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Foundation wall exterior board insulation with above-grade wall insulation

CAD File

Air Sealed, Insulated Basements

Guide

Guide describing how to insulate a basement to improve the overall thermal performance of the building and provide more dry, usable conditioned space for home occupants and HVAC equipment.

Moisture can migrate from below the foundation to the basement wall and insulation cavity in a conventional blanket insulation installation

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Right - Section view showing how to air-seal and insulate a basement wall with perforated blanket insulation by installing it over air-sealed rigid insulation board to reduce condensation risk in the fiberglass blanket.

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Wrong - Moisture from within the basement foundation wall can migrate into the insulation cavity in a conventional blanket insulation installation.

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Right - A continuous layer of rigid foam insulation is installed against the foundation, and the perforated fiberglass insulation blanket is installed over that and covered with a semipermeable facing.

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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.

Exterior XPS basement insulation is correctly installed to completely cover the foundation wall

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Right - This concrete basement wall has exterior rigid insulation and comprehensive moisture management details.

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Because the above-grade potions of the wall lack exterior insulation, condensation and even ice form during cold winter conditions

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Wrong - Air leakage from the conditioned space to the basement foundation wall can lead to condensation or moisture issues in a conventional blanket insulation installation.

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Foil-faced rigid foam and spray foam can be used to insulate a basement on the interior; use good moisture management techniques to keep the basement dry

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Exterior fiberglass insulation on this new home was (incorrectly) cut to terminate below-grade after backfill, which will expose the above-grade portions of the foundation wall to cold temperatures

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Right - Reduce condensation risks to blanket insulation by installing perforated vapor retarder covered fiberglass blankets over rigid foam that is air-sealed at all edges; staple the blanket to nailers and top/bottom plates and tape over the seams.

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Wrong - Plastic-covered blanket insulation that is installed directly against concrete walls with no rigid foam or closed-cell spray foam covering the concrete could trap moisture coming through the concrete, leading to mold, moisture, and odor problems.

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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.

Pre-Retrofit Assessment of Crawlspaces and Basements

Information Guide

Information guide describing things to consider when considering home retrofits in the basement or crawlspace including HVAC, wiring, or structural systems.

The goal of foundation moisture management is to construct the basement, crawlspace, or slab in a way that keeps moisture from getting in in the first place

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