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Insulation Buying Guide

A man installing attic insulation.

Updated January 19, 2022

Brian G.

By Brian G.

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

Why Insulate?

Home insulation 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 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 air-conditioned spaces from spaces without air conditioning, such as the attic, crawlspaces and the garage. Fill all cracks or openings with insulation. To control heat leakage, apply caulk or foam sealants around openings, such as 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 that can damage your home and present a potential health concern. Insulation provides a barrier between vapor and the structure.

Conserve Water: Using pipe insulation can help reduce heat loss and raise the temperature of the water running through the pipes by 2 to 4 degrees. This means you can lower your water temperature setting and you won’t have to wait as long to get hot water from faucets or shower heads. Additionally, you’ll waste less water.


Insulation R-Value

A map showing the R-value recommendations for each US state.

Find where you live on the chart. Then match your area’s color to the corresponding R-value chart. R stands for resistance.

A chart showing the R-value recommendations for each U S region on the map.

Types of Insulation

The chart contains information on common types of insulation, as well as tips on where and how to use them. For more comfortable installation with less itch and dust, look for encapsulated roll insulation or batting wrapped in plastic.

A chart describing different types of insulation and giving tips on where and how to use them.

Where to Insulate

A man wearing a mask and blowing insulation into an attic.

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

Locating Under-Insulated Areas

Several key areas in homes are often uninsulated or under-insulated. This allows cold air or air from spaces without air conditioning to pass through, which means maintaining a comfortable temperature in living spaces requires more energy.

Check the following home areas:

  • Attic: Slide a yardstick or tape measure into the existing insulation. If it isn’t 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.
  • Crawlspace: Check between floor joists if vented, and check perimeter walls if unvented. The ground should be covered with a 6-millimeter 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 adjacent to spaces with air conditioning.
  • 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. Trapped moisture vapor may cause mold and mildew to grow. 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, you must place it on the side of the wall that’s warm in the winter. 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 isn’t recommended. In mixed climate areas, the vapor barrier is optional depending on the total design of a building. In cold climates, you almost always need a vapor barrier.

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

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