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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.

Moisture problems must be dealt with before sealing and insulating a crawlspace

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Right – Foundation drainage mat was installed over the waterproof membrane that covers the sealed crawlspace window

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Right – A sump pump with a perforated sump pit was installed in the crawlspace slab to reduce water accumulation under the slab

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Provide a continuous air barrier from the rigid foam below the crawlspace floor joists to the rim joist to the exterior wall above

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An exhaust fan pulls damp air out of a retrofitted sealed crawlspace while drawing in dry air from the living space

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Before sealing and insulating the crawlspace, the windows were sealed, the window wells backfilled, and sumps pumps were installed that discharged to the gutter downspouts

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Wrong – This vented crawlspace has standing water because steps were not taken to address site conditions that led to bulk water flow into the crawlspace

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Wrong – A poorly sealed window and window well allow bulk water to enter the crawlspace from ground that slopes toward the structure

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Water-proof materials cover the exterior side of crawlspace windows in a crawlspace retrofit, while foil-faced rigid foams seals and insulates the inside face of the openings

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Right – Foil-faced insulation was added after the crawlspace was dried and sealed by diverting water runoff, sealing off crawlspace windows and vents, and adding sump pumps and exhaust fan ventilation

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Closed-cell spray foam insulates the floor above a vented crawlspace; a protection board made of fiber cement is screwed in place under the floor joists to keep out pests

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Right – This crawlspace window was completely sealed off on the inside and outside with air barrier and water-proof materials and the window well was filled in to an above-grade height to prevent bulk water from entering the crawlspace

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Understanding Basements, BSD-103

Reference

Information sheet with methods for constructing or retrofitting basements to reduce moisture issues.

Comprehensive water management features include a capillary break (≥ 6-mil polyethylene sheeting) at all crawlspace floors

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Taping polyethylene sheeting at interior pier footings

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Drain or Sump Pump Installed in Basements or Crawlspaces

Guide

Guide describing installation of sump pumps in the basement or crawlspace of a home.

Comprehensive above-grade water management details for a crawlspace foundation include a capillary break over the crawlspace floor, slope the surface grade away, installing gutters that slope away, and capillary break under sill plate.

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Increase Seismic Resistance and Thermal Performance of Basement, Crawl Space, and Crawl Space with Cripple Wall Foundations

Guide

Guide describing different options for providing seismic and thermal resistance for homes with basement foundations, crawlspace foundations, or crawlspace foundations with a "cripple" wall.

Retrofit Existing Crawl Space Foundations with Cripple Walls to Increase Seismic Resistance and Thermal Performance

Guide

Guide describing different options for providing seismic and thermal resistance for homes with 'cripple' wall crawlspace foundations, which are known for their instability.

Flood-Resistant Crawlspace Foundations

Guide

Guide describing how to design or retrofit a crawlspace to reduce the risk of damage during a flood event.

Radon Fan

Guide

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

Vertical Radon Ventilation Pipe

Guide

Guide describing how to install a radon-mitigating vertical ventilation pipe in new and existing homes with various types of house foundations.

Exterior Insulation for Existing Foundation Walls

Guide

Guide describing how to insulate a new foundation wall or an existing foundation wall by adding rigid insulation to the exterior side.

Capillary Break at Crawlspace Floor - Polyethylene Sheeting under Concrete Slab

Guide

Guide describing how to install a capillary break to help manage moisture in foundations.

Water Management of Existing Crawlspace Floor

Guide

Guide providing information about treating bulk water drainage issues and moisture control measures in existing basements and crawl spaces.

Water Management of Existing Basement Floor

Guide

Guide describing how to retrofit an existing basement floor or slab to reduce moisture issues.

Spray Foam Interior Insulation for Existing Foundation Walls

Guide

Guide describing how to insulate an existing foundation wall by adding spray foam insulation to the interior side of the wall.

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.

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.