Lowe's Home Improvement
FREE PARCEL SHIPPING on Qualifying Orders

Insulation Buying Guide

Johns Manville insulation

Insulation is what helps keep your home warm in the winter and cool in the summer. It also gives your heating and air conditioning units a break during these months. However, knowing what kind of insulation you need, where you need it, and what an R-value is can be confusing. Read on to help you find the type of insulation that fits your needs.

Why Insulate?

Lower energy bills - Insulation keeps your home warmer in the winter, which lowers your heating costs. In the summer, insulation keeps your home cooler, which eases the load on your air conditioner.

Control sound - Insulation can actually absorb sound, reducing the unwanted noise from appliances, audio equipment, conversation and other sources of sound that are transmitted through your walls and floors. The easiest way to make your home quieter is to use sound-control insulation in the interior walls. Even if you only insulate key rooms, you'll notice the difference.

Increase energy efficiency - To increase the energy efficiency of your home, you should insulate all exterior walls that separate conditioned spaces from unconditioned spaces. Unconditioned spaces such as the attic, crawlspaces and the garage are outside the thermal envelope. Insulating these areas closes the thermal envelope from above. To make a more "secure" envelope, 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 the envelope.

Control moisture - Everyday activities such as cooking, washing and bathing add moisture to the air in your home in the form of 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.

Types of Insulation

Chart with types of insulation

Where to Insulate

Woman installing attic insulation

Checking your current attic insulation depth is a good first step. You need up to 19 inches (or R-49). If you don't have enough, it may be an indication that your home is underinsulated and may not be properly sealed. Adding insulation to underinsulated areas and sealing air leaks are the fastest, easiest ways to help you lower your energy bill.
Locating Underinsulated Areas
There are several key areas that are often uninsulated or underinsulated. These areas allow cold or unconditioned air to pass through, maintaining a comfortable temperature requires more energy, creating higher bills.
Check these areas for the opportunity to add insulation:

  • Attic - Slide a yardstick or tape measure into the existing insulation. If it is not up to 19 inches deep, add more.
  • Basement - check rim joists and basement walls.
  • Crawlspaces - 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 first, then check by removing an electrical outlet cover. 
  • Garage - check garage walls and ceilings that are adjacent to conditioned spaces in the house.
  • Knee walls - check behind kneewalls, which are walls between living spaces and the garage or attic.

How to Avoid the Chimney Effect
In cold weather, warm air is continually rising. Leaks into the attic allow the expensive, heated air to escape into the attic, while at the same time drawing in cold air to displace it from the basement or other exterior leaks. This continuous air movement makes the home feel drafty and raises energy bills. By sealing attic air leaks, you plug the escape route of rising air and effectively stop the chimney effect.
Check around your attic for these common sources of attic air leaks:

  • 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

Insulation R-Value

r-value map

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 region on the map and use the chart to determine the r-value you need.

Find Your R-Value





























You May Also Need

Vapor Retarder

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 retarders keep the moisture in the air in your house from condensing in the insulated cavities.

Whether your vapor retarder 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 retarder between the interior of your home and the insulation. If you live in a hot, humid climate, place the vapor retarder 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 retarder is not recommended. In mixed climate areas, the vapor retarder is optional depending on the total design of a building. In cold climates, a vapor retarder is almost always needed.

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