profile picture
Troubled Houses - The Home Owner's Resourcesm - Air Leaks to Attics 

We see many interesting adverse conditions during our inspections, partly because of the unlimited number of ways people can mess up a house, but also because we do a thorough inspection to reveal these adverse conditions. We hope these stories help home owners avoid these costly conditions by learning about causes, preventions, and remedies. A home purchase can create opportunities for the new owner to improve the home, possibly increasing its value, durability, and usefulness.

NOTICE TO BUYERS & SELLERS: This site does NOT encourage or discourage the purchase of any individual house, or style, age, location, or condition of house.  Conditions shown and/or described in the following articles may have been remedied at the house where these conditions were found.  These conditions typically can be remedied by qualified contractors. The presence of these conditions in any house is comparable to any other real estate consideration such as price, size, or location.  Consult a qualified home inspector before purchasing any house, and consult a qualified real estate agent for more information on how to handle a real estate transaction where adverse conditions are reported in a home inspection.   This site does not describe any house by address or knowingly show a readily identifiable exterior image.  Further, no home actively listed for sale will be described on these pages at the time the article is posted.

Copyright All rights reserved.  "Troubled Houses - The Home Owner's Resource" is a SERVICE MARK of Hankey & Brown Inspection Service Inc.  Topics and all articles in this resource.  Also see our Ice Dams page and our Energy Savers page.

THANK YOU for visiting   Learn more about our services, which now include IR Thermography, radon testing, and carbon monoxide tests.


Typical air leak at a furnace vent 
Large Air leak at a chimney
Air leak between adjoining townhouse units
Multiple air leaks in a story and a half house

Attic bypasses are air leaks from the house to the attic. These air leaks are common in houses built before 1984 and are a major source of energy loss and a major cause of ice dams on the eaves in snowy winters, and often lead to condensation damage to the roof sheathing in houses with high indoor humidity.  The photo shown below is a typical case of a double wall metal "B" vent for a furnace entering an attic through a partition wall cavity without benefit of a sheet metal collar around the vent at the ceiling.  

Without this "draft stop" collar, the vent is essentially a round pipe in a square hole and warm air rises into the attic, even if the gaps around the pipe are covered with insulation. Notice that the yellow insulation near the pipe is dirty.  This insulation actually filtered dust from the air that rose through the opening. 

The typical repair is to have a qualified heating contractor install the metal collar around the pipe to make an air tight fitting at the ceiling, and redistribute the insulation over the collar.
  Air leak, known as an attic bypass, around a furnace vent where it enters the attic from a wall cavity. (C) 2010  ASHI Certified Inspectors, Winter Park, CO 80482 

Huge Air leak from house into attic at the chimney 

    Large attic bypass alongside a fireplace chimney. (C), ASHI Certified Inspectors, Winter Park, CO

The large gap alongside this chimney leaks tremendous quantities of air into the attic.  Simple methods of sealing this gap with sheet metal, then covering it with insulation will significantly cut the home heating costs. Click here to learn more about us.

Find the Heat Loss

   Townhouse Roof snow melt pattern shows heat loss  Troubled Houses (C) 2010 ASHI Certified Home Inspectors in Winter Park, CO

The wall between these two townhouses is not air tight.  Warm air from the bathrooms leaks into the wall between the units and rises to the roof causing the line in the snow. (The oval in the snow is around the right unit's bath vent fan.)  Careful study of roof snow melt patterns can help you locate warm air leaks from your own house.  This only works when the snow layer is uniform and has not been drifted by wind or influenced by shadow patterns.  Sealing the air leaks (attic bypasses) can reduce icing on the eaves (see the longer icicles below the bare spot on the roof) and save energy.  Also see our townhomes page.

Mistakes with insulation and ventilation lead to mold and condensation

 Story and a half house with gable vent into attic. (C) 2011 ASHI Certified Inspectors, Winter Park, CO
This 1940 era story and a half home is typical of thousands similar houses throughout the Twin Cities.  This one unfortunately had several adverse conditions that resulted from misunderstanding the concept of "building envelope" and proper insulation methods for story and a half houses.   Notice the gable louver vent on the front wall.  This vent originally was open to an uninsulated, unconditioned space.  The persons who finished the attic chose to insulate the underside of the roof in the spaces behind the knee walls as shown below.

   Story and a half house with an improperly insulated attic. (C) 2011 ASHI Certified Inspectors, Winter Park, CO
Here you see that both the vertical knee wall (left) AND the underside of the roof (sloped) have been insulated.  If done correctly, either this space would NOT be ventilated, or if ventilated, the roof would not be insulated.  Unfortunately, the gable vent and the roof vents opened into this space, so heat was escaping from the vents.  The interior of the attic is finished with heating ducts on the knee wall.

   Story and a half house with heat ducts placed close to the roof. (C) 2011 ASHI Certified Inspectors, Winter Park, CO 

The snow melt pattern on the roof is consistent with the heat loss where these ducts are tight to the roof.

   Story and a half house with roof snow melt at interior heat ducts. (C) 2011 ASHI Certified Inspectors, Winter Park, CO
Another area of the roof snow cover was disturbed by animal tracks consistent with squirrels accessing the attic from the vines and limbs near the roof.

   Story and a half house with squirrel tracks in roof snow . (C) 2011 ASHI Certified Inspectors, Winter Park, CO

The upper attic revealed the consequences of these conditions.

    Story and a half house attic with squirrel droppings and improper insulation methods. (C) 2011 ASHI Certified Inspectors, Winter Park, CO

The droppings on the light yellow fiberglass insulation are consistent with squirrel feces.  The insulation with the kraft paper backing is upside down (which could trap moisture under the paper).  The white plastic insulation baffle in the roof space permits warm moist air from the area behind the knee wall to rise into the cold upper attic.  Unfortunately this warm moist air condenses on the cold roof surface above the insulation. This has caused white wood rot fungi to grow on the wet surfaces of the roof boards.

   Story and a half house attic with improper insulation methods causing water damage. (C) 2011 ASHI Certified Inspectors, Winter Park, CO

The conditions in this attic are the direct result of a misunderstanding of where to insulate and ventilate.