How long does it take cellulose insulation to settle?

Author: Priscilla Weissnat  |  Last update: Friday, June 6, 2025

For example in an attic insulated to R49 (R-Value) the cellulose insulation material will settle about an inch and half. Industry, as well as internal Fiberlite research, suggests this occurs within the first 48-72 hours after the material is installed into an attic.

How to keep cellulose insulation from settling?

The only way to prevent this is to dense pack during install. The only way to fix this is to add more cellulose. The most cost effective thing to do is to DIY.

Does cellulose insulation compact over time?

Factors Influencing Lifespan of Cellulose Insulation

Firstly, if the insulation is not installed correctly, it may settle and compact over time, reducing its effectiveness. Second, low-quality cellulose insulation may not withstand the test of time and perform efficiently for as long.

Does wet blown cellulose settle?

It relies on the 'fluff' of its fibers to create a seamless thermal barrier. However, when saturated with water: The weight of the fibers increases significantly. This added weight causes the material to compress and settle.

How much does blown-in cellulose settle?

Cellulose insulation can settle by as much as 20 percent, depending on how it is installed.

Is Adding Attic Insulation Really Worth It? | Results from a Real House

How long does it take for cellulose to settle?

For example in an attic insulated to R49 (R-Value) the cellulose insulation material will settle about an inch and half. Industry, as well as internal Fiberlite research, suggests this occurs within the first 48-72 hours after the material is installed into an attic.

What are the problems with blown-in cellulose insulation?

According to the home restoration experts at SeviceMaster, one blown-in cellulose becomes wet, it becomes very heavy, and difficult to clean. Even a small area of water-damaged blown-in cellulose may require completely re-insulating the area.

How long does cellulose insulation take to dry?

How long does it take for the spray applied cellulose to dry? Depending on atmospheric conditions, you should wait 3-5 days after installation before hanging sheetrock. Cellulose dries from the face back towards the sheathing and loses 1/2 it's moisture in the first 24 hrs.

Can mold grow on cellulose insulation?

In addition to losing effectiveness, wet cellulose can also encourage the growth of mold and mildew, contaminate your indoor air with mold spores and lead to structural problems as wood framing begins to rot.

What is a disadvantage of cellulose insulation?

Cellulose insulation is heavy, and compacts any underlying insulation. Because cellulose insulation is paper, it absorbs moisture when it rains, and in areas of high humidity. Cellulose insulation degrades over time and has to be replaced. Cellulose insulation promotes the growth of mold & mildew in your attic.

Will mice nest in cellulose insulation?

Rodents generally are not drawn to cellulose insulation, either. This is because it's loose and tends to fall in on itself. It's not ideal for burrowing and building a nest. You can pretty easily install cellulose yourself, but you have to rent a special machine to blow it into the walls of your attic.

Can you put in too much cellulose insulation?

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.

What is the life expectancy of cellulose insulation?

Because it is made primarily of recycled materials, however, cellulose insulation does degrade over time. The typical lifespan is 20 to 30 years, with degradation beginning as early as 15 years after installation. As with other types of insulation, severe weather or outside interference can reduce the lifespan.

Does cellulose insulation need a vapor barrier?

Do I need a Vapor Barrier? With cellulose insulation, a vapor barrier isn't recommended except in cases of high humidity areas, such as rooms with indoor pools and spas.

Does dense pack cellulose settle?

Dense-packed cellulose doesn't settle, because it can't. It's installed at twice its settled density, which means that it's under slight pressure in the wall or ceiling cavity.

What happens if cellulose insulation gets wet?

Cellulose Loose-Fill Insulation

Because this type of insulation features plant fibers, that means it can pick up moisture like a sponge. If a small section of the insulation is wet, you might be able to get away with replacing only the affected area. It might also be possible to dry it out.

How long does it take for insulation to settle?

In fact, cellulose has the highest rate of settling rates, ranging from 13 to 20% after installation. This settling continues for weeks, months, and years after installation, and if not addressed properly during the insulation, it can cause serious energy efficiency issues.

How thick should cellulose insulation be in attic?

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.

Does cellulose insulation make your house dusty?

While it may be one of the oldest materials, cellulose can still have a number of issues ranging from dust getting all over your home to the material settling leaving areas uninsulated.

Is it bad to breathe in cellulose insulation?

Unlike glass fibers, cellulose isn't dangerous to breathe. However, it can irritate your lungs. If you have pre-existing allergies, the dust of cellulose insulation can be obnoxious.

Which is better, attic insulation blown or rolled?

Blown fiberglass insulation scores an R-value of 3.2 to 3.8, making it slightly less likely than rolled fiberglass to prevent the flow of heat into and out of your house. That being said, though, blown fiberglass insulation isn't meant to cover huge areas like rolled fiberglass insulation.

Should I remove old attic insulation before adding new?

Do I Have To Remove Old Insulation? Unless your insulation is wet, moldy or infested with pests, you don't need to remove it before adding insulation on top of it. ENERGY STAR® recommends that you inspect your insulation for signs of mold, mildew, moisture and pest infiltration before making this determination.

How much does it cost to insulate a 500 square foot room?

Fiberglass batt and roll insulation can cost from $1,000 to $2,400, with an average cost per square foot of between $0.30 to $1.50. If you have a 500-square-foot area, and you do the job yourself, you're looking at spending about $150 to $700.

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