As time goes by, insulation in the attic can settle, resulting in the degradation of insulating property (measured in R-value). To find out if you have enough insulation in your attic, use a yardstick or tape measure to record the depth of the insulation. The Department of Energy recommends insulation for Northern climates to be R-49, Southern climates to be R-38.
The most common insulation materials are fiberglass batts, blown-in cellulose, and blown-in fiberglass. You can find out the relationship between the thickness of materials and the R-values from our insulation materials page.
I would recommend insulate up to R-60 for North climates, and up to R-50 for Southern climates. The difference is just like your attic is having a thick blanket or lightweight blanket. A thicker blanket keeps your house warmer in winter and cooler in summer. Your furnace and air conditioner would run less often. Once you start an insulating job, the additional material and labor costs to achieve higher R-50 or R-60 value are only minimal.
One important reminder – do not forget to seal air leaks before adding more insulation.
Here is also a DIY video to help you check the attic insulation.
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