Home Insulation Basics

Not quite sure where to start? Start with some of the basic questions below to help you figure out the differences between certain insulation types and learn how to pick out the right insulation for your project.

Johns Manville makes a variety of insulation types for every part of your home:

  • Formaldehyde-Free™ Fiberglass Batts and Rolls: available in different thicknesses, R-values and widths to accommodate standard-size walls, crawl spaces, attics and more. Additionally, our different product offerings help make installation easier. Fiberglass insulation is available in many different forms, including rolls and pre-cut batts to fit all standard and non-standard wall cavities. Fiberglass comes in a variety of R-values for different applications throughout your home. Before you begin an insulation project, you should verify the size of your wall cavities (generally 16” or 24”) and attic space to calculate how much insulation you will need. Check out our Project Guide to determine what type of fiber-glass insulation is required for your project.
  • Blow-in Loose FiberGlass: Typically used in unfinished attics, nonconforming spaces and hard-to-reach areas such as corners, edges and around framing. Requires a blowing machine for installation.
  • Spray Foam: This alternative to fiberglass is most commonly used in new construction. It is applied using a specific spray applicator―resulting in a thermal, air and moisture barrier. JM provides a variety of closed-cell and open-cell spray foam solutions to meet specific building and climate needs.
  • Mineral Wool: Specifically designed to deliver robust sound dampening, exceptional fire resistance and superior temperature control, it is most commonly installed in wood-stud cavities of interior and exterior walls, basements, ceilings, floors and crawl spaces.
  • Foam Sheathing: Rigid-foam-sheathing insulation for use in commercial and residential construction where continuous insulation and/or high thermal efficiency is required. JM provides sheathing solutions for both interior and exterior applications.

What is R-value?

R stands for resistance to heat flow. The higher the R-value, the greater the insulating power and resistance to heat flow. Depending on where you live and what area of your home you are insulating, different R-values are recommended. For example, a colder climate requires higher R-values than a milder, more temperate one. R-values may be added together for increased thermal resistance.

What R-Value Do I Need?

Depending on where you live and the part of your home you’re insulating (walls, crawl space, attic, etc.), you’ll need a different R-value. Typical recommendations for exterior walls are R-13 to R-23, while R-30, R-38 and R-49 are common for ceilings and attic spaces. See the Department of Energy’s (DOE) ranges for recommended levels of insulation below.

Area of Home Good Better Best
Attics R-30 R-38 R-49
Cathedral Ceilings R-19 R-30 R-38
2×4 Walls R-13 R-15
2×6 Walls R-19 R-21
Floors R-19 R-25 R-30
Crawl Spaces R-19 R-25 R-30
Basement Walls R-11 R-13 R-15

Where Should I Insulate?

Ideally, you should insulate your entire home — from the attic to the crawl space and everything in between. Proper insulation and air sealing can dramatically improve the energy efficiency and comfort of your home. Common insulation projects include attics, crawl spaces, exterior and interior walls, basements and ceilings.

How Much Insulation Do I Need?

The amount of insulation needed depends on the type of insulation you’re using, the R-value you want to achieve, and the size of the space you’re insulating. Use our Project Guide to help you calculate how much insulation you need for each project.

How Can I Reduce The Moisture In My Home?

Using insulation with a vapor retarder or adding one to existing insulation helps keep the moisture inside your home from escaping and condensing in insulated cavities, which can cause mold and mildew. Check your local building codes for vapor retarder requirements.