Insulating Your Floors
Do the floors in your home feel cold? This probably means there is no insulation between you and your unheated basement or crawlspace. Fortunately, Owens Corning insulation products and our floor insulation guide make it easy to insulate your floors.
What’s your R-value?
Below are the U.S. Department of Energy recommended minimum R-values for your climate zone.
Your Climate Zone: 4
|Attics||2x4 Walls||2x6 Walls||Floors||Crawlspaces|
|Zone||4||R38 to R60||R13 to R15||R19 to R21||R25 to R30||R25 to R30|
Choosing the Right Insulation
Fiberglass insulation is sold in roll and batt form; both are available with or without kraft paper facing. Use the guide below to select the best insulation for your project.
Continuous rolls are easy to transport and can be cut to length; great for large areas.
Batts come in pre-cut lengths for faster installation and each package contains more square feet than rolls; ideal for framed cavities.
Faced insulation uses kraft paper vapor barriers to control moisture transmission between walls and floors.
Unfaced insulation does not have a vapor barrier; can be used over existing insulation in the attic, or where moisture control is not needed.
To calculate how much you need:
- Measure the length of the floor joists you want to insulate. Remember to measure the width between the floor joists so you select the correct insulation width.
- Divide floor area by the square foot coverage number on each package to determine how many packages you need.
Calculate Your Square Footage
The following products are recommended for use in floors. Add items to your list, and you’ll be able to view, print or email your checklist when you’re done.
- Install the insulation so that it maintains continuous contact with the subfloor above. Any gaps between the floor and the insulation can allow air movement that reduces the insulation R-value. Make sure the insulation expands to its full label thickness (any areas of compression will also cause a reduction of R-value).
- The insulation should be installed all the way back at the end of each joist run so that it touches the band joist. You want complete coverage under the house. There will usually be a narrow joist space on the walls that run parallel to the joist. The insulation should be cut to fit this space.
- There are often both pipes and wires in crawl spaces under floors, and occasionally there will be a junction box. You may need to cut or split the insulation to fit it around electrical wiring, boxes and drain pipes.
- Likewise, the insulation will have to be cut or split so that it fits around cross braces. Do not leave voids (uninsulated areas) or overly compress the insulation.
- To support the insulation, use nylon banding or metal insulation supports. Wood furring strips can also be used.
- Install a 4- to 6-mil polyethylene ground cover to keep ground moisture from rising up into the space. All joints / seams in the poly should be overlapped a minimum of 6" and sealed. The ground cover should run up the crawl space wall, on all sides, a minimum of 6" and be sealed to the wall.
NOTE: Do not leave faced insulation exposed. The facings on kraft-faced insulation will burn and must be installed in substantial contact with an approved interior finish as soon as the insulation has been installed. Facing must be installed in substantial contact with an approved ceiling, floor or wall material. Keep open flame and other heat sources away from facing. See package for warnings, fire hazard and instructions, or call 1-800-GET-PINK®. Check your local building codes for requirements in your area.
- Tape measure
- Utility knife
- Straightedge or 2 x 4 (for cutting insulation)
- Lightweight, squeeze-type stapler
- Work gloves
- Loose-fitting, long-sleeved shirt
- OSHA-approved safety glasses
- Disposable dust mask
- Portable work light
Before you begin any insulation project make sure you:
- Seal any open penetrations
- Gather the necessary tools and wear protective gear listed above
- Always use a portable work light to ensure you have enough light in your work environment
- Leave EcoTouch® PINK® insulation in its wrapper until you are ready to use it
- Packaged insulation is highly compressed and expands greatly when the wrapper is opened
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