ADDING TO EXISTING ATTIC INSULATION, INSTALLING BAFFLES,
AND DECIDING TO DO-IT-YOURSELF OR HIRING CONTRACTOR
QUESTION FROM CENTRAL FALLS, RI:
I have in my attic old r-19 that is face down flat. My studs are 24 on center
Should I replace it with the r-30 or just lay over it another r-19
ANSWER FROM THE INSULATION DOCTOR:
There's no need to remove the existing insulation. However, prior to installing more insulation you should install air baffles at the eaves, commonly referred to as proper vents -- one in each rafter space.
If you are a "do-it-yourselfer" you can obtain unfaced R-19 blanket or R-30 which is a true 24" on-center thus covering the top of the trusses. However, you may find cost-wise more efficient to have a contractor come in and install the proper vents and blown-in insulation at about the same price as you would spend for the retail cost of purchasing the blanket insulation and doing it yourself.
The other option is that many of the large builder supply stores, such as Home Depot and Lowes, will rent you an insulation blowing machine if you purchase the loose-fill blown-in insulation from them. To avoid using too many bags of material I would recommend that you mark the attic at the depth you want to install either with paint markers, rulers, or strings. The reason for this procedure is that when you are in the attic your depth perception of 6", 8" or 10" will be distorted and you may end up using more bags than necessary to complete the job.