How Much Insulation Do I Need in my Attic?

All too often, air is exiting our attics without us even knowing. And as a result, money is rapidly exiting our bank accounts. When money goes to die on wasted energy, public enemy number one is usually not having the proper amount of insulation installed in the attic. Like many Americans, perhaps you’re asking yourself “how much insulation do I need in my attic?” 

Read on to find out.

The Telltale Signs That Your Insulation Needs Attention

A massive spike in your energy bill is typically a dead giveaway that your attic insulation requires immediate attention. But there are visual cues that can tip you off as well.

Take a look around your crawl space and see if you identify these telltale signs:

  • Dark Spots – When dark spots are splattered throughout your insulation material, that indicates one of two things, and neither is good news. Either your insulation has developed mold, or the spots are being created by consistent air leakage.
  • Shifting Cellulose – One of the flaws with loose-fill cellulose insulation is that it settles over time and, as a result, tends to shift toward the middle. If you notice that your cellulose has bunched up in the middle of a joist and left the outsides barren, redistribute the cellulose so that it’s evenly spread out.
  • Settling Fiberglass – Like cellulose, older fiberglass insulation manufactured in the past tends to settle as well. But when it does, instead of shifting, the dark pink “cotton candy look” it had when you first purchased it becomes a distant memory and fades into a shade of pink so dull it’s almost white.
  • Wetness – As soon as insulation gets wet, it’s useless. And that’s not the only problem: it’s also potentially hazardous, as wet insulation can trigger the release of harmful toxins (in the air). Replace wet or even damp insulation immediately and see if you can identify what caused it. Aside from the obvious of a recent flood, the moisture may have been caused by a blocked vent, leaky roof, or the absence of an effective vapor barrier.
  • Rodent Infestation – The most glaringly obvious sign that your insulation needs immediate replacement is when your batts are joined by bats or local rodents and critters have made your joists their local haunt. If this is the case, give the joists a thorough examination to ensure your uninvited “guests” didn’t leave behind any of their children or feces, and then pitch it ASAP.
  • Fluctuations in Your Home’s Temperature – Some signs won’t be visual ones, but rather you’ll be able to sense them. If you feel indoor drafts or drastic fluctuations in temperature, that’s usually a cry for help from your insulation. This can be a clear indication that your insulation needs to be checked for issues.

OK, Looks Like I Need New Insulation. How Do I Figure Out How Much I Need?

If you’ve encountered one or more of the above warning signs in your home, you can go in one of two directions:

  • In less severe cases, you can simply add to the insulation you already have in place
  • In dire cases, you can rip out the prior insulation and start from scratch with brand new insulation, fiberglass insulation

In either case, your next step will be to calculate your attic’s R-Value.

What on Earth is R-Value of Insulation?

Attic insulation R-Value is basically the effectiveness with which an insulator traps heat and keeps it in the room. The higher the R-value, the higher the effectiveness of the insulation. R-value is depending on a few things such as material, thickness, and density. 

How do I Know What R-Value my Attic Needs?

The Us Department of Energy has created this useful chart to help American homeowners decipher the R-Value they need to maintain in their attic. In general, the colder the climate where the house is located, the higher the R-Value in the attic needs to be.

Thus, most US states abide by the following R-Value recommendations:

  • Between R49 and R60 for cold climates, depending on the severity of the winter
  • About R38 for moderate climates
  • As low as R30 for hot climates

Deciding how much insulation your attic needs is a matter of knowing the R-Value of your insulation material and the total R-Value you need your attic to meet, then purchasing enough material to make the equation work. Keep in mind, if you’re adding to previously installed insulation, you’ll need to factor the R-Value of the old insulation materials into the equation as well.


Perhaps now you’re saying to yourself “this whole R-Value stuff is a bit more than I want to deal with.” Thankfully, at Attic Construction, we specialize in guiding you through every step of the installation or removal process for attic insulation.

Contact us today for help determining the R-Value you need to maintain in your home, and learn how we can help you get there!


1) “Batts, Blown or Sprayed? What’s the Best Attic Insulation?” by Allison Bailes

2) “Attic Insulation Types” by Rueben Saltzman

3) “Read This Before You Insulate Your Attic” by Mickey Goodman

4) “Insulation” by the US Department of Energy

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