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Insulating a crawlspace foundation with “cripple wall” in warm climates; in Climate Zones 5+ replace the foil- or plastic-faced fiberglass batt/roll insulation with impermeable rigid insulation or closed-cell spray polyurethane foam

No Vapor Retarders on Interior Side of Air-Permeable Foundation Insulation

Vapor retarder plastic should not be installed over fibrous insulation on basement or crawlspace walls unless rigid foam or spray foam is installed directly against the concrete, behind the blanket insulation.

High-Performance Slab-on-Grade Foundation Insulation Retrofits

Author(s)

Goldberg Louise F,

Mosiman Garrett

Organization(s)

NorthernSTAR,

NSTAR,

University of Minnesota,

UMN

Publication Date

September, 2015

Report assessing slab-on-grade foundation insulation energy savings.

Vented crawlspace foundation insulated at floor joist with rigid foam.

Publication Date

Mon, 03/01/2021 - 12:00

The below-grade wall assembly includes dampproofing, draining details, and insulation.

Publication Date

Tue, 05/01/2012 - 12:00

Right – Prepoured foundation panels with integrated insulation and vapor barrier are installed in place.

Publication Date

Mon, 09/30/2019 - 12:00

Right - This rigid insulation is correctly installed in a level layer over aggregate; the seams will be taped

Capillary Break Beneath Slab - Polyethylene Sheeting or Rigid Insulation over Aggregate or Sand and Geotextile Mat

Guide describing how to install a capillary break under a slab foundation using either polyethylene sheeting or rigid insulation installed over aggregate or over sand and geotextile matting.

This house design in the Hot-Humid climate uses a slab foundation, masonry walls, and an Exterior Insulation Finish System (EIFS) cladding.

Publication Date

Thu, 09/01/2011 - 12:00

The floor of the sealed insulated crawlspace is covered with a heavy plastic vapor-barrier sheathing that is taped at all seams and around the foundation piers to prevent water vapor from moving into the crawlspace.

Publication Date

Thu, 08/17/2023 - 12:00

Right – The raised slab foundation has a 3-ft stem wall of filled concrete block, then is back-filled with compacted dirt and crushed rock, then insulated with 1” rigid foam covered with taped vapor barrier, under a floor slab.

Publication Date

Mon, 09/30/2019 - 12:00

This Texas homes uses a slab foundation including a 4-in.-thick post-tensioned monolithic slab with turned-down edges poured over a 6-mil polyethylene vapor barrier and capillary break; slab edge insulation is not used due to termite risk.

Publication Date

Thu, 09/01/2011 - 12:00

Water Managed Existing Sill Beams and Sill Plates

Guide describing how to insulate the sill beam or sill plate on the exterior side in a way that allows drying to the exterior, as part of an exterior wall upgrade.

Passive House Underslab Foam & Vapor Barrier: Karuna Video #6

Publication Date

February, 2012

Video describing the under slab and vapor barrier used on a passive house.

Wrong - Polyethylene sheeting should be lapped up sides of walls and pillars and taped

This exterior wall retrofit permits drying to the exterior of a sill plate installed on an untreated irregular foundation wall

Publication Date

Mon, 07/01/2013 - 12:00

This exterior wall retrofit permits drying to the exterior of a sill plate installed on an untreated flat foundation wall

Publication Date

Mon, 07/01/2013 - 12:00

Radon Fan

Guide describing how to install a radon mitigation fan with various types of house foundations.

Wrong - Class I vapor retarder over framed basement walls can cause condensation, mold, and rotting because plastic prevents drying to the inside; the outside should have waterproofing and vertical drainage, and the framing should be spaced from the wall.

Publication Date

Thu, 03/01/2012 - 12:00

Moisture Control for Residential Buildings

Author(s)

Lstiburek Joseph W

Organization(s)

Building Science Corporation,

BSC,

U.S. Department of Energy,

DOE

Publication Date

September, 2020

Report providing extensive guidance on controlling moisture in building envelopes through proper selection and installation on air, water, thermal, and vapor barriers.

Rigid Insulation Over Aggregate

Insulating a crawlspace foundation with “cripple wall” in warm climates; in Climate Zones 5+ replace the foil- or plastic-faced fiberglass batt/roll insulation with impermeable rigid insulation or closed-cell spray polyurethane foam

No Vapor Retarders on Interior Side of Air-Permeable Foundation Insulation

High-Performance Slab-on-Grade Foundation Insulation Retrofits

Vented crawlspace foundation insulated at floor joist with rigid foam.

The below-grade wall assembly includes dampproofing, draining details, and insulation.

Right – Prepoured foundation panels with integrated insulation and vapor barrier are installed in place.

Right - This rigid insulation is correctly installed in a level layer over aggregate; the seams will be taped

Capillary Break Beneath Slab - Polyethylene Sheeting or Rigid Insulation over Aggregate or Sand and Geotextile Mat

This house design in the Hot-Humid climate uses a slab foundation, masonry walls, and an Exterior Insulation Finish System (EIFS) cladding.

The floor of the sealed insulated crawlspace is covered with a heavy plastic vapor-barrier sheathing that is taped at all seams and around the foundation piers to prevent water vapor from moving into the crawlspace.

Right – The raised slab foundation has a 3-ft stem wall of filled concrete block, then is back-filled with compacted dirt and crushed rock, then insulated with 1” rigid foam covered with taped vapor barrier, under a floor slab.

This Texas homes uses a slab foundation including a 4-in.-thick post-tensioned monolithic slab with turned-down edges poured over a 6-mil polyethylene vapor barrier and capillary break; slab edge insulation is not used due to termite risk.

Water Managed Existing Sill Beams and Sill Plates

Passive House Underslab Foam & Vapor Barrier: Karuna Video #6

Wrong - Polyethylene sheeting should be lapped up sides of walls and pillars and taped

Right-Polyethylene sheeting is correctly installed over aggregate and taped to pillars and foundation wall

Polyethylene Over Aggregate

This exterior wall retrofit permits drying to the exterior of a sill plate installed on an untreated irregular foundation wall

This exterior wall retrofit permits drying to the exterior of a sill plate installed on an untreated flat foundation wall

Radon Fan

Wrong - Class I vapor retarder over framed basement walls can cause condensation, mold, and rotting because plastic prevents drying to the inside; the outside should have waterproofing and vertical drainage, and the framing should be spaced from the wall.

Moisture Control for Residential Buildings