Question? Just ask us!
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
InspectAPedia ® Home
EXTERIORS of buildings
ADHESIVES, EXTERIOR CONSTRUCTION
AGE of a BUILDING - how to determine
AIR LEAK DETECTION TOOLS
AIR LEAK MINIMIZATION
AIR LEAK SEALING PROCEDURE
AIR SEALING STRATEGIES
ALGAE, FUNGUS, LICHENS, MOSS
ARCHITECTURE & BUILDING COMPONENT ID
ATTIC CONDENSATION CAUSE & CURE
BEST CONSTRUCTION PRACTICES GUIDE
BRICK VENEER WALL LOOSE, BULGED
BRICK WALL DRAINAGE WEEP HOLES
BOOKSTORE - EXTERIORS
CHIMNEY INSPECTION DIAGNOSIS REPAIR
DECK & PORCH CONSTRUCTION
DECK COLLAPSE Case Study
DECK FINISHES COATINGS PRESERVATIVES
DECK FLASHING LEAKS, ROT Case Study
CONDENSATION or SWEATING PIPES, TANKS
COOLING LOAD REDUCTION by ROOF VENTS
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
EARTHQUAKE DAMAGED FOUNDATIONS
EIFS & STUCCO EXTERIORS
ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY
EXTERIOR WALL SIDING TRIM & FINISHES
FIBERGLASS INSULATION MOLD
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FOOTING & FOUNDATION DRAINS
FOUNDATION CRACKS & DAMAGE GUIDE
HEAT TAPES & CABLES for ROOF ICE DAMS
HOUSEWRAP AIR & VAPOR BARRIERS
ROOF ICE DAM LEAKS
INSECT INFESTATION / DAMAGE
INSULATION IDENTIFICATION GUIDE
INSULATION INSPECTION & IMPROVEMENT
LEAD POISONING HAZARDS GUIDE
LEAD PAINT REMOVAL ALTERNATIVES
LEAD PAINT REMOVAL TROUBLES
LEAD PIPES in BUILDINGS
LEAD in ROOFING, EFFECTS
LEAD TEST KIT for HOME USE
LEED GREEN BUILDING CERTIFICATION
LOG HOME GUIDE
MOISTURE CONTROL in BUILDINGS
MOLD DETECTION & INSPECTION GUIDE
MVOCs & MOLDY MUSTY ODORS
ODORS GASES SMELLS, DIAGNOSIS & CURE
PAINT & STAIN GUIDE, EXTERIOR
PAINT FALURE, DIAGNOSIS, CURE, PREVENTION
PAINT FAILURE DICTIONARY
PAINT SURFACE PREPARATION
PORCHES & Sunrooms
PORCH CONSTRUCTION & SCREENING
SHEATHING, GYPSUM BOARD
FIBERBOARD SHEATHING, Celotex Homasote & Other
SHEATHING, FOIL FACED - VENTS
SIDING TYPES, INSTALLATION, DEFECTS
SIDING, ASBESTOS CEMENT
SIDING ASPHALT ROOF SHINGLES on WALLS
SIDING ASPHALT SHINGLE or SHEET
SIDING DAMAGE by SPLASHBACK
SIDING EIFS & STUCCO
SIDING, FIBER CEMENT
SIDING, WOOD PRODUCT CHOICES
SIDING, WOOD INSTALLATION
SIDING WOOD, FAILURES OVER FOAM BOARD
SIDING WOOD, FLASHING DETAILS
SIDING WOOD SHINGLE INSTALLATION
STAIN & BIODETERIORATION AGENT CATALOG
STAINS on & in BUILDINGS, CAUSES & CURES
STAINS on CONCRETE
STAIN DIAGNOSIS on BUILDING EXTERIORS
STAIN DIAGNOSIS on BUILDING INTERIORS
STAINS & FINISHES, INTERIOR
STAIRS, RAILINGS, LANDINGS, RAMPS
STONE SURFACE CLEANING METHODS
STONE VENEER WALLS
STRAW BALE CONSTRUCTION
STUCCO WAll FAILURES DUE TO WEATHER
STUCCO WALL METHODS & INSTALLATION
STUCCO OVER FOAM INSULATION
STUCCO PAINT FAILURES
SURFACE GRADING, SITE DRAINAGE
TEST KITS for DUST, MOLD, PARTICLE TESTS
THERMAL EXPANSION CRACKS in BRICK
THERMAL EXPANSION of HOT WATER
THERMAL EXPANSION of MATERIALS
THERMAL IMAGING, THERMOGRAPHY
THERMAL IMAGING MOLD SCANS
THERMAL MASS in BUILDINGS
VAPOR BARRIERS & CONDENSATION in BUILDINGS
VENTILATION in BUILDINGS
VINYL CHLORIDE HEALTH INFO
VINYL SIDING or WINDOW PLASTIC ODORS
VOCs VOLATILE ORGANIC COMPOUNDS
WALL FINISHES INTERIOR
WALL CONSTRUCTION BARRIER vs CAVITY
WATER BARRIERS, EXTERIOR BUILDING
WATER ENTRY in BUILDINGS
WIND ENERGY SYSTEMS
WIND TURBINES & LIGHTNING
WIND WASHING INSULATION at EAVES
WINDOWS & DOORS
WINTERIZE A BUILDING
Foil-faced building wall sheathing installation:
Do we need to install vent strips behind foil-faced insulating wall sheathing? Is ventilation needed at the top and bottom of exterior walls sheathed with foil-faced insulating board?
Green links show where you are. © Copyright 2015 InspectApedia.com, All Rights Reserved.
Is Venting a Wall Recommended for Exterior Building Walls Covered with Foil-Faced Exterior Sheathing?
Our photo at page top shows a super-insulated building addition constructed by the website author (DJF) in1978. Walls were framed with 2x6 studs, insulated with 6" of fiberglass batts, and sheathed on the wall exterior with 1-inch "High-R" foil-faced foam insulating board.
An additional layer of 15-pound felt was installed over the wall, topped with furring strips to give a 1/4" air space ( for a total wall R-value of about R28) over which we installed plywood T-111 grooved building sheathing. The wall interior surface received a continuous 6-mil poly vapor barrier over which drywall was installed. This was an early experimental "superinsulated" design in response to soaring home heating costs during the U.S. oil price spikes in the 1970's.
By 1983 we heard that concern for possible wall cavity condensation had led manufacturers of foil faced sheathing to recommend corrugated vent strips nailed at the sills and wall top plates to ventilate the insulated wall - an idea that seemed odd at the time, since if we pass outside air behind insulating wall sheathing its insulating value would be wasted. Other reps suggested that vent strips be installed between the exterior sheathing and the insulating board - but that's not where the condensate would occur anyway.
With the benefit of 30+ years of experience with this structure, we have learned that: the felt was unnecessary, no wall vent strips were needed, no moisture condensation has occurred in the walls (where we made test cuts from the interior), and workmanship that included careful sealing around wall penetrations for the electrical boxes was important to keep indoor moisture out of the wall cavities.
The April 1983 Solar Age Magazine addressed the question of whether or not vents are needed behind exterior sheathing when foil faced insulating boards are installed, in Solar Age Magazine Q&A details "Dew Point Dilemmas" that helped resolve these questions. The text below paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.
Wall Vent Strip Question - are they needed?
Wall Vent Strip Use Recommendations with Insulating Wall Sheathing Boards
Evidence of Moisture Penetration into Building Wall Cavities at Penetrations
DJF notes: there was no research actually demonstrating significant air or moisture movement through these butt joints or seams; probably most important are a very good interior vapor and air barrier, especially sealing at wall penetrations, combined with interior moisture control that keeps indoor humidity below excessive levels.
Our photo (left) shows thermal tracking (and possibly mold) around the electrical receptacle in a building wall that combined poor sealing around wall penetrations with high indoor moisture. Even before making a test cut to explore the condition of the wall cavity and its insulation, the marks on three sides of the outlet cover plate tell the story.
The reason we see no moisture and air leak related marks along the left side of this wall outlet - can you guess? Yep - that's the side of the electrical box that was nailed snugly to the wall stud.
as well as VAPOR BARRIERS & CONDENSATION in buildings for details.
Here we include solar energy, solar heating, solar hot water, and related building energy efficiency improvement articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.
Continue reading at HOUSEWRAP / SHEATHING WRAP or select a topic from the More Reading links shown below.
Suggested citation for this web page
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs) about wall sheathing vents
Questions & answers or comments about ventilation requirements behind foil faced building wall sheathing.
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Search the InspectApedia website
HTML Comment Box is loading comments...
Technical Reviewers & References