Serving Nationwide, all 50 statesAttic Insulation Help connects you with licensed local companies. We are not a contractor and do not perform the work ourselves.
info@atticinsulationhelp.com
Attic Insulation Help
Email Us
United States

How much attic insulation do I actually need?

ENERGY STAR recommends R-30 to R-60 for attics depending on climate zone. See the target for your zone and how many bags of blown-in that takes.

Request a Quote
How much attic insulation do I actually need?
How much attic insulation do I need?

It depends on your climate zone. For an uninsulated attic, ENERGY STAR recommends R30 in the warmest US zone up to R60 in the coldest, based on the 2021 International Energy Conservation Code. If you already have three to four inches up there, the topping-up target drops to roughly R25 to R49 depending on zone.

Figures as cited in Sources below
Climate zoneUninsulated atticAttic with existing 3-4 inches
Zone 1 (warmest)R30R25
Zone 2-3R49R38
Zone 4 (A and B)R60R49
Zones 4C-8 (coldest)R60R49

How many bags of blown-in insulation is that?

Most U.S. attics target about R-38, roughly 10 to 14 inches of blown-in material. Bag coverage depends on the target R-value and material: a bag of blown fiberglass covers about 31 to 77 square feet, and cellulose covers about 13 to 23 square feet (HVAC.com, 2026). Divide your attic's square footage by the bag's coverage rate at your target R-value to get a bag count - the coverage chart printed on the bag is the source to use, since it varies by brand and density.

Sources

2 cited
  1. R-value targets by climate zone: ENERGY STAR, Recommended Home Insulation R-Values, based on 2021 IECC Table R402.1.3 (checked 2026-08-19).
  2. Bag coverage rates for fiberglass and cellulose: HVAC.com, How Much Does Blown-In Insulation Cost?, 2026 (checked 2026-08-19).
How it works

How blown-in insulation is actually installed

Four steps, done in order. The Department of Energy is explicit that skipping the air-sealing step is the most common way a new insulation job still leaves an attic underperforming.

Request a Quote
  1. 1

    Air seal first

    The EPA recommends sealing attic-floor penetrations before insulating, because loose-fill does not stop air moving through gaps around wiring, pipes and fixtures.

  2. 2

    Add baffles and depth markers

    Rafter baffles keep blown material off the eaves where it could get wet, and depth rulers mark the target R-value before the blower starts.

  3. 3

    Blow to depth

    A pneumatic machine feeds loose fiberglass or cellulose over the attic floor, covering the tops of the joists so heat cannot bypass the insulation.

  4. 4

    Verify and clean up

    The settled depth gets checked against the target R-value for your climate zone, then tools and debris are cleared.

How we work

What this site will and will not do

We explain the R-value target and the real cost drivers first, and we do not sell you the installation - which is why we can say plainly when topping up beats a full replacement.

01

R-value before a quote

ENERGY STAR recommends R-30 to R-60 depending on your climate zone. Knowing your target before you call means you can hold every bid to the same number.

02

Air sealing first, always

The Department of Energy is explicit that insulation slows heat flow but does not stop air leaks - sealing gaps first is what makes the insulation you pay for actually perform.

03

We are not the installer

We do not install anything ourselves, so we have nothing to gain from steering you toward the bigger job. Licensed local companies do the work and quote it themselves.

04

Nothing we cannot source

Every figure on this site traces to a named, dated source - HomeAdvisor, the DOE, ENERGY STAR, the EPA or the FTC. Where we have not sourced a number, we say so instead of guessing.

Questions

Frequently asked

The questions people actually type before calling a company.

Request a Quote
What R-value should attic insulation be?

ENERGY STAR recommends R30 in the warmest US climate zone up to R60 in the coldest, based on the 2021 IECC. Check the table above for your zone.

How many bags of insulation do I need for my attic?

Depends on material and target R-value: a bag of blown fiberglass covers about 31-77 sq ft, and cellulose covers about 13-23 sq ft (HVAC.com, 2026). Use the coverage chart printed on the specific bag you're buying.

Get matched with a licensed local insulation company

Request a QuoteEmail Us
Request a QuoteEmail Us