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VENTILATION in BUILDINGS
AIR BYPASS LEAKS
AIR LEAK DETECTION TOOLS
AIR LEAK SEALING PROCEDURE
AIR POLLUTANTS, COMMON INDOOR
AIR SEALING STRATEGIES
BASEMENT CEILING VAPOR BARRIER
BASEMENT HEAT LOSS
BASEMENT LEAKS, INSPECT FOR
BLOWER DOORS & AIR INFILTRATION
BRICK WALL DRAINAGE WEEP HOLES
CATHEDRAL CEILING VENTILATION
CEILINGS, DROP or SUSPENDED PANEL
COMBUSTION AIR for TIGHT BUILDINGS
COOLING LOAD REDUCTION by ROOF VENTS
CONDENSATION on WINDOWS & SKYLIGHTS
DEW POINT CALCULATION for WALLS
FIREPLACES & HEARTHS
FLAT ROOF MOISTURE & CONDENSATION
GREEN BUILDING CONSTRUCTION
HEAT LOSS in BUILDINGS
HEAT LOSS DETECTION TOOLS
HEAT RECOVERY VENTILATORS
HOT ROOF DESIGNS: UN-VENTED ROOF SOLUTIONS
HOUSEWRAP AIR & VAPOR BARRIERS
HOUSE DOCTOR, how-to be
HUMIDITY LEVEL TARGET
ICE DAM LEAKS
INDOOR AIR HAZARDS TABLE
INDOOR AIR QUALITY & HOUSE TIGHTNESS
INDOOR AIR QUALITY IMPROVEMENT GUIDE
INSULATION AIR & HEAT LEAKS
INSULATION INSPECTION & IMPROVEMENT
INSULATION R-VALUES & PROPERTIES
LOG HOME GUIDE
MOISTURE CONTROL in BUILDINGS
ODORS GASES SMELLS, DIAGNOSIS & CURE
ROOF VENTILATION SPECIFICATIONS
ROOF ICE DAM LEAKS
SHEATHING, FOIL FACED - VENTS
STAIN DIAGNOSIS on BUILDING INTERIORS
STUCCO WALL METHODS & INSTALLATION
SWEATING (CONDENSATION) on PIPES, TANKS
THERMAL MASS IN BUILDINGS
THERMAL TRACKING Indicates Heat Loss
VAPOR BARRIERS & AIR SEALING at BAND JOISTS
VAPOR BARRIERS & HOUSEWRAP
VAPOR CONDENSATION & BUILDING SHEATHING
VENTILATION in BUILDINGS
WIND WASHING INSULATION At EAVES
WINDOWS & DOORS
This article explains How to Correct Improper or Inadequate Attic or Under-Roof Ventilation at skylights, This article on the design of proper venting around roof skylights is part of our series of articles about ATTIC CONDENSATION CAUSE & CURE.
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This article series describes inspection methods and clues to detect roof venting deficiencies, insulation defects, and attic condensation problems in buildings. It describes proper roof ventilation placement, amounts, and other details.
These recommendations are based on a survey of building science literature combined with 30 years of building inspections, on the observation of the locations of moisture, mold, ice dams, condensation stains, and other clues in buildings, and on the correlation of these clues with the roof venting conditions at those properties.
We have measured very large changes in airflow, temperature, and moisture before and after installing roof venting.
As described in Best Practices Guide to Residential Construction:
Localized hot spots such as skylights can also lead to ice dams below, due to blocked ventilation as well as melt water from skylight heat loss.
Notching the rafters on either side of the skylight will help maintain airflow above the skylight (Figure 2-59 at left).
As a backup to prevent leaks at skylights, during skylight installation and even though modern skylights are usually provided with a factory-built flashing and counterflashing, it is always a good idea to seal the skylight curb and surrounding roof area with a bituminous membrane (see Figure 2-5 at left).
Also see Ice Dam Protection for Skylignts for cases where under-roof venting is not provided around a skylight.
Cathedral Ceiling Ventilation Alongside of Skylights
Cathedral ceilings require the same continuous air barriers, and balanced soffit and ridge vents, as attics.
Both air sealing and ventilation are more critical, however, since any trapped moisture in the roof cavity will remain longer and potentially cause greater damage than in an open attic.
Also, since there is little or no communication from bay to bay, an effective ventilation system must reach every bay (Figure 2-57 at left).
-- Adapted with permission from Best Practices Guide to Residential Construction.
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