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.
In temperate coastal areas such as Zone 3, attic insulation of at least R30 up to a maximum of R60 is recommended. For loose-fill cellulose, this translates to a total depth ranging from 8 inches up to 16 inches.
Cost: Blown-in insulation is perfect for the weekend warrior looking to get the job done cheaply. There is little learning curve involved with the application, and a DIY job will cost you about $500. Calling in the pros, on the other hand, will run you about $1,500 to $2,000 for an average 1500 square foot home.
Blown in Fiberglass Attic Insulation
| R-Value | Minimum Thickness | Minimum Weight/ Sq ft |
|---|
| R49 | 19.1” | 0.774 |
| R44 | 17.4” | 0.686 |
| R38 | 15.3” | 0.583 |
| R30 | 12.4” | 0.450 |
10 bags/pallet is equal to 110-pieces/1065.60 sq. ft. The right insulation can save on energy and heating and cooling bills.
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.
If you've ever touched fiberglass insulation with your bare hands, you're probably well aware of its effect on the skin. In most situations, touching the material without proper protection will result in a sharp stinging, burning and itching sensation.
Blown-In Insulation Cost
| National Average Cost | $1,665 |
|---|
| Minimum Cost | $646 |
| Maximum Cost | $2,681 |
| Average Range | $874 to $2,156 |
R-19 Kraft Faced Fiberglass Insulation Roll 23 in. x 39.2 ft.
From a performance standpoint, the best type of insulation is spray foam. There are two types; closed-cell and open-cell, aka 2-pound and ½-pound, respectively. They have insulation values of approximately R-6.5 and R-3.6 per inch, respectively.
R-38 is the industry standard, and the minimum thickness for R-38 is 12 inches. If your current insulation is only five inches deep, you will need to add seven inches of insulation to achieve the 12-inch R-38 rating. Measure the area needing insulation. Measure the length and width of the area you need to insulate.
According to ENERGY STAR®, you can put new insulation over old insulation, “unless it is wet. “Faced” insulation should not be placed on top of existing insulation in the attic. Any new batt or roll insulation installed over existing insulation in the attic needs to be without a vapor retarder (face).
One of the places in your home where a little bit of attention can make a big difference in your comfort — and heating bill — is the attic. According to the Department of Energy, properly insulating the attic can save 10 to 50 percent on a typical heating bill.
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).
In such situations, blown-in insulation is much more effective since it allows you to easily insulate those hard to reach areas. Another thing to keep in mind is that blown-in insulation can be more cost-effective depending on the attic situation.
Cellulose Chart
| R-Value | Min Thickness | Bags / 1000 Sq Ft |
|---|
| R49 | 15” | 75.2 |
| R44 | 13.4” | 66.2 |
| R38 | 11.6” | 55.5 |
| R30 | 9.3” | 42.7 |
| R-value of Materials and Depths |
|---|
| Material | R-value/in | 10" |
|---|
| Mineral Wool blown (wall) | 3.1 - 4.0 | 31.0 - 40.0 |
| Cellulose blown (attic) | 3.2 - 3.7 | 32.0 - 37.0 |
| Cellulose blown (wall) | 3.8 - 3.9 | 38.0 - 39.0 |
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. This means you could use R38 insulation, and then add another layer of R13, for a total of R51….
For loose-fill cellulose, this translates to a total depth ranging from 8 inches up to 16 inches. Fortunately, attic insulation can be upgraded simply by adding more to achieve the recommended total depth in inches, without removing existing insulation.
Fiberglass batts for standard 2×4 walls are now available in low, medium, and high density products that range from R-11 to R-15. Sprayed foam insulation in the same wall cavity can range from an R-14 to an R-28 depending on the product that is used.
For future reference, here is the cavity depth you need for some common insulation r-values: 3.5 inches --- R13. 6 inches --- R19. 9 inches --- R30.
To find the
R-
value of the existing
insulation in your attic, multiply the number of inches of
insulation by the
R-
value for your particular type.
Cold Climates (R-49 to R-60):
- Fiberglass (blown): 19” – 25”
- Fiberglass (batts): 14” – 19”
- Cellulose (blown): 14” – 18”
- Rock Wool (loose): 17” – 25”
- Foam (sprayed): 7” – 15”
Vacuum insulated panels have the highest R-value, approximately R-45 (in U.S. units) per inch; aerogel has the next highest R-value (about R-10 to R-30 per inch), followed by polyurethane (PUR) and phenolic foam insulations with R-7 per inch.
