When it comes to insulation, the R-value is a measure of its ability to resist heat flow. The higher the R-value, the better the thermal performance of the insulation. Blown fiberglass insulation has an R-value of 2.2 to 2.7 per inch, while fiberglass blocks and rolls offer an R-value of up to 4.3 per inch. The recommended level for most attics is to insulate to a height of R-38 or around 10 to 14 inches, depending on the type of insulation. Installing blown insulation in an attic is more expensive than insulation embedded in walls due to the large area of most attics and the need for two people to remove the burst insulation.
To install blow insulation on existing walls, holes are drilled at the top of each strut and the material is blown through a long, flexible hose. It doesn't require any special skills, but you'll have to crouch under the low, sloping attic beams to distribute the insulation evenly. It is also possible to remove blown insulation from an attic on your own with the right tools and protective equipment. When adding additional insulation, you don't have to use the same type of insulation that currently exists in your attic. Cellulose attic insulation should be checked for significant degradation about 15 years after it was installed. Another disadvantage of blown insulation for walls is that an obstruction in the wall space can prevent the insulation from filling the entire space of the uprights, leaving a void without insulation.
Once all of the attic insulation has been removed, contact your local waste management authority for recommendations and instructions on how to properly dispose of your specific type of insulation. It is important that the insulation is evenly distributed without low spots; sometimes there is enough insulation in the center of the attic and very little along the eaves. Not all types of blow insulation offer the same thermal value, but in most cases, even adding a little insulation is better than not adding it at all. Current building codes require a minimum amount of insulation in walls and attics, but older homes used to have insufficient insulation, so built-in insulation may be necessary. Now that you've hermetically sealed the attic and basement, it's time to check if your attic's insulation levels are sufficient and add more if needed.
