Blow-in Cellulose Attic Insulation
I recently had a new air conditioning system installed and several HVAC companies that came over suggested that my attic needed more blown in cellulose insulation. So far, I've had three insulation companies come out and each said I have about 5" of existing insulation and recommended adding an additional 9" to get to R38. My house is 2250 sq.ft that has 27 recessed can lights that need to have heat rings installed around them or cap sheets over them. There is also 88 sq feet of open soffits that need to be capped with polystyrene. I'm getting quotes in the range of $1600 to $2100 for this job. Depending on the brand of cellulose insulation (Green Fiber or United Fiber) they will use 71 or 94 bags of insulation.
Would adding 9" of insulation for $1600 provide a significant energy savings payback in a hot desert climate? Is this a project that should only be done by a licensed, bonded and insured contractor for liability reasons?