When you think of your home, the last thing you relate it to is an envelope, right? Take a minute and think of the outside walls, floor and ceiling as the boundaries of this “envelope.” If you seal them with sufficient insulation, you ensure that the conditioned air in your home stays in your home and does not escape (costing you money).
The part of this envelope that has the most impact on your energy use is the ceiling and attic space. Do you have enough attic insulation?
It’s important to visually inspect your existing insulation to determine if you have enough. Insulation should cover the floor and joists of the attic, but most importantly it should be evenly spread throughout the attic with no low spots – even to the eaves, which are often neglected. If you can see the floor joists or if you currently have any insulation rated less than R-30, you might benefit from adding insulation.
Insulation is measured in R-values – the higher the R-value, the better your walls and roof will resist the transfer of heat. Fiberglass insulation rated R-30 is about 8-10 inches thick. When adding insulation, experts suggest a higher R-value, such as R-38 which is about 10-14 inches thick. (More info here and here.)
Choosing the type of insulation to install is a personal preference. Batt insulation can be installed in stages and can be used over loose fill insulation; just make sure the fiberglass batt has no paper or foil backing (it should be "unfaced"). If you choose to add loose fill or blown insulation, consider hiring a professional as it can be a little messy.
Assessing your attic insulation is definitely time (and possibly money) well spent. The attic is one of the easiest places to improve your comfort and the energy efficiency of your home.