Blowing insulation into an attic space is a remarkably simple home energy retrofit project that can have truly enormous financial and energy saving payback. Insulation is one of the cheapest components of a home, yet has the largest potential for saving money over the course of the life of a building.
In fact, many insulation projects have an energy savings payback of less than a single year. That means that you may see enough savings in energy bills in a single year to pay for the cost of installing new insulation. Every year afterward, that savings is money in your pocket.
Blowing Insulation: Where to Insulate
One of the most common questions I hear from homeowners is regarding what home energy retrofit project will have the most impact for the money.
The easy answer is that, for most buildings, attic insulation is the no-brainer project that nearly every homeowner should undertake (although many buildings could also benefit from plugging air leaks, but more on that another time).
For homes with a cold-roof design, that is, homes with a blanket of insulation on the floor of the attic space, beefing up that insulation can greatly improve both heating and cooling energy loads for the home.
If your insulation in on the underside of the roof, the following insulation upgrade may not be appropriate for your home. Consult an energy auditor to determine the best way to upgrade the insulation in these homes.
During the heating season, a thick blanket of attic insulation acts like a hat for a home. As we know, heat rises and tends to escape through the top of a home. Insulation slows the loss of heat to the outdoors.
During the summer season, an attic space can become a sweltering sauna. Good attic insulation limits the amount of heat that radiates into the living space of your home.
What Kind of Insulation?
You may find one of more of several different types of insulation in your existing attic space, each having their own strengths and weaknesses.
The most common type of insulation found in many homes is fiberglass batt. This basic method of insulating is inexpensive and easy to install, but is often poorly installed and almost always too thin to effectively insulate a home.
My favorite attic insulation upgrade is blowing insulation over the existing insulating blanket using a power blower. Blown-in insulation products, also called loose-fill, when installed correctly, can fill cracks and gaps in the existing insulation blanket and can cover framing members to further limit thermal transfer between the attic space and the living space of your home.
Loose-fill materials include fiberglass, mineral wool, rock wool, slag wool, or cellulose. The two most common varieties used today in many areas are loose-fill fiberglass and paper cellulose.
For the do-it-yourselfer taking on an insulation upgrade, I really like blown-in cellulose.
Cellulose is truly a green product. The material is locally produced in many areas, contains 80% or more recycled content, and is largely non-toxic.
If you look closely at cellulose insulation, you’ll quickly realize that this stuff is actually finely chopped newspaper and telephone directories. You can often still see the printing on the tiny bits of paper.
Cellulose is treated with a natural non-toxic borate product that makes it fire and mold resistant and very undesirable to insects or rodents.
At an R-value rating of 3.75 per inch, cellulose often has a higher R-value than fiberglass batts and is especially good at filling in areas that are extremely difficult to insulate with other products.
Many insulation suppliers will loan or rent installation blowers to homeowners. The job is very dusty, but not particularly difficult.
Ask your supplier for a quick check-out on the blower you will be using. You will need a helper to load insulation bales into the blower hopper while the other person directs the blower nozzle in the attic.
Ventilation helps control moisture in the attic space so you don’t want to impede the existing ventilation openings in any way. If you have insulation on the underside of your roof, you will not have attic ventilation.
The downside of loose-fill cellulose insulation is that paper readily absorbs moisture and is slow to release that moisture. Roof leaks can mean removing and replacing any wet insulation. In areas with extremely high summer humidity levels, such as the southeast US, cellulose may not be a the best choice as the material can absorb a lot of water directly from hot moisture laden air.
Blowing Insulation: How Much Is Enough?
The following US Department of Energy map shows the local insulation zone for your area and the corresponding recommended insulation level for that zone.
|Zone 1: R-30 to R-49||Zone 4: R-38 to R-60||Zone 7: R-49 to R-60|
|Zone 2: R-30 to R-60||Zone 5: R-38 to R-60||Zone 8: R-49 to R-60|
|Zone 3 R-30 to R-60||Zone 6: R-49 to R-60|
Also see the US Department of Energy Guide to Blowing Insulation.
About the Author:
David Arthur, LEED-AP, Energy Auditor and green building consultant is an admitted green building nerd. He gets quite animated about such subjects as the embodied energy in concrete and window emissivity. He operates the website GreenHomesConsultant.com.