In general, either batt or rolled insulation or blown
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.
Is it possible to add new insulation overtop existing insulation rather than replacing it entirely? Yes, it is possible and often recommended to retrofit insulation in your attic or other parts of your home rather than completely replace the insulation.
Insulation needs to have room to expand to its full size to be effective, so the old definitely needs to be removed. Not to mention the old stuff is full of dust, probably some rodent excrement, and who knows what else that has accumulated in your attic over the years, so that's another reason to get rid of it.
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.
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.
An over-insulated house is susceptible to mold since it is so tightly sealed that it prevents moisture from escaping. It also prevents air from entering, circulating, and exiting, which can significantly reduce indoor air quality.
Enhanced R-Value and Energy Efficiency: Blown-in insulation significantly improves your home's R-value, which is a measure of heat resistance. This means your home will stay warmer in the winter and cooler in the summer, helping you save up to 30% on heating and cooling costs.
Blown-In Insulation (Fiberglass And Cellulose)
Because it is both efficient and economical, blown-in or loose-fill fiberglass is an insulation material that sees widespread use. In most homes, loose-fill insulation can survive anywhere from 80 to 100 years before needing replacement, provided that it is not damaged.
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.
If your insulation is just level with or below your floor joists (i.e., you can easily see your joists), you should add more. If you cannot see any of the floor joists because the insulation is well above them, you probably have enough and adding more may not be cost-effective.
Yes, too much loft insulation can cause dampness in some situations. Loft insulation works by trapping warm air inside a building, preventing it from escaping through the roof. This helps to keep the interior of the building warmer in cold weather, reducing the need for heating and saving energy.
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.
Unless your home was specially constructed for energy efficiency, you can probably reduce your energy bills by adding more insulation. Many older homes have less insulation than homes built today, but even adding insulation to a newer home can pay for itself within a few years.
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.
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.
Removing old insulation is generally recommended if it's damaged, contaminated with mold, or infested with pests. However, if the insulation is in decent shape and just needs a boost, adding a new layer on top can be a cost-effective option.
On average, the cost of blown-in insulation ranges from $1.50 to $2.80 per square foot, leading to an average cost of blown-in insulation between $1,500 and $2,800 for a 1,000-square-foot area.
Both cellulose and fiberglass are energy-efficient insulation materials, but cellulose has a slight edge due to its higher R-value. The R-value for cellulose insulation is approximately 3.2 to 3.8 per inch, while fiberglass insulation typically has an R-value of 2.2 to 2.7 per inch.
Provided the existing rolls are in good shape, you can absolutely retrofit batt insulation with blown-in insulation! Materials can even be mixed, such as blowing in cellulose insulation on top of fiberglass batts (or vice-versa).
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.
Adding two R-13, 3.5” batts to a 2”x6” (5.5”) wood stud cavity will not provide an R-26. The total of 7” of insulation is reduced in thickness to 5.5” thereby losing the R-value associated with its full thickness.
The optimal R-value for most homes is 30, but you can go as high as 38 if you live in a tropical climate. Anything higher than 38 indicates an over-insulated space. While you might think that too much insulation can't be bad, there are some significant consequences to consider.
Walls, floors and ceilings should feel warm and dry to the touch in your home. An indication that there is not enough insulation can be drywall or paneling feeling damp or cold. Conversely, the walls outside of your home should feel cold because insulation stops the heat from escaping.