Back to blog

All About Attic Insulation

BRAX Roofing gaithersburg

Many homes in Maryland, Washington, DC, and Virginia were constructed at a time when energy costs were low, and concerns over carbon emissions were unheard of. As a result, many residences have inadequate attic insulation. As utility rates increase, the cost of having insufficient insulation rises as well.

It is also important to consider the other benefits of adding new insulation to your attic. Today’s products also provide beneficial sound, fire, and mold resistance as well.

The Case for Increased Attic Insulation

Several years ago, Boston University researchers led by Dr. Jonathan Levy concluded that approximately nine of 10 U.S. homes are under-insulated. Inadequate attic insulation is often a part of the problem, particularly in homes built before modern insulation standards were established.

The Insulation Institute says, “If your home is more than 10 years old, you likely need more insulation.” In the past, insulation simply filled the gaps between joists. As a result, R-15 to R-21 insulation levels are common in older homes. Since the wood in the rafters is a relatively poor insulator, thermal bridging across the joists further reduces the insulation’s effectiveness.

Suggested R-values vary around the country, from R-30 in warmer areas to R-60 across the northern tier of states. The U.S. Department of Energy divides the country into eight climate zones. Maryland, Washington, DC, and Virginia are in zone 4, where R-49 to R-60 attic insulation is recommended. For many homes, this is the “sweet spot” where the added investment in extra insulation is cost-effective long term.

Department of Energy Recommended Total R-Values for New & Existing Homes

 The following Department of Energy zone recommendations are based on comparing estimated future energy savings to the current cost of installing insulation. The DOE gives a range for many locations for the following reasons:

  • Energy costs vary greatly over each zone
  • Installed insulation costs vary greatly over each zone
  • Heating and cooling equipment efficiency varies from house to house
  • The best estimate of future energy costs may not be exact. 1

Overview of Attic Insulation

A reputable, certified contractor is well-positioned to recommend the type of attic insulation that is ideal for your specific situation. In some homes, it is possible to simply add new insulation to the existing insulation. In other residences, it may be necessary to remove old insulation that is either wet and compressed or contaminated by mold or mildew.

There are various kinds of insulation to consider, including batts/rolls, loose fill, rigid foam, and spray foam.

Batts and rolls

This type of insulation, usually made of fiberglass, mineral wool, or cotton, comes in pre-cut widths that fit between joists with standard spacing. Some batts and rolls include a foil or paper backing that serves as a vapor barrier, while others are non-faced.

Time-consuming cutting is required for attics with lots of irregularly shaped spaces. Some things just can’t be avoided, like exhaust fans and junction boxes. Installation is also difficult in attics with smaller spaces that are tricky to access. Even the most disciplined worker may find it difficult to accurately cut each piece to size. Any gaps compromise the insulating value of the project.

Loose-fill insulation

Fiberglass loose-fill insulation is easier to install than batts or rolls because it readily flows around various obstructions commonly in attics, like ductwork and wiring. It can also be successfully blown into narrow spaces along the outer edge of the attic. Modern fiberglass insulation is manufactured from recycled glass and/or sand that is melted and spun into extremely thin fibers, giving it the consistency of cotton candy.

Three other choices are cellulose, mineral wool, and cotton loose-fill insulation. Cellulose insulation is frequently made from recycled post-consumer paper waste (often newsprint). Mineral wool (also called rock wool) is often spun from the slag generated by blast furnaces. Cotton insulation is made from recycled denim cloth. All forms of loose-fill insulation are relatively easy to install compared to

Rigid foam

Three types of rigid foam are also used as attic insulators – expanded polystyrene (EPS), extruded polystyrene (XPS), and polyisocyanurate (Polyiso). All three offer relatively high R-values per inch, with Polyiso being the highest. However, the thicknesses required to reach the high R-values may be cost-prohibitive. All three types of rigid foam typically cost more than loose-fill insulation, although EPS is the least expensive of the three. Installation expenses drive costs higher. Water-resistant XPS panels have high compressive strength, making them a more common choice for below-grade insulation of basement walls and foundations.

Spray foam

Spray polyurethane foam (SPF) comes in both open-cell and closed-cell formulations. Most SPF is a dual-component product. A and B chemicals are mixed on-site. A chemical reaction occurs, and the foam greatly expands as it emerges from a heated hose used to deliver it to the desired attic location.

Open cell foam is not air permeable, but it is water permeable. Higher-cost closed-cell foam is an effective air and moisture barrier, and it also has a higher R-value than open-cell foam. SPF simultaneously seals cracks/gaps while reducing airflow. Sometimes, a layer of spray foam is applied, followed by a much thicker layer of loose-fill insulation. The U.S. Environmental Protection Agency (EPA) has expressed certain health concerns related to the use of the product, particularly by those with certain skin sensitivities or allergies.

Potential Energy Savings

How much can you save by adding insulation? Of course, the answer to this question is unique to each home. However, it is worth noting that electricity rates run high in some parts of the Mid-Atlantic. For example, the average 12.84 cents/kWh residential electricity rate in Maryland ranks 15th in the country.

The government’s ENERGY STAR® website says, “Homeowners typically save up to $200 a year in heating and cooling costs by air sealing their homes and adding insulation.” Of course, once an attic is properly insulated with a high R-value product, energy savings accrue year after year.

It is possible to maximize your savings by minimizing air leaks with professional caulking, weather stripping, and expanding spray foam. It is also helpful to minimize air leaks around your attic door/hatch and to insulate it as well.

Sealing air leaks also limits moisture intrusion, particularly in the humid conditions encountered during the summer months. Moisture is also generated by activities in the home, like showers and washing clothes. The insulating value of both batts and loose-fill products are quickly compromised when they absorb too much moisture, so proper sealing of cracks and gaps is an important part of the job.

Other Benefits

Although the savings in heating and cooling costs are a major reason to add insulation to your attic, there are other important reasons to do so. Consider the many other benefits of loose-fill fiberglass insulation:

Noise reduction

High-quality loose-fill insulation does an excellent job of absorbing sound. Its superior acoustic performance limits distracting sounds that might otherwise make their way into your home.

Fire resistance

Loose-fill fiberglass and mineral wool insulation are both non-combustible. Since cellulose insulation is made from combustible paper products, it must be treated with large amounts of fire-retardant chemicals like borax nitrate, boric acid, and/or ammonium sulfate to meet fire standards. In fact, cellulose insulation is an estimated 15% to 20% fire retardant by weight.

Moisture resistance

Since the R-value of insulation is quickly compromised when it gets wet, moisture resistance is of utmost importance. Since moisture can be trapped in fibrous insulation like fiberglass, it is important to ensure proper airflow through proper venting. Fortunately, the material possesses excellent air permeability, so moisture will quickly evaporate if provisions are made for good airflow.

Mold resistance

Given the increased awareness of the potentially damaging effects of mold, it should come as no surprise that mold-resistant building products are quickly gaining favor. One of these is loose fiberglass insulation. It is naturally mold resistant, in part because it is non-organic. Mold needs nutrients (organic matter), moisture, and certain temperatures to grow. Properly sealed air leaks reduce moisture intrusion. Good airflow further reduces moisture, which more readily evaporates from the spun fiberglass.

Minimize ice dams

As the Insulation Institute notes, an uneven flow of heat into the attic can make ice dams worse. These icy accumulations occur as melting snow on the roof re-freezes as it approaches the colder outer edge of the roof. The resulting ridge of ice is commonly referred to as an ice dam because it prevents the proper drainage of water. Water backed up behind ice dams can find its way into the sub-roofing, framing, and/or interior living spaces. Proper sealing and insulating of your attic space minimize this potentially serious problem.

Less strain on the building

Loose-fill fiberglass insulation weighs less than alternatives like cellulose. When you want to achieve high R-60 values, the overall weight of the insulation may be a factor in some residences.

Recycled materials

Although cellulose insulation has traditionally featured more recycled content than its fiberglass counterpart, the latter is posting steady gains in this category. For example, SCS Global Services certifies that Pro Cat fiberglass insulation from Owens Corning averages 55 percent recycled content.

Advantage at resale

It is a good selling point to be able to tell a buyer that you installed R-60 insulation in your attic. A well-insulated home may also be easier to sell because of the lower utility bills you can show a buyer. Also, many prospective buyers understand that a well-insulated roof enhances the comfort of the home’s occupants.

Importance of Proper Installation

As with most home improvement projects, it is necessary to prepare the attic before adding more insulation. It is also important to have skilled technicians do the work to maximize effectiveness.


Before blown-in insulation is added, a careful examination of the existing insulation is necessary. Old batts may exhibit water damage, and some may even be moldy. These damaged batts need to be removed, or the new insulation project will be compromised. Older insulation may also lose its loft and, therefore, some of its insulating capacity. Sometimes, it is best to simply remove the old insulation. This also makes it possible to locate and seal air leaks before a thick layer of loose-fill insulation is installed in your attic.

Some pre-1990 homes have attics insulated with vermiculite, a lightweight, grainy substance sometimes obtained from mines with asbestos deposits. Vermiculite needs to be tested to determine if it is tainted with asbestos. If it is, professional removal is required before the new insulation is blown in.

Importance of baffles

Insulation baffles, also known as rafter vents, enhance the performance of attic insulation. They are positioned between the rafters where the attic floor and ceiling meet. They typically come in four-foot lengths. Varied widths accommodate different rafter spacing. They are usually stapled to roof decking before the insulation is installed.

The use of baffles ensures that soffit vents remain clear, and they provide channels for air to properly flow from the soffits to the ridge vents. The baffles make it possible to position insulation all the way to the outer edge of the attic floor.

As with virtually all home improvement projects, successfully insulating an attic requires expertise and self-discipline. Professional installers need to use appropriate safety procedures to avoid inhalation of fiberglass particles during installation.

Installers must be alert to air leaks that need to be sealed. Second, if insulation is blown into the attic, it must be applied at a consistent depth to maximize its effectiveness. Careless or shoddy procedures can seriously compromise R-values, reducing future energy savings in the process.

Warranty Coverage  

When you add insulation to your attic, you want the peace of mind that comes with a solid warranty from a major manufacturer that will be there to back it up. For example. A Limited Lifetime Warranty from Owens Corning provides added peace of mind when its Pro Cat fiberglass insulation is installed.

Tax Credits

federal tax credit is available to partially offset the cost of adding insulation to your attic. The tax credit is 10 percent of material costs, up to a maximum of $500. Many kinds of attic insulation qualify, including blown-in fiberglass insulation, batts, rolls, rigid foam, and expanding foam. Keep in mind that a federal tax credit is subtracted from your federal tax bill.

Contact Us Today

BRAX Roofing uses the ProCat professional loosefill insulation system from Owens Corning, an iconic American company. ProCat insulation is an Energy Star-certified product. Products with the ENERGY STAR® certification save energy and protect the environment without sacrificing performance.

BRAX Roofing offers DMV homeowners complete roofing and attic insulation services. BRAX is certified by a number of building materials manufacturers. For example, we are an Owens Corning Platinum Preferred Contractor, a designation fewer than one in 100 companies achieve.

To learn more about how adding attic insulation can cut energy costs, reduce common attic problems and improve comfort, please contact us today!

Schedule Your
Free Estimate


Our Coupons


With any full roof replacement

20% off

With any full roof replacement

Free shingle upgrade

Any full roof replacement

Roof replacement must be $10,000 or greater

$1,500 off

  • House BG

    Contact Us for a Free Estimate

    Contact Us for a Free Estimate

    What to Expect When
    You Choose Our Team

    We’re Committed to You
    Every Step of the Way
    • Meet to discuss your project and free estimate.
    • Select materials and colors for the look you want.
    • Arrange payment through financing or your insurance.
    • Install new roofing, siding, or gutters for amazing results.
    • Ensure you’re 100% satisfied with our services.
    BRAX roofing contractor wearing safety gear while installing new residential roof