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Troubled Houses - The Home Owner's Resourcesm - Air Leaks
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.
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TOPICS
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.
Huge Air leak from house into attic at the chimney
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
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
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.
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.
The snow melt pattern on the roof is consistent with the heat loss where these ducts are tight to the roof.
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.
The upper attic revealed the consequences of these conditions.
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.
The conditions in this attic are the direct result of a misunderstanding of where to insulate and ventilate. A more appropriate method is shown below.
Either method A or B would have worked in this case, but the installer mixed the methods. The result is an inefficient installation that is causing to ice dams at the eaves and water damage in the upper attic. Return to top of topic list.
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