a building by where & how it is applied.