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How Much Does Blown-in Insulation Settle?

How Much Does Blown-in Insulation Settle?

August 22, 2019

You may have heard a rumor that blown-in insulation can settle and reduce the effectiveness of your insulation. Luckily, these rumors are only partially true. Blown-in insulation can settle, but only under certain conditions, with certain materials, and with certain installation techniques.

If you are considering blown-in insulation, it is important you know the advantages and disadvantages of each insulation material. That’s why the technicians at DFW Thermal have put together this guide to blown-in insulation.

What is blown-in insulation?

Blown-in insulation refers to the method through which insulation is applied to an attic, wall, or crawlspace. Cost-effective insulation batts come in large squares that are unrolled. Spray foam insulation is applied with a specialized spray gun. But blown-in insulation is ejected out of a large hose with plenty of aeration. When certain materials are blown-in, they will eventually lose aeration and settle. However, any insulation technician worth their salt will know how to avoid settling.

What materials can be blown in?

Several insulation materials can be blown in. Each material has specific advantages and disadvantages.

Fiberglass – Fiberglass insulation is made of small, thread-like pieces of glass that, together, form a soft mass. If not installed using proper safety equipment, fiberglass particles can be breathed in and lodge in the lungs, potentially causing cancer.

Cellulose – Cellulose insulation is made of recycled newspapers and cardboard. It is coated with chemicals to make it moisture-resistant and fire-retardant.

Mineral Wool – Mineral wool insulation is made from stone or waste from steel mills (slag). Like fiberglass, the particles in mineral wool insulation are thread-like and form a soft mass that can be blown into walls and attics.

How much does each material settle?


It is not common for fiberglass to settle. This is largely due to its low R-value, or ability to slow airflow. Because fiberglass insulation has a low R-value, it needs to be installed in thick layers to be effective. The dense volume of fiberglass insulation prevents settling.


Cellulose insulation, unfortunately, is most likely to settle. Over time, the aeration in cellulose insulation will decrease. This settling will cause cellulose insulation to lose up to 20 percent of its R-value. Furthermore, cellulose insulation is particularly vulnerable to moisture. If your home is humid, it will accelerate the settling. Luckily, it is relatively simple to fix the issue of settling cellulose. By blowing in about 20 percent more insulation, you can account for settling.


Rockwool insulation, much like fiberglass insulation, has a lower R-value, and therefore requires greater thickness to be effective. Its large density will prevent settling.  

How much does blown-in insulation settle? Call DFW Thermal to find out more!

There are a lot of insulation options on the market. If you want to know, with certainty, what type of insulation is right for your home, call a professional. The technicians at DFW Thermal have years of experience insulating the DFW area with the highest quality materials. We are happy to answer any and all insulation questions. Give us a call at 214-731-3115 or schedule your free consultation online.