How much insulation do I need in my attic?

Author: Dr. Gregg Ernser II  |  Last update: Monday, May 12, 2025

The higher the R-Value, the better the thermal performance of the insulation. The recommended level for most attics is to insulate to R-38 or about 10 to 14 inches, depending on insulation type.

Can you put too much insulation in attic?

While loft insulation is an effective way to improve energy efficiency and reduce heating costs, over-insulating can lead to several potential issues. Firstly, over-insulation can lead to poor ventilation in the attic, which can cause moisture buildup and increase the risk of mould growth.

How many inches of insulation should you put in your attic?

If you live in the Southern part of the U.S., the recommended insulation level is a minimum of R-38 or about 13-14 inches of insulation. If you live in the Northern part of the U.S., the recommended insulation level is a minimum of R-49 or about 16-18 inches of insulation.

What is the best R-value for attic insulation?

The U.S. Department of Energy recommends attic insulation levels of R-49 to R-60 for most homes in colder climates, and R-30 to R-49 for homes in warmer climates.

Should I remove old attic insulation before adding new?

Do I Have To Remove Old Insulation? Unless your insulation is wet, moldy or infested with pests, you don't need to remove it before adding insulation on top of it. ENERGY STAR® recommends that you inspect your insulation for signs of mold, mildew, moisture and pest infiltration before making this determination.

Things To Know Before Insulating Your Attic | Improve Comfort

Which is better, attic insulation blown or rolled?

Blown fiberglass insulation scores an R-value of 3.2 to 3.8, making it slightly less likely than rolled fiberglass to prevent the flow of heat into and out of your house. That being said, though, blown fiberglass insulation isn't meant to cover huge areas like rolled fiberglass insulation.

How do I know if my attic is insulated enough?

If your home, or upper floor, is too hot in the summer and too cold in the winter it is likely that you have insufficient attic insulation. If a visual inspection of your attic identifies that the insulation is level with or below the attic joists – you need more insulation.

Is adding insulation to an attic worth it?

Should you insulate your attic roof? Insulation is a wise choice to increase the energy efficiency of your home. Quality insulation will make it more cost-effective to heat and cool your home, The Department of Energy's estimates range from a 10% to 50% savings, depending on several factors.

What is the thinnest insulation with the best R-value?

The thinnest insulation material currently available on the market is the 10mm Aerogel blanket. Its manufacturing technology is highly interesting, and its appearance resembles frozen smoke. For some, aerogel is synonymous with time frozen and suspended in space.

Do you need 2 layers of insulation in attic?

Overall, the second layer of insulation plays a crucial role in improving insulation performance, reducing heat loss, and maintaining a comfortable and energy-efficient living space.

How many years does attic insulation last?

Conclusion. Attic insulation can last 80 to 100 years, though it loses its energy efficiency benefits with time.

How do I calculate insulation for my attic?

To do so, take the square footage of the space and divide it by either the depth or the desired R-value. Our blow-in insulation calculator can help take the guesswork out of scoping and pricing for your next cellulose insulation project.

Where should you not put insulation in the attic?

Also, when laying down additional insulation, work from the perimeter toward the attic opening. Never lay insulation over recessed light fixtures or soffit vents. Keep all insulation at least 3 inches away from recessed "can" lights, unless they are rated IC (Insulated Ceiling).

Is it okay to cover attic insulation with plywood?

Can I put plywood over insulation in the attic? Yes you can install plywood subflooring directly over the floor joists and insulation on your floor. You need to install rigid insulation boards on top of the attic flooring joists and then install plywood over the top.

What is the normal amount of insulation in an attic?

The higher the R-Value, the better the thermal performance of the insulation. The recommended level for most attics is to insulate to R-38 or about 10 to 14 inches, depending on insulation type.

What time of year is insulation cheapest?

Best Time of Year to Buy Insulation

In this case, the spring is the best time, because you will also start to see savings in the summer months. The same is true for warmer climates, just different times of year because you'll want the job finished before the heat sets in.

What is the best insulation for attics?

Fiberglass Batt and Roll Insulation

Fiberglass batt and roll insulation is a common and budget-friendly option. This insulation comes in pre-cut batts or long rolls, making it easy to fit between the framing members, like joists and trusses, in your attic.

Can I walk in insulated attic?

Walking in an Insulated Attic

Walking in an attic with insulation on the floor requires a careful balance between maintaining the insulation's effectiveness and modifying the space for safety and utility.

What happens if there is not enough insulation in the attic?

When a home has inadequate insulation in the attic, a lot of air is lost through the roof. Energy bills skyrocket, and it's impossible to keep the temperature in the house regulated.

Should attic insulation be on roof or floor?

Should You Insulate the Attic Floor or Roof Deck? If you are looking for an insulation upgrade that you can see (on your energy bill) and feel (in a home that is more comfortable), we recommend insulating the attic floor, and using radiant barriers on the roof deck.

How big of a difference does attic insulation make?

SAVINGS AND COMFORT

EPA estimates that homeowners can save an average of 15% on heating and cooling costs (or an average of 11% on total energy costs) by air sealing their homes and adding insulation in attics, floors over crawl spaces and basements.

What is the disadvantage of blown insulation?

Cons of Blown-In Attic Insulation:

Poor installation can lead to uneven coverage, material waste, and even structural issues like sagging ceilings. Hiring a skilled installer is crucial to getting the most out of this insulation type.

What is the R-value of 8 inches of blown insulation?

Blown-in insulation has an R value that ranges from 3.2 to 4 per inch depending on the type of material used and where it's installed in the house. This makes it one of the most efficient types of insulation available on the market today.

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