BASC Search | Building America Solution Center

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

Image

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

Image

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

Image

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

Image

Measure Guideline: Hybrid Foundation Insulation Retrofits

Reference

Document providing information on basement insulation, air sealing and water management retrofits.

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

Image

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

Image

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

Image

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

Image

Basement Insulation, Info 511

Reference

Information sheet describing techniques for insulating basements.

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

Image

Complete water management strategy for a below-grade wall

Image

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

Image

The existing slab is retrofitted with epoxy paint, rigid foam insulation, sleepers (furring strips), and subfloor.

Image

Concrete Floor Problems, BSI-003

Reference

Information guide describing issues with concrete floors, in multiple climate zones.

An uninsulated (or existing insulated) basement slab is retrofitted to reduce moisture transmission by sealing with epoxy paint.

Image

Right - The existing basement slab is retrofitted by installing a dimple plastic drainage mat, rigid foam insulation, and a floating subfloor.

Image

The existing slab is retrofitted by coating with epoxy paint, then installing rigid foam insulation and a floating subfloor.

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

Rigid insulation and water control layers are installed on the exterior of a flat foundation wall; spray foam insulates the rim joist

Image

Drain or Sump Pump Installed in Basements or Crawlspaces

Guide

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

Spray foam extends down the inside of the foundation wall to the uninsulated slab; because the wall lacked exterior perimeter drainage, the slab was cut and an interior footing drain was installed.

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

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.

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.

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.

Flooding Overview

Information Guide

Overview guide describing residential floodproofing steps.

Rigid Foam Insulation Installed over Existing Foundation Slabs

Guide

Guide describing how to insulate an existing slab floor by adding rigid foam insulation over the slab then installing a floating subfloor.