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 Mobile ViewINSULATION IDENTIFICATION GUIDE INSULATION INSPECTION & IMPROVEMENT ACOUSTICAL SEALANT CHOICESAIR BYPASS LEAKS AIR CHANGE RATE ACH HEAT SAVINGS AIR FILTERS for HVAC SYSTEMS AIR LEAK DETECTION TOOLS AIR LEAK MINIMIZATION AIR LEAK SEALING PROCEDURE AIR SEALING STRATEGIES ANIMAL ALLERGENS APPLIANCE EFFICIENCY RATINGS ASBESTOS FLOORING HAZARD REDUCTION ASBESTOS-FREE INSULATION MATERIALS ASBESTOS IDENTIFICATION IN BUILDINGS ATTIC LEAKS, CONDENSATION & MOLD ATTIC VENTILATION BACKDRAFTING HEATING EQUIPMENT BASEMENT CEILING VAPOR BARRIER BASEMENT HEAT LOSS BASEMENT LEAKS, INSPECT FOR BASEMENT WATERPROOFING BATH & KITCHEN DESIGN GUIDE BATHROOM VENTILATION BIOGAS PRODUCTION & USE BLOWER DOORS & AIR INFILTRATION BLOWER FAN CONTINUOUS OPERATION BLOWER FAN OPERATION & TESTING BLOWN-IN INSULATION BRICK LINED WALLS BRICK VENEER WALL INSULATION BRICK VENEER WALL Loose, Bulged BRICK WALL DRAINAGE WEEP HOLES BUCKLED FOUNDATIONS due to INSULATION? BUILDING NOISE DIAGNOSIS & CURE CATHEDRAL CEILING INSULATION CATHEDRAL CEILING VENTILATION CEILING FINISHES INTERIOR CEILINGS, DROP or SUSPENDED PANEL CEILINGS, PLASTER TYPES CHIMNEY INSPECTION DIAGNOSIS & REPAIR COOLING LOAD REDUCTION by ROOF VENTS COMBUSTION AIR for TIGHT BUILDINGS CONDENSING BOILERS/FURNACES DAMAGE CONDENSATION or SWEATING PIPES, TANKS COOLING LOAD REDUCTION by ROOF VENTS CRAWL SPACES DEFINITION of Heating & Cooling Terms DEHUMIDIFICATION PROBLEMS DEW POINT CALCULATION for WALLS DEW POINT TABLE - CONDENSATION POINT GUIDE DUCT SYSTEM & DUCT DEFECTS REMOTE ELECTRIC POWER, PHOTOVOLTAIC ELECTRIC HEAT ELECTRIC POWER, PHOTOVOLTAIC, REMOTE SITE ENERGY SAVINGS in buildings ENERGY STAR PROGRAM EVAPORATIVE COOLING SYSTEMS FIBERGLASS INSULATION FIBERGLASS HAZARDS FIBERGLASS INSULATION MOLD FLASHING MEMBRANES PEEL & STICK FLAT ROOF MOISTURE & CONDENSATION FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP FLOODS IN buildings-mold FLOOR COVERING for OVER THERMAL MASS SLABS FLOOR TYPES & DEFECTS FLOOR TILE HISTORY & INGREDIENTS FOUNDATION WATERPROOFING FRENCH DRAINS FRAMING DETAILS for BETTER INSULATION FRAMING DETAILS for DOUBLE WALL HOUSES FRAMING METAL STUD PERFORMANCE FREEZE-PROOF A BUILDING FROST HEAVES, FOUNDATION, SLAB GREENHOUSE DESIGN for SOLAR HEATING 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 HEAT TAPES & CABLES on Roofs for Ice Dams HEATING COST SAVINGS METHODS HOT ROOF DESIGNS: Un-Vented Roof Solutions HOUSEWRAP AIR & VAPOR BARRIERS HOUSE DOCTOR, how-to be HUMIDITY LEVEL TARGET ICE DAM PREVENTION INDOOR AIR QUALITY & HOUSE TIGHTNESS INDOOR AIR QUALITY IMPROVEMENT GUIDE INSULATION CHOICES Insulation Air & Heat Leaks INSULATION FACT SHEET- DOE INSULATION for GREENHOUSE or SOLARIUM INSULATION IDENTIFICATION GUIDE INSULATION INSPECTION & IMPROVEMENT INSULATION LOCATION - WHERE TO PUT IT BLOWN-IN INSULATION INSULATION CHOICES INSULATION FACT SHEET- DOE INSULATION LOCATION & QUANTITY for ATTICS INSULATION LOCATION for BASEMENT FLOORS INSULATION LOCATION for BASEMENT WALLS INSULATION LOCATION for BRICK or BLOCK WALL CAVITY INSULATION LOCATION for BRICK VENEER WALLS INSULATION LOCATION for CAPES, CRAWLSPACES INSULATION LOCATION for CATHEDRAL CEILINGS INSULATION LOCATION for GREENHOUSE or SOLARIUM INSULATION LOCATION for PASSIVE SOLAR FLOOR SLAB INSULATION LOCATION & EXTENT for SLABS INSULATION LOCATION for SOUND CONTROL INSULATION LOCATION for SUSPENDED PANELS INSULATION LOCATION for SWIMMING, INDOOR INSULATION MOLD INSULATION R-Values & Properties KIT HOMES, Aladdin, Sears, Wards, Others KITCHEN & BATH DESIGN GUIDE LEED GREEN BUILDING CERTIFICATION LOG HOME ENERGY EFFICIENCY LOG HOME GUIDE LOG HOME WALL INSULATION VALUES METHANE GAS SOURCES MOBILE HOME INSPECTIONS MOISTURE CONTROL in BUILDINGS MOLD in FOAM INSULATION, RESISTANCE MOLD INFORMATION CENTER Nanomaterials Hazards NOISE / SOUND DIAGNOSIS & CURE NOISE CONTROL for HEATING SYSTEMS NOISE CONTROL for FLOORS NOISE CONTROL for PLUMBING NOISE CONTROL for ROOFS ODORS & SMELLS DIAGNOSIS & CURE PAINT FALURE, DIAGNOSIS, CURE, PREVENTION PASSIVE SOLAR DESIGN METHOD PASSIVE SOLAR HEAT PERFORMANCE PASSIVE SOLAR HOME, LOW COST PHOTOVOLTAIC POWER SYSTEMS PLASTER & BEAVERBOARD & DRYWALL PASCAL CALCULATIONS RADIANT BARRIERS RADIANT HEAT RADIANT HEAT Floor Mistakes to Avoid RADIANT HEAT TEMPERATURES RADIANT SLAB FLOORING CHOICES RADIANT SLAB TUBING & FLUID CHOICES REFLECTIVE INSULATION RIGID FOAM USE INDOORS ROOF VENTING ENERGY SAVING DETAILS ROOF VENTING NEEDED? ROOF VENTILATION SPECIFICATIONS ROT, FUNGUS, TERMITES ROT, TIMBER FRAME SEARS KIT HOUSES SHEATHING, FOIL FACED - VENTS SOLAR ENERGY SYSTEMS SOUND CONTROL in buildings STAIN & BIODETERIORATION AGENT CATALOG STAINS on buildings - QUICK GUIDE STAIN DIAGNOSIS on BUILDING EXTERIORS STAIN DIAGNOSIS on BUILDING INTERIORS STAINS on INDOOR SURFACES: PHOTO GUIDE STRESS SKIN INSULATED PANELS STUCCO OVER FOAM INSULATION SWEATING (CONDENSATION) on PIPES, TANKS THERMAL EXPANSION of MATERIALS THERMAL MASS in BUILDINGS THERMAL TRACKING & HEAT LOSS VAPOR BARRIERS & CONDENSATION in BUILDINGS ATTIC CONDENSATION CAUSE & CURE BASEMENT CEILING VAPOR BARRIER CONDENSATION or SWEATING PIPES, TANKS CRAWL SPACE VAPOR BARRIER DEW POINT CALCULATION for WALLS DEW POINT TABLE - CONDENSATION POINT GUIDE FELT 15# ROOFING, as HOUSEWRAP/VAPOR BARRIER HOUSEWRAP AIR & VAPOR BARRIERS 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 VAPOR CONDENSATION & BUILDING SHEATHING WATER BARRIERS, EXTERIOR WOOD SIDING FLASHING DETAILS VENTILATION in BUILDINGS Air Bypass Leaks, Thermal Tracking AIR CHANGE RATE ACH HEAT SAVINGS ATTIC CONDENSATION CAUSE & CURE BALANCED VENTILATION, HEAT COST SAVINGS BATHROOM VENTILATION Blocked Soffit Intake Vents CATHEDRAL CEILING VENTILATION CLOTHES DRYER VENTING COOLING LOAD REDUCTION by ROOF VENTS CRAWL SPACE VENTING & Dryout Procedures HOT ROOF DESIGNS: Un-Vented Roof Solutions HUMIDITY LEVEL TARGET ICE DAM PREVENTION HOUSE DOCTOR, how-to be MOISTURE CONTROL in BUILDINGS ROOF VENTILATION SPECIFICATIONS Roof Venting: Eaves Intake if no Overhang Roof Venting: Soffit Intake Vent-Continuous Roof Venting: Un-Vented Hot Roof Solutions ROOF VENTING ENERGY SAVING DETAILS ROOF VENTING NEEDED? SKYLIGHT VENTILATION DETAILS SOFFIT VENTILATION VENTILATION, BALANCED VENTILATION, BALANCED HEAT COST SAVINGS VENTILATION DESIGN PROBLEMS & SOLUTIONS VENTILATION, EXHAUST ONLY VENTILATION, SUPPLY-ONLY VENTILATION, WHOLE HOUSE STRATEGIES WALL FINISHES INTERIOR WATER BARRIERS, EXTERIOR BUILDING WATER ENTRY in BUILDINGS WIND ENERGY SYSTEMS WIND TURBINES & LIGHTNING WIND WASHING INSULATION At EAVES WINDOWS & DOORS WINTERIZE A BUILDING WOOD, COAL STOVES & FIREPLACES WOOD STOVE SAFETY More Information |
This article describes the best methods for ventilation in a cathedral ceiling and the effects on heat loss of air movement through a ventilated attic or cathedral ceiling. 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. Advice on Venting Cathedral CeilingsThe link to the original Q&A articles in PDF form immediately below is followed by an expanded/updated online version of each article. Accompanying text is reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss. Sketch above showing venting in a steep-slope cathedral ceiling roof is courtesy of Carson Dunlop Readers should see CATHEDRAL CEILING INSULATION and also our concerns with the "hot roof" un-vented cathedral ceiling design discussed at HOT ROOF DESIGNS: Un-Vented Roof Solutions. Also see Roof Venting: Un-Vented Hot Roof Solutions. At INSULATION LOCATION & QUANTITY for ATTICS we discuss the relative benefit of adding insulation to a cathedral ceiling versus building walls in the same area. And see COOLING LOAD REDUCTION by ROOF VENTS. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. The question-and-answer article below paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss. Wind Washing: Does airflow in a vented cathedral ceiling cause unwanted heat loss from the building?
Reply: The Effects on Insulating Value of Airflow Across Fiberglass Insulating Batt SurfacesAnything that induces (causes) airflow through a fiberglass insulating batt will reduce the effectiveness of that insulation, since fiberglass works by reducing air movement. Air flowing across a fiberglass batt, however, should not seriously reduce the insulation's R-value except with very thin batts and very fast air movement. In laboratory experiments, a 3-inch fiberglass batt on an attic floor had a 29-percent reduction in R-value caused by air flowing across it at 2 mph. In another experiment, 6 inches of loose fill fiberglass had a 14 percent reduction at similar airspeeds. With the thicker fiberglass insulating batts in contemporary use, the reductions in insulating value caused by air movement across the fiberglass surface will be less. Also it is unlikely that airflows across insulation in a cathedral ceiling will reach this speed, even under extreme conditions. More details are at COOLING LOAD REDUCTION by ROOF VENTS. Baffle Designs to Stop Airflow Effects Across Insulating Fiberglass Batts in a Cathedral CeilingTo be safe, you could build a baffle such as you suggest, or use manufactured baffles,such as ProperVent. If you are going to the trouble of making your own baffle, use something like perforated foil board (Dennyboard or Thermoply). You will have an effective summertime radiant barrier as well. (See RADIANT BARRIERS). Drywall is probably not an ideal product for an inter-rafter air baffle over the cathedral ceiling insulation since drywall can get soggy if there is excess condensation or a roof leak. Also, unless the drywall were perforated it may trap moisture in the ceiling cavity. At INSULATION LOCATION for CATHEDRAL CEILINGS we describe a high-labor method that combines providing an air barrier above fiberglass insulation in a cathedral ceiling to avoid heat loss by air movement in the roof, combined with the addition of solid foam insulation to provide a much higher R-value for the completed cathedral ceiling structure. -- DF But as Bliss points out in the original Q&A on cathedral ceiling ventilation, the risk of forming a vapor barrier sandwich around fiberglass ceiling insulation (foil faced insulation above and poly vapor barrier below) is that any moisture entering the insulation will be trapped, risking future mold or rot problems. The risk of hidden mold and rot due to moisture entering from the building involves two concepts:
Another possibility would be to perforate the kraft paper on the insulating batts and face the paper up in the roof cavity. Of course you will have to install a continuous poly vapor barrier below the insulation as well. Adequate Air Space over Cathedral Ceiling InsulationIt is unlikely that your proposed 1/2" air space between the top of the fiberglass insulation and the underside of the roof sheathing will provide an effective airflow between the building eaves and ridge. As you'll notice in Carson Dunlop's sketch at the top of this article, experienced home inspectors and other building professionals recommend a 3-inch air space. The question-and-answer article about the effects of airflow on loss of R-value in fiberglass insulating batts, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss. Readers should see COOLING LOAD REDUCTION by ROOF VENTS and see CATHEDRAL CEILING INSULATION and also our concerns with the "hot roof" un-vented cathedral ceiling design discussed at HOT ROOF DESIGNS: Un-Vented Roof Solutions. Also see Roof Venting: Un-Vented Hot Roof Solutions. At INSULATION LOCATION & QUANTITY for ATTICS we discuss the relative benefit of adding insulation to a cathedral ceiling versus building walls in the same area. Use of Radiant Barrier Foil in a Cathedral Ceiling?
Question: Is the foil-based radiant barrier in my cathedral ceiling in a useful place?In my proposed cathedral ceiling detail [sketch at left], I want to use a reflective foil between the insulation and the roof sheathing to double as a radiant barrier and a cathedral ceiling ventilation space liner. Is the radiant barrier in a useful place? James French, Suffern, NY. Reply: Yes but ...The foil is in the right place to block radiant heat across the air space. But there are some other problems. First, radiant barriers are not really cost effective in cold climates. Second, in winter a continuous layer of foil above the insulation in a cathedral ceiling creates a cold-side vapor barrier, vulnerable to condensation on the underside. [Foil has a perm rating of about zero.] In other words, your vapor barrier is in the wrong place and you could end up with trapped moisture, wet insulation, and even rot and mold in the ceiling cavity over time. Most builders and designers feel that a lining material is not necessary in the airspace of a cathedral ceiling except at the eaves [to avoid wind-wash or moved insulation]. At the eaves a rigid baffle is recommended to keep the insulation in place and to keep wind out of the insulation. For extra protection from wind, some builders line the space with a housewrap material such as Tyvek. See RADIANT BARRIERS for details about radiant barriers. Tight Ceiling - Cathedral Ceiling Advice for Venting & MoistureAs explained in Best Practices Guide to Residential Construction, chapter on BEST ROOFING PRACTICES:
Penetrations & Roof Ventilation Challenges - Common Air Leak Points in Ceilings
Original article - PDF:
-- Adapted with permission from Best Practices Guide to Residential Construction. ... Questions & Answers regarding this articleQuestions & answers about the best methods for ventilationg cathedral ceilings and other sloped building ceilings Ask a Question or Search InspectAPediaHTML Comment Box is loading comments...
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