Basics of Insulation - Residential

When you think insulation, you’re well on your way to reducing energy costs. Adding glass mineral wool insulation above minimum building requirements significantly increases energy savings, and enhances the overall quality of your indoor environment.

Begin saving today.

If you’re a homeowner, insulation can cut your monthly utility bills by up to 48%2 and add to the resale value of your home. For commercial buildings, the savings can also be significant.

Why Insulate?

It may be out of sight, in your walls or attic, but fiberglass insulation is a critically important building material for your home. That's because it's one of the most thermally efficient and cost-effective ways to save energy while making homes quieter and more comfortable to live in. Made from recycled and renewable resources, fiberglass insulation is also a sustainable building product—one that has a positive impact on our environment, helping reduce energy consumption and the effects of global warming. Though it's been used successfully for decades in homes worldwide, fiberglass insulation is still the state of the art when it comes to energy efficiency, delivering maximum R-value performance in standard wood-frame construction.

Saving BTUs-by the billions.

A Harvard study found that by insulating the over 1.2 million new homes built each year to current International Energy Conservation Code levels, the country would save well over 300 billion BTUs over ten years. At the same time, increasing insulation in existing housing stock could save more than 800 trillion BTUs each year.

A more comfortable indoor environment.

Upgrading home insulation levels is not only a good way to help lower monthly utility bills, it adds to the overall comfort in your home. Insulation helps maintain a consistent temperature by reducing air leakage and resisting the flow of heat. Properly insulating your home not only saves money, but also will help reduce drafts and create a comfortable temperature inside no matter what the weather is outside.

More peace and quiet!

In addition to greater energy-savings, fiberglass insulation delivers excellent sound absorption. When installed between walls and in ceilings, glass mineral wool insulation significantly reduces the transmission of sound from other rooms or from the outside.

For example, installing 3-1/2 inches of acoustical glass mineral wool batt insulation between a 2x4 wood stud wall with 1/2 inch gypsum board absorbs and dampens sound waves resulting in a significantly better sound rating, improving STC (Sound Transmission Class) rating by 3 to 11 points, a significant and discernable difference. The best time to add acoustical insulation is when a new home or addition is built. Ask your builder for details about insulation upgrades.

Environmental sustainability.

As insulation saves energy it significantly decreases the generation of harmful air pollutants to the atmosphere. In fact, according to a Harvard study, insulating homes to even modest 2000 International Energy Conservation Code levels would reduce hundreds of thousands of tons of nitrous oxide and sulfur oxide released into the atmosphere each year.

Not only does glass mineral wool insulation contribute to cleaner air, it is an inherently "green" product in terms of assessing its environmental impact over its lifetime. Manufactured with recycled and renewable resources, every pound of insulation ultimately saves twelve times more energy than it takes to produce it. So along with greater energy savings, insulation delivers a measurable impact on our environment, reducing the amount of energy consumption and pollution.

Insulation also prevents the depletion of our natural resources. Today's glass mineral wool insulation contains a minimum 50% recycled glass and uses renewable resources such as sand. In fact, according to the Glass Packaging Institute, fiberglass insulation is the largest secondary market for recycled glass containers.

Types of Insulation

The two primary types of glass mineral wool insulation for your home are blanket and loose fill.

Glass mineral wool blanket insulation is packaged in batts or rolls and comes in various R-values or thicknesses. Blanket insulation also comes in various widths and lengths depending on which area of your home you plan to insulate.

Glass mineral wool batts and rolls are most commonly installed in the sidewalls, attics, floors, crawl spaces, cathedral ceilings and basements of homes. Both batts and rolls are available with or without a facing. The facing material is generally applied toward the ‘warm-in-winter’ portion of the home to help resist the movement of moisture vapor to cold surfaces where it can condense. Be sure to check your local building codes for the correct vapor retarder placement.

Glass mineral wool loose fill insulation is designed to be blown-in to attic spaces or other areas of the home that are hard to access with blankets, batts or rolls. Along with providing excellent coverage and thermal protection in hard-to-reach areas, loose fill must be installed by a professional installer using a blowing machine to assure proper coverage and long-term performance.

Want to learn more? Download the DOE Insulation Fact Sheet. It offers helpful advice on insulating your existing house and supplies information you need to know if you are building a new home.

Installation Tips--Residential Construction

Here are a few things to think about before you install:

  • Leave glass mineral wool insulation in its packaging until you're ready to use it. Packaged insulation is highly compressed and expands greatly when the package is opened.
  • Use continuous rolls in floors because of longer joist spans.
  • To cut insulation, lay it on a board with the kraft or foil facing down, if applicable. Lay a  measuring stick over the area of insulation to be cut. Press your straight edge down hard and cut with a utility knife, using the straight edge as a guide.
  • Do not compress the product when you install it. The insulation should be in full contact with the studs or drywall on all sides and the front and back.
  • Avoid leaving any gaps around the edges or around pipes or wiring.
  • Look for specific guidance when installing insulation around pipes and wiring.
  • Do your homework to see if you need a vapor retarder.

How do I know if you need more insulation?

Checking your home's insulation is one of the quickest ways to start saving energy and cutting heating and cooling costs. Follow a few simple steps to see if you need more insulation:

  • If your home was built before 1980. Only 20% of homes built prior to 1980 are well insulated.
  • If you are uncomfortably cold in the winter or hot in the summer. Adding more insulation creates a more uniform temperature, and increases comfort.
  • If you're building a new house or addition, or installing new siding or roofing, it's a lot easier to access the areas that need insulation.
  • If you notice your energy bills seem to be steadily rising.
  • If you're bothered by noise from the outdoors-insulation helps to muffle sound.
  • If you are concerned about the effect of energy use on the environment.

Also according to the DOE, the easiest and most cost-effective way to insulate your home is to save energy. To find out if you have enough attic insulation, measure the thickness of insulation and determine the R-Value.

Where should I add insulation

Think about insulating other areas of your home such as:

  • basement walls
  • floors above vented crawl spaces
  • cathedral ceilings
  • floors over unheated garages or porches
  • knee walls
  • in between interior walls (especially bathrooms)
  • ceilings or floors for extra sound control

How much insulation is enough?

Insulation is measured in R-values. So, the higher the R-value, the better your walls, floors and ceilings will resist the transfer of heat. The amount of insulation you need depends on where you live.

Glass mineral wool residential building insulation products come in R-values ranging from R-8 to R-38 for fiberglass batts and rolls. Fiber glass blowing insulation can also be blown in an attic to nearly any R-value. You’ll find the R-value of your insulation printed on the package or bag it comes in. R-values are also printed on the facings of fiber glass batts and rolls.

Insulation Pays

As energy prices continue to rise, it pays to insulate—in more ways than one. Adding more insulation to your home or building can put money in your pocket.

In addition to lower utility bills, according to the EPA, for every $1 homeowners saved on annual fuel bills due to energy-efficient home improvements, their home's value jumped by $20 or more.

Some local governments and many utility companies offer consumers cash incentives for simply upgrading their insulation.

Lower Mortgage Payments

Planning on financing a new home? Consider an energy-efficient mortgage to help offset added construction costs due to energy improvements. The benefits include:

1.    Allowing borrowers to qualify for a larger mortgage as a result of energy savings
2.    Reduced monthly operating costs
3.    100% of energy improvements can be financed—up to 15% of the value of the home for existing homes and 5% of the home's value for new construction

For more information on Energy Efficient Mortgages, visit

2Your fuel savings from insulation will depend upon the climate, the type and size of your house, the amount of insulation already in your house, and your fuel use patterns and family size.