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This article series discusses air bypass leaks, thermal convection loops, voids & leaks in building insulation, including fiberglass, chopped fiberglass, icynene foam, and blown-in cellulose.

Our page top photo shows a void in wall insulation, viewed from a seldom-visited attic. An insulation void such as this one should show up easily during an infrared building scan using thermal imaging. But unless the homeowner thinks of this step, the uninsulated wall may pump heat out of the building for years. Readers should also see AIR BYPASS LEAKS as well as HEAT LOSS in BUILDINGS. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

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Leaky Fiberglass Insulation?

In our Solar Age Magazine article on building heat loss, AIR LEAK DETECTION TOOLS, according to Gadsby from PEP, fiberglass insulation will not block convective loop escape routes for a building's heat: Gadsby's view is that fiberglass does not stop airflow in wall cavities. That article says that infrared scanners tell the same story, showing heat loss around and even through fiberglass insulation--even the massive batts in a superinsulated ceiling. For that reason, the PEP partners prefer blown insulation over fiberglass batts. With loose-fill fiberglass insulation, they believe, the airflow paths are circuitous enough to stop short any airflow. Our photo (above left) shows the black stains deposited by dust particles (this is not mold) when building air leaks past fiberglass insulation, seen from the attic side of a 1960's contemporary framed home with lots of air leaks. In our photo and in many air leak problems at fiberglass-batt insulated cavities, the problem is one of installation and construction leak problems, not a defect in the fiberglass insulating batt itself. OPINION-DJF: we pose that loose-fill insulation may do a more consistent job of closing air or thermal bypass leaks that are sometimes left around fiberglass batts - that's the real problem. Looking at an IR scan that shows heat loss "through" an insulating batt, if combined with visual inspection, using invasive cuts if necessary, will, we predict, show air bypass leaks, other insulation installation errors, or insulation wet from building leaks. Otherwise we should not see large solid areas of no-leaks on IR scans of walls and ceilings that have tightly-installed batts, no voids, and no penetrations.

The claim of fiberglass batt air leakage, supported vigorously by the foam insulation industry, is equally vigorously counter-argued by the fiberglass insulation companies who point out that properly installed the air flow rate through the fiberglass itself in fiberglass insulated cavities is very low.

OPINION-DJF: air leaks around insulating batts that are not snugly fit between building framing members or where openings have been cut for ceiling lights, electrical boxes, plumbing chases, and voids left from workers who move or remove insulation appear from visual inspection to be the prime culprit, rather than air movement through the fiberglass insulating batt itself.

Our attic photo (left) shows both air bypass leaks (black stains on the fiberglass batt at center-left of the photo) and an insulation void (above the bath vent fan).

Where air leaks occur around fiberglass batts, look closely: you will probably see that the leaks are at the perimeter of the insulation and at locations where openings in framing, drywall, or insulation were cut to admit recessed ceiling lights, electrical or plumbing penetrations, or similar openings.

If airflow were simply through the fiberglass batt in any uniform way, the dust stains on and inside the insulation would also be expected to be uniform. They are not.

See Air Bypass Leaks, Thermal Tracking for details.

Leaky Icynene Foam Insulation?

We full agree with PEP, however, that predicting air leaks through fiberglass-insulated cavities is very difficult, since leakage depends on the quality of installation workmanship. We have indeed occasionally found workmanship errors that resulted in unanticipated air leaks though foam-sprayed insulation as well, particularly when the insulation (of either type) was installed in a hard-to-access space such as a crawl area.

Our pair of photos above were taken in a tight, hard to enter crawl area where the icynene spray foam insulation was not so carefully applied. Our smoke test found air movement from the damp, occasionally moldy crawl area into an opening in the foam insulating blanket. We pulled a bit of this already-leaky material off to see what was behind and found (photo above right) a leaky metal return air duct. When the air handler was running it was drawing cold, sometimes nasty, crawl space air into the duct system through this leak. Take a look at our foam retrofit photo at left. We noticed two impressive details: a flood of foam entered this attic space over the un-heated garage (the insulator just pumped away, thinking he was foaming into an enclosed wall cavity). But at the photo's upper right we see a shiny metal foil surface (a pre-existing radiant barrier) but no insulation whatsoever. See Icynene Foam Spray Insulation for more information on icynene foam insulation.

Leaky Cellulose Building Insulation?

Our photo (left) shows a very large void in the building attic's blanket of blown-in cellulose insulation where no provision was made to insulate around a chimney chase. Blown-in building insulation is often packed tightly between building framing members and other surfaces, and is likely to pose fewer air bypass leaks than sloppily-installed fiberglass batts (discussed above). But precisely because blown-in cellulose is often selected for an insulation retrofit in older homes that may have had little or even no insulation previously, there is the risk that the insulator fails to notice and handle trouble spots such as the one shown in our photo. Chopped-fiberglass blown-in insulation, and any pumped or blown insulating product that is sent into building cavities where there is no direct view all face the risk of unexpected voids. For example in post-and-beam structures and converted barns, experienced retrofit insulation contractors have learned to watch out for the wall framing blockage formed by diagonal bracing. The contractor will drill extra openings to be sure that no insulation voids are left in the building walls. See Cellulose loose fill insulation for more information.

How to Find Points of Heat Loss & Building Air Leaks

The article HEAT LOSS DETECTION TOOLS explains how to survey a building for air and heat loss or gain points and how to correct them. Just below are links to images of pages from "House Doctors with Better Medicine, Princeton Energy Partners use the latest diagnostic tools to comb a house for the major causes of heat loss. Their findings are often astonishing. Their strong prescriptions bring results", Steven Bliss, rom Solar Age Magazine.

In this article the author, Steven Bliss, accompanies a building weatherization and energy-savings company through a detailed building inspection for heat loss points, convective loops, and air leaks. The author accompanies Princeton Energy Partners as they use thermal imaging, smoke guns, and visual inspection to pinpoint building air leaks, heat loss points, air infiltration and air exfiltration on a building. The importance of setting priorities for sealing these points of energy wasted is emphasized and discussed, and sketches as well as photographs of common points of building heat loss, or unwanted heat gain, and air leaks are provided.

• Building Heat Loss & Air Leaks - use your browser's back button to return to this page
• Building Heat Loss & Air Leaks - part 2
• Building Heat Loss & Air Leaks - part 3
• Building Heat Loss & Air Leaks - part 4

The text above significantly expands, and also paraphrases, quotes-from, and comments an original article, "House Doctors with Better Medicine", Steven Bliss, (see links just above) from Solar Age Magazine.

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AIR CONDITIONING & HEAT PUMP SYSTEMS
ENERGY SAVINGS in BUILDINGS
INSULATION & VENTILATION INSPECTION & IMPROVEMENT
INTERIORS of BUILDINGS
ACOUSTICAL SEALANTS
AGE of a BUILDING - how to determine
AIR BYPASS LEAKS
AIR LEAK DETECTION TOOLS
  Find Heat Loss & Air Leaks
  Heat Loss Investigation Sequence
  Blower Door Test Data Results
  Smoke Gun for Air Leaks
  Attic Energy Losses - InfraRed
  Basement Energy Losses- IR & Visual
  Duct System Air Movement
  Living Space Heat Loss
  Targets & Hidden Leak Points
  Convective Loops & Thermal Bypass Leaks
  Insulation Air & Heat Leaks
  The Bottom Line on Energy Retrofits
AIR LEAK MINIMIZATION
AIR SEALING STRATEGIES
ANIMAL ALLERGENS
ASBESTOS IDENTIFICATION IN BUILDINGS
ATTIC LEAKS, CONDENSATION & ATTIC MOLD
ATTIC VENTILATION
BASEMENT HEAT LOSS
BASEMENT LEAKS Moisture or Mold
BASEMENT WATERPROOFING
BATHROOM VENTILATION
BLOWER DOORS & AIR INFILTRATION
BRICK LINED WALLS
BUCKLED FOUNDATIONS due to INSULATION?
CATHEDRAL CEILING INSULATION
CHIMNEY INSPECTION DIAGNOSIS & REPAIR
COMBUSTION AIR for TIGHT BUILDINGS
CRAWL SPACES
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
ELECTRICAL INSPECTION, DIAGNOSIS, REPAIR
ENERGY SAVINGS in BUILDINGS
ENERGY SAVINGS PRIORITIES
ENERGY SAVINGS RETROFIT CASE STUDY
ENERGY SAVINGS RETROFIT LEAK SEALING GUIDE
ENERGY SAVINGS RETROFIT OPTIONS
ENVIRONMENTAL HAZARDS
FIBERGLASS INSULATION
FIBERGLASS HAZARDS
FIBERGLASS MOLD
FIREPLACE Damage & Unsafe Hearths - Settlement
FLAT ROOF MOISTURE & CONDENSATION
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FLOODS IN BUILDINGS-mold
FLOORING TYPES & DEFECTS
FOUNDATION WATERPROOFING
FRAMING DETAILS for BETTER INSULATION
FRAMING DETAILS for DOUBLE WALL HOUSES
FREEZE-PROOF A BUILDING
HEAT LOSS in BUILDINGS
HEAT LOSS DETECTION TOOLS
  Find Heat Loss & Air Leaks
  Heat Loss Investigation Sequence
  Blower Door Test Data Results
  Smoke Gun for Air Leaks
  Attic Energy Losses - InfraRed
  Basement Energy Losses- IR & Visual
  Duct System Air Movement
  Living Space Heat Loss
  Targets & Hidden Leak Points
  Convective Loops & Thermal Bypass Leaks
  Insulation Air & Heat Leaks
  The Bottom Line on Energy Retrofits
HEAT LOSS INDICATORS
HEAT LOSS R U & K VALUE CALCULATION
Heat Tapes: Use on Roofs for Ice
HEATING COST SAVINGS METHODS
HOUSEWRAP AIR & VAPOR BARRIERS
HUMIDITY LEVEL TARGET
ICE DAM PREVENTION
Ice Dams: Comparing Two Houses
INSULATION CHOICES
INSULATION FACT SHEET- DOE
INSULATION IDENTIFICATION GUIDE
INSULATION LOCATION for BASEMENTS
INSULATION LOCATION for CAPES, CRAWLSPACES
INSULATION for GREENHOUSE or SOLARIUM
INSULATION MATERIAL IDENTIFICATION GUIDE
INSULATION MOLD
INSULATION R-Values & Properties
INSULATION & VENTILATION INSPECTION & IMPROVEMENT
  ATTIC CONDENSATION CAUSE & CURE
  Air Bypass Leaks, Thermal Tracking
  Blocked Soffit Intake Vents
  BRICK VENEER WALL INSULATION
  CATHEDRAL CEILING INSULATION
  ENERGY SAVINGS in BUILDINGS
  ENERGY SAVINGS PRIORITIES
  ENERGY SAVINGS RETROFIT CASE STUDY
  ENERGY SAVINGS RETROFIT LEAK SEALING GUIDE
  ENERGY SAVINGS RETROFIT OPTIONS
  FRAMING DETAILS for BETTER INSULATION
  FRAMING DETAILS for DOUBLE WALL HOUSES
  Inspect Attics for Moisture or Mold
  Inspect Basements for Moisture or Mold
  Inspect Building Exterior
  Inspect the Ridge Vent System from the Attic
  Inspect the Soffit Vent System from the Attic
  Insulation Air & Heat Leaks
  INSULATION R-Values & Properties
  Insulation Values of Log Home Walls
  POLYISOCYANURATE FOAM INSULATION
  POLYSTYRENE FOAM INSULATION
  RADIANT BARRIERS
  RIGID FOAM USE INDOORS
  Urea Formaldehyde Foam Insulation UFFI
  URETHANE FOAM Deterioration, Outgassing
  Vermiculite Insulation
LOG HOME GUIDE
MOBILE HOME INSPECTIONS
MOISTURE CONTROL in BUILDINGS
Mold Growth Resistance of Foam Insulation
MOLD INFORMATION CENTER
ODORS & SMELLS DIAGNOSIS & CURE
PAINT FALURE, DIAGNOSIS, CURE, PREVENTION
PLASTER & BEAVERBOARD & DRYWALL
RADIANT BARRIERS
RADIANT HEAT
RADIANT HEAT Floor Mistakes to Avoid
RADIANT SLAB FLOORING CHOICES
RADIANT SLAB TUBING & FLUID CHOICES
ROOF VENTILATION SPECIFICATIONS
ROT, FUNGUS, TERMITES
ROT, TIMBER FRAME
SAFETY HAZARDS & INSPECTIONS
SEARS KIT HOUSES
SOLAR ENERGY SYSTEMS
SOUND CONTROL in BUILDINGS
STAIN DIAGNOSIS
STAIRS, RAILINGS, LANDINGS, RAMPS
STUCCO OVER FOAM INSULATION
STRUCTURAL INSPECTIONS & DEFECTS
SUMP PUMPS GUIDE
THERMAL EXPANSION of MATERIALS
THERMAL MASS in BUILDINGS
THERMAL MASS in UPSTAIRS
THERMAL TRACKING & HEAT LOSS
  Ceiling Thermal Tracking Marks
  Wall Thermal Tracking Stains
  Floor Carpet Thermal Tracking Stains
  Air Bypass Leaks Marks on Insulation
  Thermal Tracking to Diagnose IAQ
  Stains HVAC Supply Registers
  Pet Stains on Floors
  Pet Stains on Walls
  Human Occupant Stains on Walls
  Stains from Candles, Woodstoves, Fireplaces
  Other Stains on Indoor Walls & Ceilings
  What to Do About Thermal Tracking
VAPOR BARRIERS & AIR SEALING at BAND JOISTS
VAPOR BARRIERS & CONDENSATION in BUILDINGS
VAPOR BARRIERS & HOUSEWRAP
VAPOR CONDENSATION & BUILDING SHEATHING
VENTILATION in BUILDINGS
WATER ENTRY in BUILDINGS
WIND TURBINES
WINDOWS & DOORS
WINTERIZE A BUILDING
WOOD Burning Heaters Fireplaces Stoves

• Solar Age Magazine was the official publication of the American Solar Energy Society. The contemporary solar energy magazine associated with the Society is Solar Today. "Established in 1954, the nonprofit American Solar Energy Society (ASES) is the nation's leading association of solar professionals & advocates. Our mission is to inspire an era of energy innovation and speed the transition to a sustainable energy economy. We advance education, research and policy. Leading for more than 50 years. ASES leads national efforts to increase the use of solar energy, energy efficiency and other sustainable technologies in the U.S. We publish the award-winning SOLAR TODAY magazine, organize and present the ASES National Solar Conference and lead the ASES National Solar Tour – the largest grassroots solar event in the world."
  
• Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education. Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
  Excerpts with updates and annotations expanding the original Best Practices Guide text can be found in the online review and book summary at BEST CONSTRUCTION PRACTICES GUIDE and also at DECK & PORCH CONSTRUCTION, at INDOOR AIR QUALITY IMPROVEMENT GUIDE, and in other articles found at InspectAPedia.com such as HOUSEWRAP AIR & VAPOR BARRIERS, SOUND CONTROL in BUILDINGS, and other topics.
• Ice Dam Leaks in building attics and roof cavities, how to inspect for evidence of leaks, identify causes, and correct bad attic ventilation, improper roof venting, and these causes of attic mold or roof structure damage

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