The cellulose insulation in my home's walls has settled, leaving about 1.5 ft of uninsulated top wall. How do I fix it?
The exterior walls are a Masonite-type wall board. Access is going to be difficult.
Cellulose insulation is a great product, reusing old newsprint and other recycled paper products (treated to guard against fire and insects).
This question of settling is brought up every time the topic of cellulose insulation is discussed. The material being blown in has the tendency to settle, especially in the tall volumes of wall cavities. The issue is not with the material itself but due to the installation.
- The settling of the material creates uninsulated gaps in the perimeter walls and under-insulated areas in ceilings.
- You have most likely seen an initial decrease, and then a gradual increase in your energy usage over time since the insulation was installed.
According to the Cellulose Insulation Manufacturers Association (CIMA), blown-in insulation should be installed within walls to a specific density, to protect against the settling of the product.
- If this density of the insulation is not attained, the product will settle over time.
- In a horizontal installation such as an attic floor, it is recommended that you install more insulation than the thickness required, combating the compaction of the material.
- You can get more detailed information from CIMA's technical bulletin.
Fixing the problem
The reason why the product settles is easy to see, but the repair is not. The options you have are:
- Cutting holes in the top of the wall cavity between each stud and installing more insulation. Since you have a difficult interior finish to deal with, consider that the insulation can be installed from the interior or the exterior of the building. You will have to discuss this with the contractor you retain to determine which finishes can be patched for a lesser cost.
- The most invasive option is removal of the interior finishes and the existing insulation and installing a new insulation product of your choice. This is the least economical of the options, with a long period of time before you see a return on the investment.
For more information:
Check Lily Livingston's Q&A "Doesn't sprayed cellulose insulation tend to settle, leaving areas in the wall where there is no insulation?"