What is the best type of insulation for attics

Many people consider fiberglass batt to be the best attic insulation. It consists of plastic reinforced by small glass fibers. The batt version comes in blanket form — i.e., small, pre-cut sections that you can lay down wherever you need to.

What is the most effective attic insulation?

Blown-in Insulation Fiberglass, cotton, and mineral wool can all work as loose-fill material, but the far and away top choice for blown-in insulation is fiberglass. Contrary to batts insulation, blown-in fiberglass insulation is perfect for filling in tight voids around wiring, pipes, or any area with awkward framing.

Which is better for attic insulation cellulose or fiberglass?

At 3.5 per inch of material, the R-value of blown-in cellulose is 23% better per inch than fiberglass batts! According to research done at the Oak Ridge National Lab, fiberglass loses up to 50% of its R-value in very cold conditions; making cellulose a better choice for homes in northern climates.

What is the most common attic insulation?

By far, the most frequently purchased type of attic insulation material is fiberglass, extremely delicate glass fibers that are comprised of recycled material and sand and look uncannily like cotton candy.

What R-value should I have in my attic?

R-Value is a measure of insulation’s ability to resist heat flow. 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.

How much does it cost to insulate a 1500 sq ft attic?

How much does it cost to insulate a 1,500 sq ft attic? With average costs ranging from around $1 per sq ft to $5 per sq ft (excluding structural insulation panels as these are best for new installations) expect to pay from $1,500 to $7,500 to insulate a 1,500 sq ft attic.

Is R30 insulation good for attic?

R30 insulation is the minimum insulation recommended for an Attic from climate zone 1 to 3, while it can be used in cathedral ceilings in all climate zones across the USA. It can be used as maximum insulation in climate zones 4 – 8 of the USA for floors.

Does fiberglass insulation break down?

Unless damaged, it can last 80 to 100 years in most houses before it needs to be replaced. However, insulation can start falling from fiberglass batts after 15 to 20 years, so if your insulation was installed in batts well over a decade ago, it might be time for an inspection or a home energy audit.

Is rolled insulation better than blown?

Rolled fiberglass insulation scores an R-value of 3.7. So overall, rolled fiberglass insulation is slightly more effective at blocking in and out heat than its blown counterpart.

Does cellulose insulation lose R-value?

As a loose-fill insulation, cellulose provides high insulating values, represented by its higher R-value, and it creates a good barrier against air leaks and infiltration. However, like other loose fill insulation, it also has a tendency to settle over time, reducing its R-value and its ability to prevent air movement.

Article first time published on

Is R 19 insulation Good for attic?

Most homes only have R19 in attics. To give you an idea that’s only 5 1/2 inches of insulation. … So by adding another R19 “5 1/2 inches will give you an R38 value. And that’s a good number to live with.

What is better R13 or R15?

Is R15 Better than R13? Answer: There isn’t much difference between R13 and R15. However, higher R values offer higher performance. Therefore, in the case of efficiency, R15 is better than R13.

Can you put new insulation over old?

According to ENERGY STAR®, you can put new insulation over old insulation, “unless it is wet. … The vapor retarder on top of or between layers of insulation can trap moisture. Any existing batt or roll insulation in the attic should have the facing against the attic drywall floor or no facing at all.

What is the difference between R13 and R19?

There is a direct relationship between the amount of insulation and the amount of heat transfer. The bigger the R value, the better the insulation is at slowing down the heat transfer. So R19 is better insulation than R13, and R30 is better than R19. The larger the R value, the better the insulation value.

What is R 11 insulation used for?

The Johns Manville R-11 Kraft-Faced Fiberglass Insulation Batt is a revolutionary insulating material that is ideal for controlling moisture of exterior walls. It is available in pre-cut sizes that make them suitable to fit in different types of standard wall cavities.

What is the difference between R19 and r21 insulation?

R-21 insulation has a higher density than R-19, although it is designed to fit into the same space. It tends to be slightly thinner than R-19 because of its density. … R-21 insulation is more efficient at preventing the transfer of heat, but it costs more per square foot.

Will insulating my attic make my house cooler?

The first way insulating material cools a home is by not letting it get too hot in the first place. … However, insulating the attic also prevents cool air from escaping because it reduces the movement of air, also called convection. Overall, the average home can save 10 percent on cooling by insulating the attic.

Can you have too much insulation in an attic?

It’s possible to over-insulate an attic as too much will cause moisture buildup and eventually result in mold. Eventually, adding more insulation leads to diminishing returns in trapping heat as well.

How thick should blown-in attic insulation be?

When blown into attics and wall spaces, loose-fill fiberglass offers an average R-2.5 thermal value per inch (the higher the number, the greater the insulating effect). You’d need a thickness of about 7.5 inches of insulation to match the insulating value of a batt of R-19 insulation (R-19 is a common batt value).

How do you tell if your attic is properly insulated?

While you’re at it, feel the ceiling and see if it seems strangely hot or cold in any area. If any rooms have odd temperature changes, there’s a good chance that the insulation in that area is poor and will need to be replaced. Note that ceilings aren’t the only areas where insulation can be poor.

How long does insulation in attic last?

The typical lifespan of attic insulation according to the International Association of Certified Home Inspectors says that spray foam insulation, house wrap insulation, and wrap tape can last up to 80 years or longer. Cellulose, foamboard, loose-fill, and rock wool insulation can last 100 years.

Does fiberglass insulation lose R-value over time?

Here’s what they found: The fiberglass batts and loose-fill cellulose performed as expected at the whole range of temperature differences. The loose-fill fiberglass showed a significant reduction in R-value as the attic got colder and the temperature difference got larger.

Does cellulose insulation deter mice?

Cellulose insulation is a deterrent for mice and other types of pests. Pests prefer solid materials where they can burrow and nest. The dry composition of the insulation makes it difficult for most pests and mice to survive.

What happens if cellulose insulation gets wet?

How Water Inundation Impacts Cellulose Insulation. Cellulose is a loose-fill product. The material is designed to fill space with the “fluff” of the fibers to prevent voids and air pockets. When the fibers become wet to an excessive level, their weight increases, and the material will slowly compress and settle.

Is it OK to put cellulose insulation over fiberglass?

No. Even if you have moisture in your attic, once all bypasses are sealed (and/or your roof repaired by a qualified contractor, if necessary) cellulose is blown directly over the existing insulation. … Adding new cellulose insulation on top of existing fiberglass insulation is called “capping”.

What is the code for insulation in an attic?

ZoneAdd Insulation to AtticUninsulated AtticExisting 3–4 Inches of Insulation1R30 to R49R25 to R302R30 to R60R25 to R383R30 to R60R25 to R38

How much does it cost to insulate a 1000 sq ft attic?

Square FeetPrice1,000$1,000 – $7,0001,500$1,500 – $10,500

Is R-13 insulation Good for attics?

Depending on where you live and the part of your home you’re insulating (walls, crawlspace, attic, etc.), you’ll need a different R-Value. Typical recommendations for exterior walls are R-13 to R-23, while R-30, R-38 and R-49 are common for ceilings and attic spaces.

Can you put R15 in 2x4 wall?

Insulation for 2×4 Walls In most wall applications, you will use R-13 or R-15 kraft-faced fiberglass insulation rolls for these two-by-four stud walls. While rated differently, these two types of insulation are close enough in thickness that they can both fit into modern two-by-four wall systems.

What's the difference between r11 and R15 insulation?

R-value refers to resistance of heat transfer. The greater the limitation, the greater the R value, so R-11 has lower insulative properties than R-15. …

How much does it cost to get insulation blown into attic?

Blown-In Attic Insulation Costs The cost to insulate an attic with blown-in insulation runs from $600 to $1,200, assuming it is 1,000 square feet in size. If you choose to hire a professional, expect to pay from $40 to $70 an hour for labor in addition to the cost of materials.