Can You Put New Attic Insulation Over Old?

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Whether you are looking to keep your home warmer in the winter or cooler in the summer, putting new insulation in your attic can help you accomplish that goal. But should you put new attic insulation over the old? We’ve done the research to bring you the answer.

You can certainly have new attic insulation installed over the old, but there are some things to consider first.  Inspect your old insulation for the following:

  • Moisture
  • Condition
  • Asbestos

The condition of your current insulation will help determine if it is appropriate to install new insulation over the old.

How detailed should the inspection be of old insulation? Does adding new insulation really make a difference? How often should attic insulation be replaced? To find the answers to all these questions and more, just keep reading.

A man rolling mineral rockwool insulation on the attic, Can You Put New Attic Insulation Over Old?

Best Practices For Installing New Attic Insulation Over Old

An up close photo of mineral rockwool insulation placed on the attic of a house

Let’s take a closer look at the three things for which you should inspect your old insulation as well as some other considerations to be had.

1. Moisture

Is the old insulation wet or does it show signs of wetness (such as staining)? Do not install new insulation over old if it contains any moisture or shows any sign of previous wetness, as this could potentially create a mold and/or mildew problem.

2. Condition Of Old Insulation

Is the old insulation crumbling apart or showing signs of infestation from rodents or insects? Can you see areas where the old insulation has worn thin? If so, you should not install over the old insulation.

3. Asbestos

An old attic of a residential house

If your home was built before 1950 and your old insulation looks like pebbles, you may have vermiculite insulation that could contain asbestos. These ‘pebbles’ could be either brown, gray, or silver in color. You should not make any attempt to remove this yourself and should contact a certified professional for testing and proper removal.

Pros And Cons of putting old installation over new

If your old insulation is in good condition and meets the criteria discussed above, having new insulation placed over the old will save time, money, and energy. If you determine that your old insulation needs to be removed, that can be quite costly, especially if you have vermiculite insulation that may contain asbestos.

Other Considerations

An insulation installer pouring fiberglass insulation over old insulation on the attic

The most common types of attic insulation are rolled insulation (also called batt) and loose-fill insulation made of cellulose or fiberglass that is blown into place with a machine. Typically the loose-fill insulation delivers better coverage and is more affordable than the batt.

When installing new insulation over the old, you are not limited to using the same type of insulation that is already installed.  You can add loose-fill over batt, or you can put batt insulation over loose-fill. In the latter case, make sure the new insulation does not have a vapor barrier on it – also called faced insulation. This is a paper or foil type of barrier that is designed to keep moisture in.  You do not want this when installing over old insulation as it could lead to an accumulation of moisture which could cause mold and/or mildew.

For more information about picking the right attic insulation, check out the article What Is The Best Insulation For Attics?

Will Adding More Insulation Make A Difference?

Adding more insulation will definitely make a difference, provided that you are sure you need more. To determine this, do a visual inspection of your attic. If you can see the floor joists, you need to add more insulation. If the current insulation is not evenly distributed, you should add more insulation.

To determine how much insulation you need, use the standard of measure for insulation: the R-value. Typically, the recommended R-value for an attic can range from R30-R60 depending on what region you live in. Check out the map of the United States R-value and you will see the country is shown in 7 different color-coded zones. Locate the zone number for where you live and look up in the corresponding table to find what the recommended R-value is for your region.

An R30 R-value is about 10 inches deep, and an R60 R-value is about 16 inches deep.  If your current insulation does not meet the recommended R-value for your region, adding more insulation will save you money and energy.

Should You Insulate The Attic Ceiling?

A man installing roof insulation layer over old insulation layer of attic

If your attic is finished, you will want to insulate the underside of the roof. If it is unfinished but you have air circulation in your attic space, you should insulate the attic ceiling. Make sure that you maintain proper ventilation for your roof to avoid an accumulation of moisture. The space in your attic needs to permit continuous flow – hot air in the summer and cold air in the winter.

How Often Should Attic Insulation Be Replaced?

Both loose-fill (fiberglass or cellulose) and batt insulation are made from recycled materials, so they can start to degrade in 15 years. Other than that, batt insulation will usually last from 20-30 years. The loose-fill (fiberglass or cellulose) insulation can also have a lifespan of 80-100 years. If you notice any of the following signs, you will want to consider replacing your insulation:

  • Your house is drafty
  • Your heating or cooling bill has gone up unexpectedly
  • The house does not maintain an even temperature
  • There is noticeable moisture in your attic or on the insulation itself
  • You see areas where the insulation is falling down
  • You find evidence of a rodent infestation

A yearly inspection of your attic insulation is recommended by the U.S. Department of Energy. Also, if you experience a leaky roof, you should have your attic insulation inspected for water damage. In some states, energy companies may provide a rebate in exchange for proof that you have insulated your attic.

In Closing

Regulating the temperature of your home through proper insulation is an important part of homeownership. Installing new attic insulation over old is possible, provided it is done correctly according to the guidelines outlined above. A properly insulated attic will help to keep your home warm in the winter and cool in the summer, thus saving energy and money!

Before you go, be sure to check out these other HVAC guides that may be of interest to you:

How Much Does It Cost To Insulate A 1200 Sq Ft Attic? 

Is Exposed Insulation In A Basement Dangerous?

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