Can Your House Have Too Much Insulation?

When you think of home efficiency, the first thing you probably think about is your home’s heating and cooling system and whether it operates at its potential. However, properly insulating your attic spaces and walls can significantly improve the efficiency of your home, keep it more comfortable and even save you money on your energy bill.

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Over-insulating can also lead to a multitude of problems, including moisture retention and diminishing returns on your investment. This article explains some of these issues and helps you determine how much insulation is too much and whether you can have an R-value that’s too high.

Is It Possible to Have Too Much Insulation in Your Home?

Home insulation comes in a variety of materials, such as fiberglass, rock and slag, spray foam, rigid foam and cellulose insulation, with fiberglass being the most common. Additional insulation installed in your home limits heat conduction and creates an airtight seal. As a result, insulating your home makes it more energy efficient and helps you maintain a consistent temperature year-round. When installing insulation, the goal is to determine the proper depth and R-value your home requires to be cost-effective. Anything more is a waste of money.

One of the issues with installing too much insulation is moisture retention. When you pack insulation too tightly, moisture can trap inside your walls and in the attic to limit airflow, which leads to mold and mildew growth.

How Much Insulation Is Too Much?

The amount of insulation needed for home comfort depends on several factors, including where you live, what your home is made of and the type of insulation you plan to use. For example, if you live in the southern United States, the recommended level of insulation is R-38, or approximately 13 to 14 inches of insulation. For colder northern states, you’ll need more insulation to achieve the same level of efficiency. Different areas of your home also require different levels of insulation.

• Attic. Your attic insulation should have R-values between R-30 and R-60. These higher levels are recommended because heat rises, which can result in significant heat loss for other floors in the home.

• Walls. Install between R-13 and R-23 for exterior and interior walls.

• Floors. For floors, use between R-13 and R-25. The specific value depends on where you live. Use lower levels in warmer climates and higher levels in colder climates.

How Do You Know How Much Insulation You Have?

You can check the amount of insulation you have in your home by using a tape measure to determine the depth. Each R-value is equal to a depth of 3 to 3.5 inches. Multiply the depth of your insulation by 3 to get the current R-value amount of insulation if it's fiberglass. For other types of insulation, consult the vendor or go online to determine how to calculate the R-value.

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Can Your Insulation Have an R-Value That is Too High?

Home insulation is measured by its R-value. The higher the rating, the greater the insulating power. The R in R-value stands for resistance to heat flow. When shopping for insulation, you’ll see the R-value printed on the packaging or directly on the insulation. While higher R-values mean greater efficiency, at some point, installing a higher number leads to only marginal improvements. For example, if the recommended insulation value for walls is between R-13 and R-23, increasing in number only provides marginal heat loss benefits. At some point, the cost of the insulation will be more than the energy savings it provides.

The type of insulation also determines how effective high R-values are. Common insulation types include:

• Spray foam. Spray foam can cover a greater area and fill in the smallest cracks. However, over-applying it can limit airflow and increase moisture.

• Fiberglass batting. Fiberglass insulation comes in rolls and is one of the easiest to install. Gaps in the insulation can cause heat loss, making it one of the least efficient.

• Cellulose. Cellulose insulation is made from recycled materials. Too much cellulose insulation can lead to compacting, which lessens the efficiency.