Right Type of Insulation for the Attic

While this isn’t a question that keeps people up at night, it is a good question to know the answer to if you want to keep your house comfortable and your utility bills low. There are actually several different factors that will help to determine the right type of insulation for your attic. Let’s look at some questions to ask and examine the different types of insulation.

Here are some questions to ask when determining the right type of insulation for your home.

• Is there insulation already there and what type is it?
• Is it really old or filled with pest droppings?
• What kind of space is available to install the new insulation?

If there is already insulation there and it’s not infested with pest droppings, my advice is to go with what’s already there. Now even this has a caveat to it because if the existing insulation is fiberglass batts installed between the ceiling joists, placing more batts on top is not a good idea. It is very difficult to install batts perfectly to avoid gaps which cause the new batts to be ineffective. If it is infested, you’re better off having it removed and having all new insulation installed.

The most common types of insulation used in attics today are:

• Fiberglass
• Cellulose
• Open Cell Spray Foam

Fiberglass insulation is made from the same components used to make glass as well as recycled glass. Blown fiberglass has an R value of 2.3/inch, so if you have 12”, you have R-28. The “fluffiness” factor is part of the R-value of fiberglass, so as it settles, it loses R-value. It can be blown over existing cellulose insulation.

Cellulose is made from shredded recycled newspaper that is treated with a fire retardant and borate to discourage pests. Cellulose insulation has an R-value of 3.6/inch, so if you have 12”, you have R-43. Cellulose is much more dense and does not rely on “fluffiness” as a factor. However, because of its density it’s much heavier and adding too much can cause the sheet rock nails in your ceiling to pop.  Do not blow cellulose on top of fiberglass.

Special Note: Neither form of blown in insulation stops air flow, so before having any added, make sure all the penetrations, chases, and dry wall seams are sealed with a spray foam product to stop air flow between the attic and living space. Air flow greatly reduces the effective R-value of insulation.

Open Cell Spray Foam is a urethane based expanding foam product () that is sprayed to the underside of the roof deck usually to a depth of 5 ½” or R-21. Spray foam is a premium insulation product because it out performs all other forms of insulation because it creates a continuous air and thermal barrier.  It also comes with a premium price tag.

So, if you’re more budget conscious and have existing insulation, you will probably want to stick with adding blown in fiberglass or cellulose. Just make sure to have the air sealing performed. If you want to use your attic for storage, have HVAC equipment and ducts present in the attic, or are willing to make the investment, then spray foam is the way to go.

If you have more questions or want more information, please enter it below, email me at JonL@theNRGguy.com, or go to my Facebook page. As always, "Don’t throw money at your problems, throw knowledge, it’s a lot cheaper."