How Much Insulation Do I Need in My Attic?

Perhaps the most neglected area of insulating ones home is the attic area. Here are two major misconceptions:

  1. A single roll of extra thick (12″) fiberglass will take care of my insulation.
  2. I don’t live in the far north, so I don’t need as much insulation as someone living in WI or MN.
  3. I live in a warm climate, so attic insulation is not needed.

Addressing, the first misconception, if you live in a northern climate, you will need an R-value of R49.  A 12″ batt of fiberglass will only give you R38. And, if you have gaps between batts where the trusses separate batts, you will have cold spots! The remedy here is to go over the top of your 12″ batts with additional 12″ batts that are perpendicular and cover up the gaps. This will solve the R-value problem and the loss at the trusses causing gaps.

Addressing the 2nd misconception, you will see in the map below, that those living in prairie states like Nebraska have an even greater R-value need than those in cold Minnesota! This is due to the windy conditions. Wind will sap your home faster than cold every time. So if you live in a wide open area where temps get below freezing, you should assume you need R49.

Finally, those living down south still need R49 in their attic! This is due to the AC costs in the summer. With little or no insulation in the attic, the heat from outside will cause your AC to work non-stop. After all, your ceiling consists of as much surface area as your floor. Heat will naturally flow from hot to cold.

For more information on this topic, see my articles at


R-Value Chart
Map and Chart Used With Permission From US Department of Energy

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