BASC Search | Building America Solution Center

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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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.

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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.

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

Video

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

Building Code Training - Residential Thermal Envelope - Air Sealing

Presentation

Presentation describing the Georgia State Minimum Standard Energy Code air barrier requirements, envelope concepts including air flow and thermal properties, and common missed insulation and air-sealing opportunities.

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

Guide

Guide describing vapor retarder permeability, insulation interaction, and example construction in a hot-humid climate.

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

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

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Right – Workers pour the concrete for the basement floor slab over a vapor barrier installed over rigid foam.

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Polyethylene Over Aggregate

CAD File

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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Flow-Through Assemblies, BSI-091

Reference

Article discussing flow-through assemblies of walls.

Cement Board Installed behind Tile and Panel Tub and Shower Enclosures

Guide

Guide describing how to install moisture-resistant materials on walls behind showers and tubs to help manage moisture.

Stump the Building Chump – Joe Lstiburek

Presentation

Webinar answering code-related questions on insulating historic masonry buildings, mechanical ventilation, combustion equipment, excessive humidity build-up, skylights, and vapor retarders on interior walls.

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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2021 IBC and IRC Adopt Improved Vapor Retarder Requirements

Reference

Article describing vapor retarder requirements in the International Residential Code and International Building Code 2021.

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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Radon Fan

Guide

Guide describing how to install a radon mitigation fan to actively remove radon from the home.

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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Moisture Control for Residential Buildings

Reference

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

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.

Building Science Introduction - Moisture Flow

Information Guide

Information guide describing the concept of moisture flow in residential buildings.