Is 30 year old insulation still good?

Thirty-year-old insulation may still provide some thermal resistance, but in most cases it is no longer good by modern standards and should be evaluated for replacement or topping up. Insulation from the mid-1990s was typically R19 in attics, while current Department of Energy code calls for R38 to R60, so it is under-insulated by today's standards. Over 30 years, fiberglass batts can slump, get compressed by storage boxes, become damaged by roof leaks, or be disturbed by pests and electricians running wires, creating gaps and voids that reduce performance. Blown-in insulation settles about 10 to 20 percent over decades, so what started as R19 may now be closer to R15. If your 30-year-old insulation is dry, still fluffy, and evenly distributed, it still has some R-value and you can simply add new insulation on top of it rather than removing it. However, you should replace it if it shows signs of water staining, mold, mildew, rodent droppings, or if it is vermiculite insulation which may contain asbestos. Also, some insulation from the 1970s and early 1980s contained urea-formaldehyde foam that degrades. A home built around 1995 with original fiberglass batts is likely underperforming, costing you 20 to 30 percent more in heating and cooling than a properly insulated home, and adding insulation is one of the highest return investments you can make.