Insulation Buying Guide

The right home insulation can save on energy and heating and cooling bills

According to the U.S. Department of Energy, 50 percent to 70 percent of the energy used in homes is for heating or cooling activities. By properly insulating your home, you can create a more comfortable and consistent indoor climate while significantly improving your home's energy efficiency.

This guide will help you learn about the different types of residential insulation.

How Does Insulation Work?

Insulation decreases the amount of heat entering from outside when it’s hot, and traps warmth inside when it’s cold. The R-value indicates how well insulation resists heat transfer.

Tip: Most homes are insulated in the attic and any floors that are located above unfinished basements or crawl spaces. The most effective places to add insulation to older homes are exterior walls, attics, basements and crawl spaces.


R-Value - Insulation

R-values vary based on the type, thickness and density of the material being used. Insulation with a higher R-value will perform better than insulation with a lower rating.

Types of Insulation

The most common insulation materials are fiberglass, cellulose and foam. Insulation types include loose fill, batts, rolls, foam board, spray board and vapor barriers.

Tip: The type of insulation you need depends on which is currently installed and the required R-value.

Blown-in/loose fill

Blown-in/loose fill

  • Usually made of fiberglass or cellulose (recycled paper fiber)
  • Blown or sprayed into place with pneumatic equipment
  • Ideal for hard-to-reach areas such as attics
  • Can fill wall cavities and installed over existing insulation


  • Precut sections of fiberglass or rock wool insulation
  • Designed for easy handling and use between framing, such as studs and joists
  • Available either with or without paper or aluminum foil facing
  • Can be used in floors, walls, attics and ceilings


  • Available in pre-cut widths to fit between studs and joists
  • Come in continuous lengths ranging from 20 to 40 linear feet
  • Ideal for attics, floors and other areas where longer runs are needed

Foam board

  • Rigid panels of insulation
  • Can be used to insulate almost any part of your home, from the roof down to the foundation
  • Polystyrene and polyurethane are the most common types of materials used in making foam board
  • Sheathing reduces heat conduction through structural elements like wood and steel studs
Spray foam

Spray foam

  • Latex or polyurethane spray foam is sprayed into place with a spray can or specially designed equipment
  • Can be used to fill small gaps and cracks
  • Ideal for sealing around doors, windows and vents
  • Sets quickly and can be trimmed, painted or stained

House wraps and Kraft-faced insulation are examples of vapor barriers that help control the amount of moisture that passes through the insulation.

If moisture from either direction is allowed to build up within stud or cavity walls, the heat-conducting moisture will cause the insulation to lose its R-value and mold and rot will set in over time.

Vapor barriers are most commonly used when framing the exterior walls of a house.

How Much Insulation Do I Need?

To get an idea, check if your home is already insulated, measure the area needing insulation, and determine which type of insulation is best.

  • Determine if and where you already have insulation. If you do have insulation, find out the type and compare it to industry standards. Manufacturers determine the value by the R-value or number; the higher the R-value, the better the insulation works.
  • Calculate additional insulation needed. Measure the depth of your current insulation. R-38 is the industry standard, and the minimum thickness for R-38 is 12 inches. If your current insulation is only 5 inches deep, you will need to add 7 inches of insulation to achieve the 12-inch R-38 rating.
  • Measure the area needing insulation. Measure the length and width of the area you need to insulate. Multiply the length times the width to determine the square footage of the space.
  • Decide the type of insulation to use. Cellulose insulation is calculated based on the depth of the blown-in insulation. Fiberglass insulation is calculated based on the number of batts or rolls you need. Blown-in insulation requires the least amount of work, but requires special tools and equipment. Fiberglass insulation in rolls or batts can be easily added by the homeowner.

Other Areas to Insulate

Insulate your attic, outer walls and crawl space first, as these areas are most susceptible to heat transfer.

  • Insulate water heaters to prevent costly energy loss. Look for insulating pre-cut jackets or blankets with an insulating value of at least R-8. Adding insulation to your water heater can reduce standby heat losses by 25 percent to 45 percent. This will save you around 4 percent to 9 percent in water heating costs.
  • Wrap hot water pipes with tubular insulation to prevent freezing and help keep water hot. Use quality pipe insulation wrap. Insulating your hot water pipes reduces heat loss and can raise water temperature by 2 to 4 degrees vs. non-insulated pipes, allowing you to use a lower temperature setting.
  • Insulated heating and air conditioning vent ducts operate more efficiently and vibrate less, reducing noise. Properly insulating air ducts located in unconditioned spaces such as attics, crawl spaces, garages or unfinished basements can help improve your home's energy efficiency.

Installation Tips

You can rent an insulation blower from The Home Depot to install insulation yourself, or hire a professional from our installation services.

  • Make sure that your house is properly ventilated. Adequate ventilation is necessary to prevent too much heat and condensation from building up.
  • Plug leaks to prevent air from getting in and out in areas around windows and doors. Always fix leaks before installing insulation, as they may be difficult to find after the job is finished.
  • Wear long sleeves and pants, work gloves, safety glasses, and a dust mask or respirator to avoid irritating your skin or breathing in harmful substances. Vacuum your clothing immediately after to help reduce the chances of skin irritation.