When adding additional insulation, you do not have to use the same type of insulation that currently exists in your attic. You can add loose fill on top of fiberglass batts or blankets, and vice-versa.
In general, either batt or rolled insulation or blown loose-fill insulation (fiberglass or cellulose) can be installed on top of old insulation. If you need to add new insulation on top of old insulation please note the following: Draftproofing should be completed prior to the addition of more insulation.
Adding insulation to the attic is generally a moderately difficult do-it-yourself (DIY) project, but the benefits can be substantial. If you are doing a major home renovation project, now may be a great time to tackle this project too.
Mold and Mildew Growth
Having too much insulation in your attic can allow for the accumulation of moisture. This leads to mold and mildew growth, which can be extremely bad for your health.
You should install two layers of insulation in your attic; wood joists must be covered to allow the air to move. The first layer will sit between the joists, and the second layer will run perpendicular over the joists. The first layer should have the facing against the drywall to act as a vapor barrier.
Doubling the thickness of insulation will double the insulation's R-value, cutting heat loss in half. Each time the insulation layer is doubled in thickness, this rule applies.
Easier to heat and cool: When you have quality attic insulation, more heat stays in your home through the winter, and less radiates down from your attic in the summer. This resistance to heat makes it more affordable to heat or cool your home to the temperature you're comfortable with.
Insulation levels are specified by R-Value. R-Value is a measure of insulation's ability to resist heat flow. The higher the R-Value, the better the thermal performance of the insulation. The recommended level for most attics is to insulate to R-38 or about 10 to 14 inches, depending on insulation type.
While it may seem like the more insulation you have, the more energy-efficient your home will be, you do not want to insulate both the attic floor and ceiling. Insulating the floor and the ceiling would create a separate and conditioned environment, especially if you air-sealed your attic.
If your attic has little or no existing insulation, you'll want to install an R-38 rated material. If your attic has 2-3″ of existing insulation, you'll want to install an R-30 to achieve a total of R-38. If your attic has 5-6″ of existing insulation, you'll want to install an R-19 to achieve a total of R-38.
Removing old insulation is generally recommended if it's damaged, contaminated with mold, or infested with pests. However, if the insulation is in decent shape and just needs a boost, adding a new layer on top can be a cost-effective option.
Provided the existing rolls are in good shape, you can absolutely retrofit batt insulation with blown-in insulation! Materials can even be mixed, such as blowing in cellulose insulation on top of fiberglass batts (or vice-versa).
Cons of Blown-In Attic Insulation:
Poor installation can lead to uneven coverage, material waste, and even structural issues like sagging ceilings. Hiring a skilled installer is crucial to getting the most out of this insulation type.
Yes, adding insulation to your attic can help regulate the temperature in your home and prevent it from losing heat, lowering the energy needed to heat it. It may cost some money upfront, but you'll save money in the long run with lower energy bills.
Too much insulation will leave humidity and moisture to accumulate in your attic space. This can lead to mold growth on your walls and insulation. There might also be water damage to the support beams in your home's roof.
Can I put plywood over insulation in the attic? Yes you can install plywood subflooring directly over the floor joists and insulation on your floor. You need to install rigid insulation boards on top of the attic flooring joists and then install plywood over the top.
Insulation is graded by its R-value—the higher the R-value, the greater the insulating power. If you live in a mild climate, your attic should have a minimum grade of R-38, or about 13–14 inches of insulation. If you live in a colder climate, R-49 is the minimum recommendation, or about 16–18 inches of insulation.
If your insulation levels are more than 4-6 inches below the recommended level (or your attic floor joists are not buried) you should consider adding more to improve the comfort and energy efficiency of your home.
Blown-In Insulation (Fiberglass And Cellulose)
In most homes, loose-fill insulation can survive anywhere from 80 to 100 years before needing replacement, provided that it is not damaged.
Best Time of Year to Buy Insulation
In this case, the spring is the best time, because you will also start to see savings in the summer months. The same is true for warmer climates, just different times of year because you'll want the job finished before the heat sets in.
Fiberglass batt is considered to be the best insulation for attics. Compared to other insulation materials, it is the cheapest and easiest to install. Fiberglass batt is also incredibly energy efficient, as it helps to slow the spread of hot and cold air.