Quick Answer
Yes, but it's recommended to remove existing batts insulation first for optimal effectiveness and to prevent moisture buildup. Blown-in cellulose can be added without removing the existing insulation, but this approach may not be as effective as removing the batts.
Preparing for Cellulose Installation
When adding blown-in cellulose over existing batts insulation, it’s essential to ensure air-tightness in the space. Seal any gaps or holes in the walls and ceiling with caulk or spray foam to prevent cellulose from escaping or moisture from entering. A typical cellulose installation involves a 6-8 inch layer for a R-19 to R-38 insulation rating, which can be achieved by blowing cellulose at a rate of 3.5 cubic feet per minute (CFM) through 2-inch diameter hoses.
Cellulose Over Existing Batts Installation Methods
Two common methods exist for installing cellulose over existing batts insulation. The first method, known as the ‘cut-out method,’ involves removing a section of the drywall or plaster to access the batts. Once the batts are removed, cellulose is blown directly into the wall cavity. The second method, known as the ‘add-on method,’ involves leaving the existing batts in place and blowing cellulose directly over them. For this method, a lower CFM rate of 2.5 is recommended to prevent over-insulation and ensure even distribution of the cellulose.
Post-Installation Considerations
After the cellulose has been installed, it’s crucial to ensure that the space remains air-tight to prevent moisture buildup and minimize the risk of mold growth. Check for any gaps or holes in the walls and ceiling, and seal them as necessary. It’s also essential to install a vapor barrier on the warm side of the insulation to prevent moisture from entering the cellulose.
Find more answers
Browse the full Q&A library by topic, or jump back to the topic this question belongs to.