To achieve R-40, we install 12” of
Using the known R- values per inch of each type of insulation, we know that to install R-38 you need from 10” to 12” of cellulose and 14” to 17” of fiberglass.
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.
Cellulose insulation R value per inch is variable, but most cellulose insulation products offer R3. 5-R3. 7 per inch. So, if you need to reach R30 in your attic, you'll need a significant thickness—anywhere from 8.1 to 8.6 inches of depth.
The R-value for cellulose insulation typically ranges from 3.1 to 3.8 per inch. This indicates its thermal resistance or how well it can prevent heat transfer. Cellulose insulation is a popular choice for both residential and commercial buildings due to its eco-friendly nature and efficiency in reducing energy costs.
Mold and Mildew Growth
Having too much insulation in your attic can allow for the accumulation of moisture. This leads to mold and mildew growth, which can be extremely bad for your health.
To achieve R-40, we install 12” of cellulose insulation. To achieve R-50, we install 15” of cellulose insulation.
R38 insulation provides higher thermal resistance than R30, but the additional energy savings may not always justify the increased cost: R38 offers 26% more thermal resistance than R30. Upgrading from R30 to R38 can result in approximately 25% energy cost savings.
(R303. 1.1. 1) Blown-in or Sprayed Roof and Ceiling Insulation | UpCodes.
Cellulose has a slightly better R value per inch; R38 is 11 inches of cellulose, but 13 inches of fiberglass. Fiberglass is not as dusty as cellulose, although the dust settles out in 3 or 4 days after installation. Rodents LOVE fiberglass, but they don't like cellulose.
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.
Fiberglass is by far one of the most thoroughly tested building materials and can be installed in the form of batt or blown-in insulation. Fiberglass is eco friendly, non-flammable, safe to install and maintains its thermal performance for the life of the building.
6 pieces per bag, totaling 48 sq. ft. Compression packaging from Owens Corning speeds job site handling and installation, with less bags required.
Blown fiberglass installed in an attic has an R-value of 2.2 per inch, so 12 inches of it would give you an R-value of 26.4 in your attic installation project.
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.
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).
How thick should blow-in insulation be in an attic? For attics, you should aim for an R-value between 38 and 49, depending on your specific needs and climate zone. To achieve an R-value of 38 to 49 in your attic, you should aim to install 11 to 14 inches of blow-in cellulose insulation.
Divide the square footage of your ceiling joist cavities by the square footage covered per bag of insulation. Round up to the nearest whole number. The result is the number of bags of insulation you need to buy.
R-60 would indicate your are thinking about an attic. Owens Corning "Pro-Pink” would require 20 inches. Applegate Cellulose indicates a 19.75 inches Installed - with 17.25 settled. Certainteed (Insul-sate) fiberglass would be 21.75 inches.