Fiberglass batt insulation is the most commonly used insulation in attics. In most situations it does not cover the studs and this is an easy escape route for HEAT LOSS
BLOWN Insulation is usually an easy and inexpensive way of insulating. Although it is not an AIR SEALER it does however fill in the smaller gaps that Fiberglass batting can not. This in turn will help slow the rate of HEAT LOSS.