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 Mobile ViewENERGY SAVINGS in BUILDINGS INSULATION IDENTIFICATION GUIDE INSULATION INSPECTION & IMPROVEMENT INTERIORS AIR BYPASS LEAKS AIR LEAK DETECTION TOOLS AIR LEAK MINIMIZATION AIR LEAK SEALING PROCEDURE AIR SEALING STRATEGIES ASBESTOS IDENTIFICATION IN BUILDINGS ATTIC LEAKS, CONDENSATION & MOLD BASEMENT WATERPROOFING CRAWL SPACES CRAWL SPACE DRYOUT PROCEDURES CRAWL SPACE GROUND COVERS CRAWL SPACE INSULATION RETROFIT CRAWL SPACE SAFETY ADVICE CRAWL SPACE VAPOR BARRIER CRAWLSPACE MOLD ADVICE MOLD CLEANUP by MEDIA BLASTING MOLD ON DIRT FLOORS SUMP PUMPS CONDENSATION or SWEATING PIPES, TANKS COOLING LOAD REDUCTION by ROOF VENTS DEHUMIDIFICATION PROBLEMS DEW POINT CALCULATION for WALLS DEW POINT TABLE - CONDENSATION POINT GUIDE EARTHQUAKE DAMAGED FOUNDATIONS EFFLORESCENCE, Salts & White / Brown Deposits ENERGY SAVINGS in BUILDINGS FIBERGLASS INSULATION FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP FLOOD DAMAGE TO FOUNDATIONS FLOOR TYPES & DEFECTS FOUNDATION WATERPROOFING FRENCH DRAINS FREEZE-PROOF A BUILDING FROST HEAVES, FOUNDATION, SLAB HEAT LOSS in buildings HEAT LOSS DETECTION TOOLS HEAT LOSS INDICATORS HEAT LOSS PREVENTION PRIORITIES HEAT LOSS R U & K VALUE CALCULATION HEAT LOSS RATE CALCULATIONS HOUSEWRAP AIR & VAPOR BARRIERS HUMIDITY LEVEL TARGET HOUSEWRAP INSTALLATION DETAILS ICE DAM PREVENTION INSULATION IDENTIFICATION GUIDE INSULATION INSPECTION & IMPROVEMENT LEAD POISONING HAZARDS GUIDE MOBILE HOME INSPECTIONS MOLD CLEANERS - WHAT TO USE MOLD CLEANUP COMPANIES MOLD CLEANUP, DO IT YOURSELF MOLD CLEANUP GUIDE- HOW TO GET RID OF MOLD ODORS & SMELLS DIAGNOSIS & CURE ROT, FUNGUS, TERMITES STAIN DIAGNOSIS on BUILDING INTERIORS STRUCTURAL INSPECTIONS & DEFECTS SUMP PUMPS SEPTIC SYSTEM PUMPS Sump Pump Discharge Sump Pump Inspection Sump Pump Types Submersible Sump Pump Guide Pedestal Type Sump Pump Guide Battery Backup Sump Pump Choices Water Powered Sump Pump Guide Sump Pump Single vs Duplex SWEATING (CONDENSATION) on PIPES, TANKS THERMAL TRACKING Indicates Heat Loss VAPOR BARRIERS & CONDENSATION in BUILDINGS ATTIC CONDENSATION CAUSE & CURE BASEMENT CEILING VAPOR BARRIER CRAWL SPACE VAPOR BARRIER FELT 15# ROOFING, as HOUSEWRAP/VAPOR BARRIER HOUSEWRAP INSTALLATION DETAILS HOUSEWRAP PRODUCT CHOICES HOUSEWRAP at SILLS, SOLES, TOP PLATES HUMIDITY LEVEL TARGET MOISTURE CONTROL in BUILDINGS RAIN SPLASH-UP SIDING DAMAGE VAPOR BARRIERS & AIR SEALING at BAND JOISTS VAPOR BARRIERS & CONDENSATION in BUILDINGS VAPOR BARRIERS & HOUSEWRAP Leaks into vinyl-sided building Select & Use House Wrap Code Requirements for Building Wrap Sheathing Wrap Performance Measures Water Resistance of Housewraps Air Infiltration of Housewraps Performance Table for Housewraps Can the Vapor Barrier be Omitted? VAPOR CONDENSATION & BUILDING SHEATHING WOOD SIDING FLASHING DETAILS WATER BARRIERS, EXTERIOR VENTILATION in BUILDINGS WATER ENTRY in buildings ATTIC LEAKS Moisture or Mold BARRIERS, EXTERIOR WATER BASEMENT CEILING VAPOR BARRIER BASEMENT De-Watering Systems BASEMENT HEAT LOSS BASEMENT LEAKS, INSPECT FOR BASEMENT WATERPROOFING BASEMENT WATER ENTRY PREVENTION CATCH BASINS Chimney Leaks CONDENSATION or SWEATING PIPES, TANKS CONDENSATION on WINDOWS & SKYLIGHTS CORROSION in ELECTRICAL PANELS CRAWL SPACE DRYOUT PROCEDURES DEW POINT CALCULATION for WALLS DEW POINT TABLE - CONDENSATION POINT GUIDE DRYER VENTING DRYWELLS, FRENCH DRAINS for FLAT SITES DRYWELL DESIGN & USES EFFLORESCENCE, Salts & White / Brown Deposits ELECTRIC PANEL MOISTURE EXTERIOR WATER SOURCE ELIMINATION FLOOD Damage Assessment & Repairs FLOOD DAMAGED FOUNDATIONS FLOOD VENTS & FLOOD PORTS FLOODS IN buildings-priorities FOUNDATION DRAINS, INTERIOR FOUNDATION WATERPROOFING GEOTEXTILES & DRAINAGE MATS GRADING & SITE WORK, EXTERIOR GUTTERS & DOWNSPOUTS HUMIDITY CONTROL & TARGETS INDOORS HOUSEWRAP AIR & VAPOR BARRIERS LOG HOME Leak Diagnosis & Cure LOG HOME Condensation &Moisture MOISTURE in BUILDING WALLS, EFFECTS MOISTURE in CELLULOSE INSULATION MOISTURE CALCULATIONS MOISTURE CONTROL in BUILDINGS MOISTURE METER STUDY MOISTURE PROBLEMS: CAUSE & CURE MOLD in buildings MOLD PREVENTION AFTER FLOODING MOLD RESISTANT CONSTRUCTION PERIMETER DRAIN SYSTEMS ROOF VENTILATION SPECIFICATIONS Soffit Intake Vents & Attic Condensation SEALERS, Basement Floor & Wall Moisture SEWAGE CONTAMINATION SITE & SURFACE DRAINAGE SUMP PUMPS GUIDE SWEATING (CONDENSATION) on PIPES, TANKS VENTILATION in BUILDINGS VENTILATION DESIGN PROBLEMS & SOLUTIONS VENTILATION, WHOLE HOUSE STRATEGIES WATER ENTRY in BUILDINGS WET BASEMENT PREVENTION WINDOW / DOOR AIR LEAK SEALING HOW TO Window Flashing & Sealing Guide WINDOW LEAKS INTO BASEMENT WINTERIZE A BUILDING More Information |
Which way does the insulation vapor barrier or kraft paper go over a basement or crawl space: facing up (towards the floor above) or facing down (towards the crawl space or basement floor)? This article discusses the proper location and placement of moisture barriers or vapor barriers in crawl spaces to crawl space moisture. Does the vapor barrier go "up" towards the warm side or underside of the floor above, or does the vapor barrier go "down" facing the crawl space or basement interior? And what difference does it make to building moisture problems? InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.© Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website. Crawl Space Ground Covers to Help Control Crawl Space MoistureReaders dealing with damp or wet crawl spaces should start reading at CRAWL SPACE DRYOUT PROCEDURES. If your crawl space has a dirt floor or a damp or wet floor also see CRAWL SPACE GROUND COVERS and MOLD ON DIRT FLOORS. Accompanying text is reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss. Our page top sketch showing the effects of covering a dirt floor in a crawl space is courtesy of Carson Dunlop. Carson Dunlop's comment that a dirt crawl can contribute several gallons of moisture per day into a home is the best case. If the crawl area is actually wet from surface runoff, roof spillage, ground water, or plumbing leaks, the amount of water pumped into the home can be much larger and more harmful. The link to the original Q&A article in PDF form immediately below is followed by an expanded/updated online version of this article.
The question-and-answer article below paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss. How Best to Control Crawl Space MoistureQuestion: If you place a vapor barrier on the warm side of the insulation between a heated area and an unheated crawlspace, will moisture from the crawlspace migrate into the insulation and condense? In the winter, when the house is hot and dry, it seems the vapor barrier should be on the cold side of the insulation. John Mascaro, Mascaro Construction, Philadelphia PA Answer: How Moisture Moves in Buildings
Since warm air holds more moisture than cold air, warmer air generally has the higher vapor pressure. For example, air at 68 degF. at or above 33-percent relative humidity (RH) will have a higher vapor pressure than crawlspace air at 40 degF and 90-pecent relative humidity (RH), and moisture will tend to move, if at all, from the warmer house to the cooler crawlspace. Using a cold-side vapor barrier would almost guarantee moisture condensation in the insulation in winter - a very undesirable condition that reduces the effectiveness of the insulation and is just asking for a mold contamination problem. Our horrible crawlspace (above) shows foil-faced fiberglass insulation installed with the vapor barrier facing "down" towards the wet crawlspace floor - this is an example of backwards, incorrect, "cold-side" vapor barrier installation that invites moisture condensation and even mold contamination (see Mold in Fiberglass Insulation) inside the fiberglass insulation. It is easier to retrofit-add crawlspace insulation this way since we are tempted to just push the insulation up between the floor joists and use the vapor barrier or kraft facing to staple the insulation in place. Notice that the crawlspace insulation is falling down? Stapling insulation up through the foil facing to the underside of the floor joists in this location didn't work. The insulation in the crawlspace in our photo should have been installed with the kraft or foil facing "up" towards the warm area or against the underside of the subfloor overhead. Using that method, insulation is supported in place by spring-wire that is simply placed at intervals between facing sides of floor joists. Moisture Movement from Crawlspace into House InteriorIn the summer, however, particularly in air-conditioned homes, moisture may be driven from the crawlspace into the house. Although you could stop this by using a vapor barrier below the under-floor insulation (presumably insulation has been placed under the floor over the crawl area), it is more practical to keep the crawlspace RH level down. This is best done with a polyethylene ground cover (see CRAWL SPACE GROUND COVERS), and by making sure that there are no outside water leaks nor plumbing leaks into the crawl space. If you see moisture stains on the crawlspace walls, it is at least sometimes a source of un-wanted building moisture. Even if you think your crawlspace is "dry" it might not be. EFFLORESCENCE, Salts & White / Brown Deposits provides examples of visual clues that moisture is being pumped through foundation walls or up through a dirt floor into the building even when actual crawlspace flooding is not occurring. Air Movement from Crawlspace to House InteriorMuch of the moisture transport from crawlspace into house is due to the stack effect (or air convection currents) pulling air up through the house. Warm air tends to rise upwards through a building, and that air movement will be even more rapid if upper floor windows are open or attic or upper floor exhaust fans are in operation. If a crawlspace is damp, wet, moldy, or contaminated by a sewage spill, all of those undesirable ingredients are easily transported from the crawlspace into the occupied space from the crawl area, riding on rising air convection currents. In fact we [DF] have found frequent evidence that moisture from a wet basement or crawl space has produced excessive levels of condensation all the way up in a building's attic. The best way to prevent un-wanted air movement from a crawlspace into a building is to seal off all air leaks between the crawlspace and the house. See AIR SEALING STRATEGIES for details about sealing building air leaks. A good ground cover in the crawlspace will also keep the RH of any crawlspace air that does enter the house reasonably low. See CRAWL SPACE GROUND COVERS for details on adding crawlspace ground covers. For a more technical explanation of condensation in buildings, also see DEW POINT TABLE - CONDENSATION POINT GUIDE and DEW POINT CALCULATION for WALLS. Key building water entry diagnosis and cure articles:
The question-and-answer article about use of a plastic barrier on crawl space floors to control crawl space moisture and mold, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss. Questions & Answers regarding this articleAsk a Question or Search InspectAPediaHTML Comment Box is loading comments...
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