BASC Search | Building America Solution Center

Wrong – Don’t use nails to fasten poly vapor barrier around flex ducts; it will allow moist air to reach the ducts where it could condense and ruin the insulation.

Image

In warm-humid climates, do not install Class 1 vapor retarders on the interior side of air-permeable insulation in above-grade walls, except at shower and tub walls.

Image

Masonry wall interior retrofit with parge coat, fluid-applied water control layer, wood-framed wall with cavity insulation, smart vapor barrier, and wood or metal service cavity

Image

The builder laid down a 4-inch base of aggregate rock, then covered that with a plastic vapor barrier that is taped at all seams and around all penetrations before installing the rigid foam under-slab insulation.

Image

When rigid foam insulation is applied to the exterior side of the wall cavity under the cladding, with seams taped and an air gap provided, it acts as a vapor barrier, air barrier, and rain screen.

Image

Masonry wall interior retrofit with parge coat, fluid-applied water control layer, rigid mineral wool, wood-framed wall with cavity insulation, smart vapor barrier, and wood or metal service cavity

Image

The builder in this very cold climate installed three layers of unfaced mineral wool batt in the double wall with a code-required vapor barrier between the middle and inner layers of wall insulation that is taped to barriers in the ceiling and floor.

Image

Retrofit an existing roof by installing rigid foam above the roof deck with a ventilation space between the rigid foam and the new roof sheathing plus new moisture and air control layers and cavity insulation in the roof rafters.

Image

A paint-on waterproofing covers the exterior and tops of the concrete block foundation walls and piers to block moisture moving up through the concrete, while foil-faced R-13 insulation lines the inside surface of the exterior walls.

Image

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.

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

High moisture levels were detected in this crawlspace by visual inspection of sagging ceiling insulation and deteriorating floor joists (left), high wood moisture content measured with a pin sensor (center), and high humidity levels in the air (right).

Image

Vinyl Siding with Integrated Rigid Foam for Existing Walls

Guide

Guide describing the design and installation considerations for recladding of above grade walls using insulated vinyl siding.

Building Materials with High Moisture Content Not Enclosed

Guide

Guide describing why and how to avoid using damp materials in construction.

Condensation Control in Attics and Roofs in Cold Weather

Guide

Guide describing causes of condensation in attics and roof assemblies during cold weather and ways to reduce this condensation.

Condensation Control for Walls in Cold Weather

Guide

Guide describing ways to construct wall assemblies in cold climates to minimize the likelihood of condensation formation inside the walls.

Moisture Management in Residential Construction Series - Building Enclosure: Window Installation

Video

Video describing the installation of windows to be air- and water-tight, including recommendations on flashing, air-sealing, and insulation, from Home Innovation Research Labs

Moisture Management in Residential Construction Series - Building Enclosure: Exterior Wall Overview

Video

Video from Home Innovation Research Labs giving an overview of moisture problems common to exterior walls and how to mitigate these problems with proper framing, flashing, sheathing, cladding, and insulation.

They All Laughed, BSI-026

Reference

Article describing the evolution of the IRC to permit class 3 vapor retarders (latex paint) in walls coupled with exterior continuous insulation to allow drying and reduce condensation risk.

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.

Home Performance Assessment

Information Guide

Information guide describing how to apply a whole-house approach to home improvement with energy efficiency upgrades, improved indoor air quality, and increased comfort.

Air Sealing Drywall to Top Plate

Guide

Guide describing ways to seal drywall to the top plate of an exterior wall to air-seal the wall cavity.

Mastic Home Exteriors Installation Guide

Reference

Siding installation guide for Ply Gem Siding Group products.

Air Sealing Bathroom and Kitchen Exhaust Fans

Guide

Guide describing how to air-seal bathroom and kitchen exhaust fans.

Pre-Retrofit Assessment of Attics, Ceilings, and Roofs

Information Guide

Information guide describing things to consider in the attic, ceiling, or roof before attempting retrofits of items including HVAC, wiring, or structural systems.