How thick should blown attic insulation be?

Asked By: Najih Fontan | Last Updated: 23rd January, 2020
Category: home and garden indoor environmental quality
4.4/5 (30 Views . 33 Votes)
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.

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Keeping this in consideration, can you put too much insulation in your attic?

But there may be a theoretical point of “too much.” If a home is over-insulated and is too tightly sealed, moisture can get trapped inside. Without proper ventilation, a home can build up too much moisture, especially in the attic (warm air rises), which can cause mold problems and, overall, lower indoor air quality.

One may also ask, how much insulation do I need in the attic? According to the U.S. Department of Energy, it's recommended that attics have an R-38 to R-49, or about 12” to 15” of fiberglass or cellulose insulation. Use unfaced insulation when adding more insulation to an attic that already has some insulation, laying the rolls or batts at right angles to the floor joists.

Hereof, which blown in insulation is best for attics?

The best insulation options for an attic are open cell spray foam, fiberglass, and cellulose.

  • Cellulose is the oldest insulation material used for not only the attic, but other areas of the home as well.
  • Fiberglass is another traditional insulation material that consists of extremely fine glass fibers.

How thick is r48 insulation?

Compare all Specifications

Insulation Location Attic Insulation Location Ceiling
Roll or Batt Batt Roll or Batt Batt
Product Length (ft.) 4 ft Product Length (ft.) 4 ft
Faced or Unfaced Faced Faced or Unfaced Faced
Product Thickness (in.) 14 in Product Thickness (in.) 8.25 in

39 Related Question Answers Found

Can you lay insulation over electrical wires in attic?

If there is not anyinsulation in your attic, fit the insulation between the joists. Don't compress the insulation to fit behind pipes or wires. Instead cut to the middle of the batt's thickness so you have a flap under the wire and one over the wire.

Is it OK to put flooring over blown in insulation?

If blown-in insulation is used, control the height or thickness of the layers so boards can by laid over top without having to compact the filler.

Is rolled insulation better than blown?

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.

Should I remove old attic insulation before adding new?

Do I Need to Remove Old Insulation Before Adding New Attic Insulation? Your current attic insulation will form the basis of the additional attic insulation that you are planning to install. Therefore, unless it is damaged or your roof is damaged, you should not have to remove the original insulation.

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.

How much does it cost to have 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.

Is air sealing the attic worth it?

Air sealing your attic is essential to an energy efficient home. Air sealing your attic and having it appropriately insulated helps minimize the stack effect. This will make your home's temperature more comfortable and easy to regulate, while protecting you against high energy costs year-round.

How do you seal an attic?

Plug the big holes first.
  1. Create stuffed bags.
  2. Plug open stud cavities.
  3. Cover dropped soffits.
  4. Seal behind kneewalls.
  5. Cut aluminum flashing.
  6. Seal with silicone caulk.
  7. Form an insulation dam.
  8. Find attic bypasses.

What is cheaper blown in insulation or fiberglass?

Fiberglass batts, however, are less expensive, costing on average $0.30 to $0.40 a square foot for 6 inches of insulation. Installation costs for blown-in insulation costs around $2 a square foot, where installation costs for batts is around $1 a square foot.

Is blown in insulation cheaper than batts?

Blow-in insulation is quite comparable in cost and R-value when compared to fiberglass batts or blankets. DIY-friendly. Blow-in insulation is difficult for DIYers, especially for wall cavities. Attic insulation can be a DIY project with a rented or borrowed blower but is still a challenge.

How often should attic insulation be replaced?

Insulation should also be replaced, in some cases sooner than 15 years, if it is no longer doing its job properly. You'll know it needs to be replaced if there are insulation leaks or if it is peeling from the walls.

How much money can you save by insulating your attic?

Add attic insulation to lower heating and cooling costs by as much as $600 per year. Save about $600/year by boosting the amount of attic insulation from R-11 to R-49.

Does blown in insulation help with soundproofing?

Two of the best soundproofing insulation materials are loose-fill cellulose and fiberglass. Blown-in insulation provides a twofold benefit, both adding insulation and soundproofing to your home. This is a perfect twofer, since if you're trying to reduce noise, you might as well reduce your utility bills!

Should I remove old blown in insulation?


Remove Old Insulation
Once there is no asbestos, mold, or rodents, it is generally safe to proceed with attic insulation removal yourself. Luckily homeowners are more likely to find the easier kind which is blown-in fiberglass or cellulose insulation. Removing rolls or batting is a bit harder, but can be done.

How much does it cost to insulate a 1200 sq ft attic?

On average, most homeowners spend between $813 and $1492 or $1.50 to $3.00 per square foot to install attic insulation. Pricing depends on the size of your attic, the type of insulation material used, and labor rates. For example, blown-in insulation for an attic in a 1,200 square foot home costs about $1,850.

How do I know if my attic needs insulation?

A quick way to see if you need more insulation is to look across your attic floor. If your insulation level is at or below the top of the floor joists, you probably need to add more insulation (but remember to seal the air leaks before you insulate).