Insulation That Has Settled
You may be wondering if you need to replace insulation that has settled. Even if your existing insulation has settled, you can leave it in place and simply have insulation added on top of it (as long as it does not have any of the previously mentioned deficiencies). Insulation that has settled still has thermal resistive properties that add to the overall R-value once new insulation is added.
By leaving the old insulation intact, you are also leaving the original vapor barrier intact, as long as it was installed properly during the original installation. However, air sealing the attic floor with fireproof foam will need to be done before new the insulation is installed to increase efficiency and prevent moisture from inside the house.
If you have fiberglass batts in your attic, there is a good chance there is already a vapor barrier, as most of these batts have a thick piece of heavy-duty paper on one side, specifically designed to act as the vapor barrier.
For blown-in fiberglass insulation, you should see a plastic membrane or other vapor impermeable material installed to help stop the exposure of moisture to your insulation. Moisture will reduce the R-value (a measure of thermal resistance) of your insulation over time. This is another reason it is important to have a professional inspect your attic to ensure your vapor barrier is not damaged or missing.
When using blown-in cellulose insulation, a vapor barrier is not needed as it acts as a natural vapor barrier and will restrict the flow of vapor in the attic. It is always important to make sure the attic is properly ventilated to decrease moisture build-up. In some cases, it may be necessary to add supplemental ventilation in the form of an attic vent/fan.
For new construction and situations where insulation needs to be removed, a professional should air seal with fireproofing foam at all of the gaps in between the drywall and the framing members in the attic. After the gaps are sealed, they will install the baffle for proper ventilation and install up to 16-18 inches of cellulose to get an initial R-value of R60.
All insulation will settle, so an experienced professional will know to compensate for the settling by installing an extra 2 inches of cellulose insulation. Extra insulation will also be valuable in any future work that needs to be done in the attic as it can be disbursed to the areas that are worked on.
What Type Of Insulation Should You Use After Insulation Removal? Add Blown-In Insulation Will Be The Best Choice
Blown-in insulation is a great option as it covers the area more effectively than bat fiberglass. A professional will blow in the material through a 3-inch hose and completely cover the attic floor, encapsulating the ceiling joists. This is important because wood has a low R-value, meaning it transfers heat very easily. By encapsulating the floor joist with insulation, thermal bridging (the transfer of heat) is eliminated making the insulation more effective.
The most common types of blown-in insulation are fiberglass and cellulose. Cellulose is a great alternative to blown-in fiberglass insulation because it is healthier, eco-friendly, and will resist mold growth while having similar, if not greater thermal resistive properties (higher R-value) than blown-in fiberglass insulation.
Cellulose insulation is also a natural vapor barrier and will save you on the additional expense of removing insulation. Blow-in fiberglass is made out of rigid fibers and doesn’t stop the moisture or air leaks. Blow-in fiberglass also requires a continuous moisture barrier.
Spray Foam Removal
Although spray foam insulation is popular and applicable in many situations (such as commercial metal roofs), there can be serious problems if it is not applied properly. Even when it is applied properly, there are many situations where spray foam is not the most appropriate product to be used on the attic rafters. Many spray applied foam insulations pose fire hazards and make it hard to identify roof leaks since spray foam is applied to the underside of the roof decking.
If your foam insulation in the attic smells bad, it may have been applied at the wrong temperature, installed too thick, or not applied properly at the time of installation. Another cause for complications with spray foam in the attic is roof leaks. Spray foam insulation can cause the water to be trapped between the foam and the roof decking, creating a potential for the roof decking material to rot. It is imperative to have it removed and replaced if there has been water damage.