BASC Search | Building America Solution Center

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

Image

Right – A termite inspection gap is left at the top of the rigid foam board basement wall insulation.

Image

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.

Image

Right - This poured concrete basement wall is insulated on the exterior and under the slab with rigid insulation; footing details include interior and exterior footing drain pipe.

Image

The rim band connecting the insulated precast concrete basement walls to the floor joists above is spray foamed to provide air-sealing and insulation in this hard-to-seal juncture.

Image

Right - Concrete masonry unit (CMU) basement wall showing exterior insulation and sill detail; above-grade wall has sheathing to the inside of the rigid foam.

Image

Right – Precast concrete basement walls come to the site with integrated insulation and steel-faced concrete studs.

Image

Right - Precast concrete basement walls come to the site with integrated rigid foam insulation and steel-faced concrete studs.

Image

This exterior insulated slab-on-grade monolithic grade beam foundation is protected from pests by termite shield at the sill plate, borate-treated framing, flashing at end of wall insulation, brick veneer over slab-edge insulation, and rock ground cover.

Image

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

Image

A dimpled plastic water barrier protects the insulated concrete form basement walls and carries any ground water down the walls to the footing drain to minimize the opportunity for water intrusion and frost heave.

Image

Wrong - This plastic-covered blanket insulation is not perforated, does not cover the entire basement wall, is not sealed at the edges, and is not installed over rigid foam.

Image

Right - The concrete masonry unit (CMU) basement wall has exterior insulation; the footing details include interior and exterior footing drain pipe.

Image

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.

Image

Exterior surface of below-grade walls finished as follows: For poured concrete, concrete masonry, and insulated concrete forms, finish with damp-proof coating

Image

Right - XPS rigid foam board is tightly installed against a concrete foundation wall and seams are sealed with tape prior to installing fibrous blanket insulation.

Image

Right - Foil-faced polyisocyanurate rigid foam board is tightly installed and sealed against a concrete foundation wall prior to installing fibrous blanket insulation.

Image

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.

Image

Spray foam insulation extends down the foundation wall to the slab, which has been retrofitted by cutting the slab to install drainage mat against the wall and a new perimeter footing drain, along with rigid foam plastic above the slab.

Image

Spray foam extends down the foundation wall to the slab, which has been retrofitted by adding dimple plastic drainage mat and rigid foam insulation.

Image

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

Image

Right – Two inches of rigid foam was installed on the ground before pouring the basement floor slab while precast, pre-insulated concrete panels comprise the basement walls.

Image

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.

Image

Basement Blanket Insulation

Guide

Guide describing Installing blanket fiberglass insulation on the interior walls of a conditioned, unfinished basement as an alternative to best practice solutions.

Unvented, Insulated Crawlspaces

Guide

Guide describing method for insulating an unvented crawlspace or conditioned basement with rigid foam on the interior side of the walls.

How to Insulate a Basement

Video

Video describing how to warm up a chilly concrete wall with This Old House general contractor Tom Silva.

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.

Spray foam on concrete foundation wall with framed interior wall

CAD File

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.

The daylight basement walls are made of concrete walls with integrated rigid foam and steel-faced concrete studs.

Image