Insulation Types, Materials & R Values for Basements, Crawl Spaces & Attics

Before insulating your basement, crawl space, attic or any other interior wall, you should have a basic understanding of the different types of insulation solutions available. Emily Patterson from Ehow contributed the following great piece:

Insulation and air sealing in the basement reduces energy use and lowers heating and cooling costs. Insulation’s R-value is the resistance to heat flow through the insulation. Higher R-values indicate a higher resistance to heat flow (and thus higher energy savings). According to the U.S. Department of Energy, insulating the basement of a home can save $250 to $390 a year, depending on the location and R-value of the insulation used.

Blanket Insulation

Blanket insulation, also called batt and roll insulation, is the most common insulation used in basements. The product can be made with fiberglass, natural fibers, mineral wool or plastic fibers. The rolls are protected with a variety of coverings. Some products have a heavy paper covering on only one side, some are available with a paper cover on both sides. Plastic, foil and fire-rated products are also available—local building codes may require the use of certain types of insulation for basement installation.

Foam Board Insulation

Foam board insulation is a newer product on the market. The foam boards are made from polyisocyanurate, polystyrene or polyurethane. The foam board is installed between studs or can be glued into position and the seams taped before the installation of studs or wall finishes. It is important to maintain moisture control with foam board insulation, as pores in the foam can absorb water and allow mold growth. Local ordinances often require a fire barrier between flammable foam board insulation and the interior of the house. Check your local building codes to find out the requirements for your town if you use foam board for basement insulation.

Loose Fill Insulation

Loose fill insulation is blown into cavities and is a good choice for basements that are already finished. The fill is made from fiberglass, rock wool or cellulose. Fiberglass is suitable for most finished basement applications. However, rock wool and cellulose should not be considered for areas where the studs are located 24 inches apart. Over time, loose fill insulation can settle, reducing the insulation’s R-value. Additional insulation can be added to fill voids when settling has occurred.

Sprayed Foam Insulation

Sprayed foam insulation is installed using a foaming agent combined with liquid foam insulation. This type of insulation requires certification to install properly. However, the R-value of spray foam insulation is often much higher than the more commonly used and less expensive blanket insulation. Special equipment is also required for proper installation. In most locations, building codes require another barrier, such as drywall, to cover all sprayed foam insulation. A vapor barrier may also be required. Check with your local building codes for all statutes regarding sprayed foam insulation in basements.


Air sealing is just as important as insulation for finished basements. Air movement in and out of the house around pipes, vents and electrical lines exchange air from outside to the inside, raising heating bills and reducing the savings of installing insulation. Use expanding foam spray to seal the space between all breaks in the walls between inside and outside the basement for a properly insulated and air-sealed basement. Insulate cold water pipes to reduce moisture caused by the pipes sweating in a properly insulated basement.


Control water issues such as leaks and seepage before installing insulation in the basement. Prevent future problems or correct existing problems by having the soil graded properly away from the house. The slope for effective drainage is at least 1 inch per 8 feet; increase the grade as much as possible. Keep gutters and down spouts clean so water can drain freely from the gutter system. Downspouts should direct rainwater at least 8 feet from the foundation.

What is R value?

R value insulation ratings are used to measure insulations ability to resist heat flow. The higher the R value, the more effective it is. House Insulation should be purchased based on its R value, not thickness or weight.

Facts About R value

Some quick facts about R value are:

There are different types of house insulation materials, each having a different R value.
Some of the best insulation materials are:

Table of R Value

Some quick facts about R value are:

R value for house insulation standards

table of r value for house
insulation standards

The house insulation r value of insulating boards are:

Expanded polystyrene 4.00 per inch
Extruded polystyrene 5.00 per inch
Polyisocyanurate &
6-7 per inch

In most regions of North America an R Value of 11 is sufficient in a basement. If it is a Crawl Space you will want an R Value of 19, and for attics you will want much higher, around 50. The house insulation r value of insulating boards are:

Type R/Inch
Blown Pink or Yellow Fiberglass 2.2
Blown White Fiberglass
(certainteed Insulsafe)
Blown Rockwool 2.8
Blown Cellulose 3.7
Batt Fiberglass 3.1
Batt Rockwool 3.2
Polystyrene (extruded) 5.0
Polystyrene (molded) 4.0
Polyurethane (unfaced) 6.0
Polyisocyanurate (unfaced) 6.0
Polyurethane (skin faced) 7.1
Polyisocyanurate (skin faced) 7.1
Loose Fill Vermiculite 2.4
Loose Fill Perlite 2.8