Greenlows recommends R38 on the attic floor as a minimum for North Texas. That's what the US Dept. of Energy recommends as well for this area. Home builders are required to install R30 for new homes but many have began install RValues as high as R49 during this age of energy awareness. We install all types of insulation from the roll out batts to cavity-fills in vertical walls. The fiberglass blow-in is preferred because it does not dust up the foil as much as cellulose and is quicker to install despite being a bit more expensive from a material cost perspective. But cellulose has a better Rvalue per inch, is safer to breathe, is greener from an environmental perspective, yet takes longer to install. It's pretty even performance-wise except that most homes have blown in fiberglass and we don't recommend install cellulose on top of fluffy fiberglass. If it's denser, older fiberglass or old rockwool than installing cellulose is fine.

Insulation Products

Blown-In or "loose-fill" insulation

Owens Corning Fibreglass

Greenfiber Cellulose

Roll on batts for the floor or vertical walls