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This concrete masonry unit (CMU) wall is insulated with rigid insulation on the exterior side of the concrete block

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This concrete masonry unit (CMU) wall is insulated with rigid insulation on the exterior side of the concrete block

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Right – The basement of this cold-climate home is insulated along interior walls with 2 inches of foil-faced rigid foam; finished basement walls also have a 2x4 interior wall insulated with R-19 blown-in fiberglass insulation and a poly vapor barrier.

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

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Walls in cold climates with a polyethylene vapor barrier interior of the wall cavity should have either no exterior insulation or a vapor-open continuous insulation like mineral wool that allows drying to the exterior

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The Perfect Wall includes water, air, thermal, and vapor layers with continuous insulation exterior of the sheathing to reduce the condensation potential in the wall.

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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

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

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Masonry wall interior retrofit with parge coat, fluid-applied water control layer, rigid mineral wool, wood-framed wall with cavity insulation, smart vapor barrier, and wood or metal service cavity

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Vapor-permeable mineral wool insulation is installed on the exterior side of the sill beam during an exterior wall retrofit to allow the sill beam to dry to the outside

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Walls in cold climates with a Class 3 vapor retarder (latex paint) and a vapor-open continuous insulation like mineral wool allow drying to the interior or the exterior

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Wrong - The fiberglass blanket insulation has no perforated vapor retarder, does not cover the entire basement wall, is not sealed at the edges, and is not installed over rigid foam.

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Right - This crawlspace, which is insulated on the floor, has a complete vapor barrier over the floor and up the walls that is sealed at all seams and termite inspection gap at the top of the vapor retarder.

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When rigid foam insulation is applied to the exterior side of the wall cavity under the cladding, with seams taped and an air gap provided, it acts as a vapor barrier, air barrier, and rain screen.

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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.

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Condensation Control for Walls in Cold Weather

Guide

Guide describing ways to construct wall assemblies in cold climates to minimize the likelihood of condensation formation inside the walls.

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

Guide

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

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

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

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Construction Guide - Next Generation High Performance Walls in Climate Zones 3-5, Part I: 2x6 Walls

Reference

Part I of the Guide addresses walls constructed with 2x6 wood frame studs, wood structural panel (WSP) sheathing as exterior sheathing, gypsum board as interior sheathing, and a cladding system installed over WSP sheathing in low-rise residential buildings up to three stories in height.

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.

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Rigid foam insulation can serve as the drainage plane when all seams are taped. Furring strips provide an air gap behind the cladding.

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The “institutional” perfect wall works in all climate zones; water, air, vapor, and thermal control layers are exterior of the sheathing, assembly allows drying to interior and exterior

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The Larsen-truss 9-inch wall cavities were covered with a smart vapor membrane that was fastened to the trusses with furring strips, which also provide an air gap behind the wood siding; each truss cavity is then filled with blown cellulose.

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This concrete masonry unit (CMU) wall is insulated with rigid insulation on the exterior side of the concrete block

This concrete masonry unit (CMU) wall is insulated with rigid insulation on the exterior side of the concrete block

Right – The basement of this cold-climate home is insulated along interior walls with 2 inches of foil-faced rigid foam; finished basement walls also have a 2x4 interior wall insulated with R-19 blown-in fiberglass insulation and a poly vapor barrier.

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

Walls in cold climates with a polyethylene vapor barrier interior of the wall cavity should have either no exterior insulation or a vapor-open continuous insulation like mineral wool that allows drying to the exterior

The Perfect Wall includes water, air, thermal, and vapor layers with continuous insulation exterior of the sheathing to reduce the condensation potential in the wall.

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

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

Masonry wall interior retrofit with parge coat, fluid-applied water control layer, rigid mineral wool, wood-framed wall with cavity insulation, smart vapor barrier, and wood or metal service cavity

Vapor-permeable mineral wool insulation is installed on the exterior side of the sill beam during an exterior wall retrofit to allow the sill beam to dry to the outside

Walls in cold climates with a Class 3 vapor retarder (latex paint) and a vapor-open continuous insulation like mineral wool allow drying to the interior or the exterior

Wrong - The fiberglass blanket insulation has no perforated vapor retarder, does not cover the entire basement wall, is not sealed at the edges, and is not installed over rigid foam.

Right - This crawlspace, which is insulated on the floor, has a complete vapor barrier over the floor and up the walls that is sealed at all seams and termite inspection gap at the top of the vapor retarder.

When rigid foam insulation is applied to the exterior side of the wall cavity under the cladding, with seams taped and an air gap provided, it acts as a vapor barrier, air barrier, and rain screen.

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.

Condensation Control for Walls in Cold Weather

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

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

Construction Guide - Next Generation High Performance Walls in Climate Zones 3-5, Part I: 2x6 Walls

Technology Solutions Case Study: Moisture Durability of Vapor Permeable Insulating Sheathing

Typical R-values and Vapor Retarder Classifications for Common Insulation Materials

Class I Vapor Retarders Not Installed in Above-Grade Walls in Warm-Humid Climate

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

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

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.

Rigid foam insulation can serve as the drainage plane when all seams are taped. Furring strips provide an air gap behind the cladding.

The “institutional” perfect wall works in all climate zones; water, air, vapor, and thermal control layers are exterior of the sheathing, assembly allows drying to interior and exterior

The Larsen-truss 9-inch wall cavities were covered with a smart vapor membrane that was fastened to the trusses with furring strips, which also provide an air gap behind the wood siding; each truss cavity is then filled with blown cellulose.