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This article explains how to spot attic ventilation defects in the soffits or building eaves, as visible from the attic or building interior.
This soffit venting discussion is part of "How to Correct Improper or Inadequate Attic or Under-Roof Ventilation in buildings", our discussion of "Attic Condensation".
This article 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.
Inspecting the Soffit or Eaves Vent System from the Attic - look for blockage
Inspecting in the building attic, we check to be sure that there is good air flow at the lower roof edges or "eaves". Even when we see apparent vents installed outside, such as soffit vent strips or perforated soffit covering material, the venting may be blocked or otherwise inadequate.
The cost to heat and cool a building is increased and the risk of an under-roof rot or mold problem is increased as well if the roof is not properly designed and vented.
For example, installing exit venting a the ridge without installing adequate intake venting at the building eaves will increase heat loss from the building during winter months. Warm air leaking into the attic or roof cavity from the building creates a convection current of rising air in the building.
When the convection current of warm moist air leaving at the ridge vent is unable to draw dry cool outdoor air into the under-roof space at the building eaves or lower roof edges, it tends to draw more heated air out of the living space.
Look for these insulation and ventilation defects a the building eaves or lower roof edges:
Inadequate or incomplete insulation in the attic floor or knee walls.
Insulation up tight against the roof decking - blocking air flow there, no air path along roof sheathing or decking
Moisture stains from ice dam leaks or roof leaks, found on rafters and roof sheathing, particularly at the lower roof edges over a poorly-insulated or poorly-vented attic or cathedral ceiling
Bath vents or kitchen vents that spill moist air into the attic rather than directing it outdoors; vent fan ducts that are not insulated and that slope so that their interior condensate leaks back into the building.
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"Energy Savers: Whole-House Supply Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Supply_Vent.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11880?print
"Energy Savers: Whole-House Exhaust Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Exhaust.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11870
"Energy Savers: Ventilation [copy on file as /interiors/Energy_Savers_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Natural Ventilation [copy on file as /interiors/Energy_Savers_Natural_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Energy Recovery Ventilation Systems [copy on file as /interiors/Energy_Savers_Energy_Recovery_Venting.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11900
"Energy Savers: Detecting Air Leaks [copy on file as /interiors/Energy_Savers_Detect_Air_Leaks.pdf ] - ", U.S. Department of Energy
"Energy Savers: Air Sealing [copy on file as /interiors/Energy_Savers_Air_Sealing_1.pdf ] - ", U.S. Department of Energy
Humidity: What indoor humidity should we maintain in order to avoid a mold problem?
"Weather-Resistive Barriers [copy on file as /interiors/Weather_Resistant_Barriers_DOE.pdf ] - ", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
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The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
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