If an attic is not accessible, you should consider using an experienced energy auditor, or insulation contractor to assess your attic insulation level(s). An auditor, or contractor using special diagnostic equipment, may be able to determine existing insulation levels and opportunities for additional energy savings. In some cases, the only way to gain access to the attic and determine insulation levels is to cut into the attic from the inside or the outside.
For more information, contact your local Extension office. Visit the eXtension web site to find Local Extension offices near you.