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Rigid Insulation Over Aggregate

CAD File

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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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.

High-Performance Slab-on-Grade Foundation Insulation Retrofits

Reference

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

Vented crawlspace foundation insulated at floor joist with rigid foam.

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

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

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

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

Guide

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.

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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.

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

Video

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

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

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Polyethylene Over Aggregate

CAD File

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.