hwINSULATION CONTRACTORS ASSOCIATION OF AMERICA

Technical Bulletin1321 Duke Street, Suite 303 • Alexandria, VA 22314 • (703) 739-0356 • FAX (703) 739-0412

No. 21: Insulating Basements and Crawl Spaces (Revised 7/04)

In all cases, consult with the project architect, engineer, or building code official. ICAA Technical Bulletinsare provided for informational purposes only . ICAA and/or its members are not responsible for loss or damage

caused by errors or omissions or any other cause .

SCOPE: This bulletin describes various applicationtechniques for insulating walls and ceilings of basements andcrawl spaces .

INTRODUCTION : The International Energy ConservationCode establishes minimum energy efficiency standards forinsulating basements and crawl spaces . The choice of aparticular method or material will depend upon many factors,such as presence of water lines, HVAC ducting andmechanicals, type of floor support structure and subflooringmaterials, and other building code requirements . This bulletinprovides information about where and how various insulationmaterials should be used to insulate basements and crawlspaces to meet local building code requirements and avoidpotential problems. Consult with your local jurisdictionregarding codes in your area .

LIMITATIONS : This bulletin does not cover all possiblemethods and materials suitable for insulating basements andcrawl spaces. Recommendations from the materialmanufacturer should be solicited . However, it remains thefinal responsibility of the architect/engineer to ensure properdesign and application of the materials in question .

BASEMENTS : If the basement space is heated or isunconditioned but contains heating units, ducts and pipes, orother appliances, the walls should be insulated instead of thefloor/ceiling . If the basement space is unheated, it may beappropriate to insulate the floor/ceiling . As an alternative,insulation may be applied to the walls, and, in some cases, thismay be the only alternative . However, insulation shouldalways be applied to the band joist .

CRAWL SPACES : Crawl spaces may have cement or dirtfloors, provide combustion air to furnaces, and include pipesand ducts . Either the walls or the floor/ceiling should beinsulated, but not both . If the floor/ceiling is insulated, allpipes and ducts must be insulated as well . Regardless ofwhere insulation is placed, the entire floor area should becovered with a 4 mil or thicker plastic sheeting (ground cover)extending partially up the vertical wall to reduce moistureproblems . Check codes on how far the ground cover shouldextend up the vertical wall .

FLOOR/CEILING :

• If faced insulation is used, the facing must always bein substantial contact with the subflooring, unless thefacing has a Flame Spread Index (FSI) of 25 or less .

•

All types of unfaced insulation and faced insulationwith the facing rated FSI of 25 or less are notrequired to contact the subflooring, and may form anair space between the insulation and subflooring .

• All types of insulating materials must be securelyheld in place by means of support rods, wire mesh,netting, drive pins, or other mechanical means .

•

Currently, the International Residential Code requiresa vapor retarder on the warm-in-winter side ofinsulation ; however, some exceptions are granted .Consult with the material manufacturer and the localcode official . Plywood subflooring of 1/2 inchthickness or greater may be an approved vaporretarder . There are also approved vapor retarderpaints .

•

If an "encapsulated insulation" product is used, thevapor retarder should be installed on the warm-in-winter side of the insulation . Consult with thematerial manufacturer and the local code official forthe proper location of the vapor retarder .

•

Most codes require protection of foam plasticinsulation with an approved fire rated barrier unlessan exception been granted . Requirements differ forbasement and crawl space floor/ceilings . Consultwith the material manufacturer and local buildingcodes .

• All exposed insulation and facings must have a FSIof 25 or less . Refer to the local building code withjurisdiction .

WALLS:

When truss type or wood I-beam joists are present, itmay be more practical to insulate the walls of thefloor/ceiling .

•

Basement or crawl space walls are constructed ofmasonry or wood framing and may be subject tobelow grade water leakage from the exterior side .Because of this, particular attention should be givento protecting the insulation from becoming wet andsubject to deterioration and loss in R-value . It shouldbe determined whether the exterior of the wall hasbeen treated to reduce or eliminate water leakage .

•

It is a good practice to apply vapor retardant paint orattach an approved vapor retarder to the interior wallsurface from one foot above the outside ground levelto the floor before insulating . In crawl spaces withdirt floors, plastic film should cover the entirehorizontal surface of the ground and at least 6 inchesvertically up the walls . This practice will all buteliminate moisture related problems .

• Insulation should be continuous from the top of thewall to the floor of crawl spaces less than 12 inchesin height and should extend horizontally across thefloor of crawl spaces for a minimum of 12 inches .

•

Any rigid, flexible, or spray applied insulationmaterial may be used . Consult with the materialmanufacturer for proper application techniques. Theimportant criteria is that it remain in place .

•

Most codes require protection of foam plasticinsulation with an approved fire rated barrier unlessan exception has been granted . Requirements differfor basement and crawl space walls . Consult withthe material manufacturer and local building codes .

• All exposed insulation and facings must have a FSCof 25 or less . Refer to the local building code withjurisdiction. Note that there have been some caseswhere the foil facing of FSC of 25 or less insulationhas given electrical shocks to installers when a "hot"electrical wire is in contact with the facing .

•

Basement walls which will be enclosed with aninterior finish should be insulated in the same manneras exterior walls on floors above the basement .

•

Apply insulation to all band joist areas so that it issecurely in place. If faced insulation is used, thefacing should be in contact with the joist. Many codeofficials do not permit exposed facings .

When crawl space wall insulation techniques arechosen over floor/ceiling insulation, ventilation isunnecessary and not energy efficient according totoday's building scientists . Check building codes asthey are subject to change . Vents must be provided,but it is suggested they be closed and insulated if thewalls are insulated AND proper moisture controlmeasures have been taken .

In regions where termite infestation is common, localcode officials may require a continuous 6 inch high"inspection strip" around the perimeter at the top ofinsulated exterior basement and crawl space walls .This may also be required at the bottom of insulatedexterior walls where there is no finished floor (i .e .,soil, stone, etc .) . In some areas, use of foam plasticinsulation below grade on the external of foundationwalls is prohibited . Consult with your local buildingcode official .

There are many acceptable wall insulationtechniques . Some are identified in Figures A - F .For further information, contact the Energy &Environmental Building Association atwww.eeba.org .

BAND JOISTINSULATION (WITHVAPOR RETARDER)

GRAVEL

DRAIN TILE

VAPOR RETARDER(MIN 4 MIL .)

TB 21A

WOOD FRAMED INTERIOR BASEVE\TINSULATION I\STALLATION

SUBFLOOR

JOIST

WALLINSULATONWITH VAPORRETARDER

INTERIORCOVERING

CONCRETE

2/99

BAND JOISTINSULATION (WITH FSC 25VAPOR RETARDER)

SILL SEALER411, `

MASONRY WALL

-1111'=1111

WATERPROOFCOATING

IMPALING PIN WITHPROTECTIVE CAP

GRAVEL

DRAIN TILE

VAPOR RETARDER(MIN 4 MIL .)

TB 21B

\TTRIOR BOARD-TYPE 0\SUL_ATIO\ I\STAL_L_ATIO\

1

O

O

NOTES: O WHEN FLOOR IS UNFINISHED (IE . SOIL, STONE, ETC .),IN REGIONS OF HEAVY TERMITE INFESTATION, LOCALINSPECTORS MAY REQUIRE AN "INSULATION STRIP"AT BOTTOM OF THE INTERIOR FOUNDATION WALL .IF SO REQUIRED, INSTALL INSULATION 6" INCHESUP FROM TH BOTTOM OF THE WALL .

2OFOR BASEMENT OR CRAWL (GREATER THAN12" IN HEIGHT APPLICATIONS.)

SUBFLOOR

JOIST

INSULATIONWITH FSC25 FACING

APPROVEDTAPE(FULL HEIGHT)

2/99

BAND JOISTINSULATION (WITH FSC 25VAPOR RETARDER)

SILL SEALER

MASONRY WALL

WATERPROOFCOATING

2x4 WOODFRAMING

GRAVEL

DRAIN TILE

VAPOR RETARDER(MIN 4 MIL .)

TB 21C

\TERIOR BATT/BLA\KETINSULATION I\STALLATIO\ ©

'1i~III-

NOTES:O WHEN FLOOR IS UNFINISHED (IE . SOIL, STONE, ETC .),IN REGIONS OF HEAVY TERMITE INFESTATION, LOCALINSPECTORS MAY REQUIRE AN "INSULATION STRIP"AT BOTTOM OF THE INTERIOR FOUNDATION WALL .IF SO REQUIRED, INSTALL INSULATION 6" INCHESUP FROM TH BOTTOM OF THE WALL .

2©FOR BASEMENT OR CRAWL (GREATER THAN12" IN HEIGHT APPLICATIONS.)

SUBFLOOR

JOIST

INSULATONWITH FSC 25FACING

CONCRETE

FURRINGSTRIP

2/99

1\ TERIOR CRAWL SPACEINSLLATIO\ I\STALLATIO\ O

NOTES;O WHEN FLOOR IS UNFINISHED (IE. SOIL, STONE, ETC .),IN REGIONS OF HEAVY TERMITE INFESTATION, LOCALINSPECTORS MAY REQUIRE AN INSULATION STRIP"AT BOTTOM OF THE INTERIOR FOUNDATION WALL .IF SO REQUIRED, INSTALL INSULATION 6" INCHESUP FROM TH BOTTOM OF THE WALL .

2©FOR CRAWL SPACE APPLICATIONS LESS THAN12" IN HEIGHT

©SOME JURISDICTIONS MAY REQUIRE FSC 25 FACINGON EXPOSED CRAWL SPACE INSULATION .

TB 21D

2/99

INSULATION OWITHVAPOR RETARDER

INSULATIONWITH

LESS THAN 12"

VAPOR RETARDER

VAPOR RETARDER(MIN. 4 MIL .)COVERING GROUND

TB 21E

EXTERIOR CRAWL SPACE

I\SULATIO\ I\STALLATIO\

INSULATION WITHVAPOR RETARDER

BRICK OR GRAVELFOR HOLDDOWN

VAPOR RETARDER(MIN. 4 MIL)

NOTES:Ol IN REGIONS OF HEAVY TERMITE INFESTATION, LOCAL INSPECTORSMAY REQUIRE A "INSPECTIION STRIP" AT THE TOP OF THE EXTERIORFOUNDATION WALL, IF SO REQUIRED, INSTALL INSULATION 6 INCHESDOWN FROM THE TOP OF THE WALL .

OFOR CRAWL SPACE APPLICATIONS REGARDLESSOF HEIGHT

©SAME JURISDICTIONS MAY REQUIRE FSC 25 FACINGON EXPOSED CRAWL SPACE INSULATION .

2/99

FOOTERDRAININGCOARSEGRAVEL

TB 21F

1\

EXTERIOR BASEVE\T

S,LATIO\ I\STALLATIO\

SILL SEALER

WATER SHEDDINGTOPSOIL LAYER

RIGID INSULATION

WATERPROOFINGMEMBRANE

f--VAPORRETARDER(MIN, 4 MIL.)

NOTES: Q1 IN REGIONS OF HEAVY TERMITE INFESTATION, LOCAL INSPECTORSMAY REQUIRE A INSPECTIION STRIP" AT THE TOP OF THE EXTERIORFOUNDATION WALL. IF SO REQUIRED, INSTALL INSULATION 6 INCHESDOWN FROM THE TOP OF THE WALL .

2/99

S" MASONRY BLOCK

MOISTURE RETARDER

FOOTING

-XTERIOR I\SULATE3 WITISPRAY APPLI-3 POLYURET - A\

FOAV I\S.~LATIO\

SPRAYED POLYURETHANE0FOAM

1/2" GYPSUMWALLBOARDOR EQUIVALENT

FURRING STRIPS/STUDS

SPRAYED POLYURETHANE FOAM

POLYURETHANE INSULATION

VAPOR RETARDER(MIN. 4 MIL .)

NOTES : CD IN REGIONS OF HEAVY TERMITE INFESTATION, LOCAL INSPECTORSMAY REQUIRE A "INSPECTIION STRIP" AT THE TOP OF THE EXTERIORFOUNDATION WALL. IF SO REQUIRED, INSTALL INSULATION 6 INCHESDOWN FROM THE TOP OF THE WALL.

2©FOR CRAWL SPACE APPLICATIONS REGARDLESSOF HEIGHT

TB 21G

2/99

I\TERIOR INSULATED WITHSPRAY APPLIED POLYURETHA\E

FOA V I\SULATIO\ O

FINISH FLOOR

SUBFLOOR

FLOOR JOIST

SPRAYED POLYURETHANE FOAM

APPROVED FSC 25 FINISH

NOTES:O WHEN FLOOR IS UNFINISHED (IE . SOIL, STONE, ETC .),IN REGIONS OF HEAVY TERMITE INFESTATION, LOCALINSPECTORS MAY REQUIRE AN "INSULATION STRIP`AT BOTTOM OF THE INTERIOR FOUNDATION WALL .IF SO REQUIRED, INSTALL INSULATION 6" INCHESUP FROM TH BOTTOM OF THE WALL .

TB 21H

2/99

BAND JOISTINSULATION (WITHVAPOR RETARDER)

GRAVEL

DRAIN TILE

VAPOR RETARDER(MIN 4 MIL .)

BASEMENT CEILI\G INSULATIC\I\STALLATIO\

NOTES;OVAPOR RETARDER TO FACE WARM SIDE IN WINTER

TB 211

SUBFLOOR

CEILINGINSULATIONTIGHT TO FLOORABOVE. O

CONCRETE

2/99