Too much insulation will leave humidity and moisture to accumulate in your attic space. This can lead to mold growth on your walls and insulation. There might also be water damage to the support beams in your home's roof.
Mold in the Middle
It is possible to over-insulate your house so much that it can't breathe. The whole point of home insulation is to tightly seal your home's interior. But if it becomes too tightly sealed with too many layers of insulation, moisture can get trapped inside those layers. That's when mold starts to grow.
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.
As a general guideline, it's advisable to install double layers of thermal insulation throughout your house. Nevertheless, this may not be feasible in all areas due to space limitations. Typically, it's not practical to add two layers of insulation within the walls of your home.
Over-insulating a house has no negative impact on energy usage, comfort, or air quality. We don't recommend over-insulating a home because it is not a wise financial decision. However, we will always recommend the right amount of insulation that delivers a dramatic ROI, a more comfortable home, and better air quality.
Can Insulation Be Packed Too Tightly? Yes, it can. It all comes down to the R-value, or the insulation's resistance to heat.
If installed properly, Greenfiber ensures the product will be free from defects and will not deteriorate under normal and proper use for the lifetime of the structure. You can blow cellulose insulation on top of fiberglass to bring a home's energy efficiency to an optimal level.
It's a reasonable question—after all, if one layer of insulation is good, wouldn't two be better? Unfortunately, the answer is no. Stacking insulation doesn't improve R-value in the way you might think, and it can actually create more problems than it solves.
R19 Insulation offers superior thermal insulation compared to R13. With a typical thickness of 6.25 inches, R19 fiberglass is designed for use in 2x6 wall cavities, making them suitable for colder climates where higher thermal resistance is necessary.
You should install two layers of insulation in your attic; wood joists must be covered to allow the air to move. The first layer will sit between the joists, and the second layer will run perpendicular over the joists. The first layer should have the facing against the drywall to act as a vapor barrier.
Insulation depth
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. For an accurate depth for a given type of insulation there is a chart on the insulation bag noting the required depths for various R-values.
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).
Safety concerns: Attics may not be designed to support heavy loads, raising safety concerns about overloading the attic with too many or too heavy items, potentially compromising the home's structural integrity.
Too much insulation will leave humidity and moisture to accumulate in your attic space. This can lead to mold growth on your walls and insulation. There might also be water damage to the support beams in your home's roof.
Looking across your attic, if the insulation is level with or below the attic floor joists, you probably need to add more insulation. If you cannot see any of the floor joists because the insulation is well above them, you probably have enough, and adding more insulation may not be cost-effective.
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.
You will want to bring up your attic up to R-38:
If your attic has 5-6″ of existing insulation, you'll want to install an R-19 to achieve a total of R-38.
R15 insulation offers slightly better thermal insulative properties than R13. Some of its formats are a fraction of an inch thicker than R13, making it more effective at helping with energy efficiency. However, the difference is minimal. R15 is slightly thicker than R13 for spray foam and blown-in cellulose.
The recommended R-value for attic insulation can vary depending on the climate zone in which you live. 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.
ABOUT INSULATION
The thermal barrier of a home should consist of a continuous layer of insulation on all sides—including the lowest floor, the exterior walls, and the ceiling or roof. Doubling the thickness of insulation will double the insulation's R-value, cutting heat loss in half.
For example, if the square footage of the room you're planning on insulating is 1,000 square feet and you want to achieve an R-value of 60, you will need approximately 17 bags to fully insulate your room. If you are using loose fill insulation, the coverage varies based on the R value that is needed.
In general, either batt or rolled insulation or blown loose-fill insulation (fiberglass or cellulose) can be installed on top of old insulation. If you need to add new insulation on top of old insulation please note the following: Draftproofing should be completed prior to the addition of more insulation.
While cellulose insulation offers many benefits, its susceptibility to moisture damage is a notable drawback. If exposed to moisture, the paper fibers can absorb water, leading to mold growth, reduced insulation effectiveness, and potential structural damage to the building.
It's also fire-resistant. Rodents generally are not drawn to cellulose insulation, either.
Spray foam: Open-cell or closed-cell spray foam can provide excellent insulation and air sealing in one application. Combination approach: Use spray foam to seal air leaks and fill odd-shaped cavities, then supplement with batt insulation for cost-effectiveness.