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Insulation Buying Guide

Learn what kind of insulation you need, how much you need and where you need it to make your home more comfortable.

Man Installing Insulation in a Crawlspace.

Why Insulate?

Insulating your home provides several benefits beyond comfort. A properly insulated home provides:

Lower energy bills - Insulation keeps your home warmer in the winter and cooler in the summer, which lowers heating and cooling costs.

Sound control - Insulation absorbs sound, reducing the unwanted noise from appliances, audio equipment, conversation and other sources transmitted through your walls and floors. Make your home quieter with sound-control insulation in the interior walls. Even if you only insulate key rooms, you'll notice a difference.

Increased energy efficiency - To increase the energy efficiency of your home, insulate all exterior walls and floors that separate conditioned spaces from unconditioned spaces, such as the attic, crawl spaces and the garage. Fill all cracks or openings with insulation. To control heat leakage, apply caulk or foam sealants around openings like window and door frames and any openings where wires or pipes go through.

Moisture control - Everyday activities such as cooking, washing and bathing add moisture to the air in your home in the form of water vapor. This vapor can become trapped inside walls, resulting in mold and mildew growth, which can damage your home and present a potential health concern. Insulation provides a barrier between vapor and structure.

Insulation R-Value

R-value is the measure of a material's ability to resist heat conduction. The greater the material's R-value, the better it performs as an insulator. All values assigned to insulation are based on specific thicknesses and are usually noted on the packaging. Compressing or otherwise reducing the thickness of insulation reduces its ability to resist conduction.

Find Your R-value

Step 1

R-values zone map of US.

Locate your zone on the R-values map.

Step 2

Find your area's color on the corresponding R-values chart.

Zone Attic 2x4 Walls 2x6 Walls Floors Crawlspaces
7 R49 to R60 R13 to R15 R19 to R21 R25 to R30 R25 to R30
6 R49 to R60 R13 to R15 R19 to R21 R25 to R30 R25 to R30
5 R49 to R60 R13 to R15 R19 to R21 R25 to R30 R25 to R30
4 R38 to R60 R13 to R15 R19 to R21 R25 to R30 R25 to R30
3 R30 to R60 R13 to R15 R19 to R21 R25 R19 to R25
2 R30 to R60 R13 to R15 R19 to R21 R13 R13 to R19
1 R30 to R49 R13 to R15 R19 to R21 R13 R13

Types of Insulation

The chart contains information on common types of insulation, as well as tips on where and how to use them.

 

Type
What Is It?   Where Does It Go?   Why Do You Need It?   DIY Tips

Roll

Glass fibers in wide, puffy sheets with or without a paper or aluminum face.

Best for long, unobstructed spaces like over attic joists.

Stops heat loss into your attic. Wall insulation keeps out cold.

Must be measured and cut to fit walls or flat surfaces.

Batting

Glass fibers in puffy strips with or without a paper or aluminum face.

Attics, walls and between crawl space joists.

Stop heat loss into your attic. Wall insulations keeps out cold.

Don’t compress or flatten the batting. It reduces the R-value.

Blown-In

Loose cellulose or fiberglass that’s blown into attics.

Attics and some walls where there’s no existing insulation.

Loose insulation fills in around odd shapes and cavities.

Ask a Lowe’s associate about blowers to rent or borrow a unit. 

Spray Foam

Expanding foam enlarges as it cures; other types cure in the shape they’re sprayed.

Where pipes or wires enter a house and around windows where batting can’t reach.

Plugs hard-to-fill gaps.

Non-expanding foam around windows and doors prevents bowing the frames.

Rigid Foam

Sheets of extruded or expanded polystyrene.

Tuck between joists above the basement or crawlspace.

Foam boards insulate while providing a partial vapor barrier.

Seal rigid foam panels between foundation joists using spray foam.

Specialty

Pipe insulation, duct insulation and water heater jackets.

Around objects that store or distribute hot water and indoor air.

Keeps water hot; insulates ducts that pass through cold attics.

Insulate pipes wherever condensation is a problem.

Good to Know

For more comfortable installation with less itch and dust, look for encapsulated roll insulation or batting wrapped in plastic.

Where to Insulate

Woman Installing Roll Insulation in an Attic.

The easiest place to get a gauge on your home's current insulation condition is in the attic. You need up to 19 inches (or R-49) for efficiency. If you don't have enough, it may be an indication that your home is under-insulated and may not be properly sealed. Adding insulation to under-insulated areas and sealing air leaks may help lower energy costs.

 

Locating Under-Insulated Areas

There are several key areas that are often uninsulated or under-insulated. These areas allow cold or unconditioned air to pass through, which means maintaining a comfortable temperature requires more energy.

 Check the following home areas:

  • Attic: Slide a yardstick or tape measure into the existing insulation. If it is not at least 19 inches deep, add more.
  • Basement: Check rim joists and unfinished basement walls and compare depth with an R-value map and chart for your area.
  • Crawl space: Check between floor joists if vented, and check perimeter walls if unvented. Ground should be covered with a 6 mil polyethylene sheet.
  • Exterior walls and floors: Turn off the electricity, then remove an electrical outlet cover for a view of exterior insulation.
  • Garage: Check garage walls and ceilings that are adjacent to conditioned spaces.
  • Knee walls: Check behind knee walls, which are walls between living spaces and the garage or attic.

 

The Chimney Effect

In cold weather, warm air is continually rising. Leaks into the attic allow heated air to escape into the attic while drawing in cold air from the basement or through exterior leaks. This continuous air movement creates a draft and raises energy bills. Seal attic air leaks to plug the escape of rising air and stop the chimney effect.

Check around your attic for these common air leak sources:

  • Between floor joists behind knee walls
  • Attic hatch
  • Wiring holes
  • Plumbing vents
  • Open soffit (the box that hides recessed lights and the finished space above cabinets)
  • Recessed lights
  • Furnace flue

Vapor Barrier

Moisture in the air in the form of vapor is transferred along with heat. This is especially common in humid environments and in certain areas inside a home, such as bathrooms, kitchens and laundry rooms. When moisture vapor becomes trapped, mold and mildew growth can result. Vapor barriers keep the air moisture in your house from condensing in the insulated cavities.

Whether your vapor barrier is a facing or a film, it must be placed on the warm-in-winter side of the wall. If you live in a cold climate, place the vapor barrier between the interior of your home and the insulation. If you live in a hot, humid climate, place the vapor barrier toward the outside of the wall cavity.

Check local building codes and your climate for vapor retarder requirements. Generally, in hot, humid areas, using a vapor barrier is not recommended. In mixed climate areas, the vapor barrier is optional depending on the total design of a building. In cold climates, a vapor barrier is almost always needed.

The facing on faced insulation acts as a vapor retarder. If you need a vapor barrier and your insulation is unfaced, you must cover it with a polyethylene film.