What are Attic Insulation "R" Values?

If you believe your home is under-insulated, you can perform an easy insulation inspection to determine your insulation requirements. Having the proper amount of insulation in your attic could help you keep comfortable temperatures in your house and help you prevent major problems like ice dams in the wintertime. Plus you can even save money on your energy bills.

Levels of insulation are specified by R-value. This is a measure of the ability of the insulation to resist heat flow. The greater the R-value, the better the insulation's thermal performance. The suggested level for most household attics is about 10 to 14 inches (insulate to R-38), depending on the type of insulation.

The "R" refers to resistance to heat flow. The greater the R-value, the greater insulating resistance and power there is to heat flow.

What's the Proper Amount of Insulation to Install?
There are various factors that will depend how much insulation you should use for your home. Some include:

  • The age of your home: If your home is over 10 years old, you likely require more insulation. There are various ways of retrofitting a house with mineral wool and fiberglass insulation.
  • Where you live: Various climates require various R-value insulation. You'll require a greater R-value of insulation living in the Northeast than say living in Southern California.

Add the Proper Type of Insulation
When you add extra insulation, you don't need to use the same insulation type that presently exists in your attic. You could add loose fill on top of blankets or fiberglass batts. If using fiberglass over loose fill, ensure it doesn't have foil or paper backing — it must be "unfaced." If choosing to add loose fill, it might be a good idea to hire an expert since the application requires you to use a blowing machine. But, certain home improvement stores provide these machines as rentals.

Regardless of the type of insulation you presently have in your attic, one fast way of determining if you require more is looking across the span of your attic. If you notice the insulation is just below or level with your floor joists, you'll want to add more. If you can't see the floor joists at all, this means the insulation is well above them and you likely have a sufficient amount. It might not be cost-effective to add more. It's essential the insulation is distributed evenly with no low spots; in some cases there's sufficient insulation in the center of the attic, and not enough along the eaves.

Allow Natural Ventilation with an Attic Fan
It may seem odd to add insulation for warmth at first, to then purposely allow cold air to enter your attic through an attic fan and vents. But, as the Environmental Protection Agency (EPA) explains, this combination is the key to an energy-efficient home. Here's the reason: allowing a natural flow of cool, outdoor air in the winter not only ventilates your attic, but also helps to keep it cold, which is essential to reduce the potential for ice damming. Ice dams, which can damage a roof, can occur when snow melts off a roof from a too-warm attic and then re-freezes at the gutters.