Here is the independent inspectors report
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The subject of this report will be named the ‘ice event’
Reason for the inspection and the report:
1. Attempt to verify that the work performed by the seller was done right.
2. The cause of the ‘ice event’ needed to be determined so corrective action can be taken if necessary so it doesn’t happen again.
About the ‘type’ of inspection:
The inspection was limited to non-invasive techniques. I used a thermal imaging device to look for temperature differences on the surface of the drywall that might indicate water within the wall, and I used visual inspection.
What was found:
Thermal imaging did not detect any temperature differences of the interior surface of the drywall that might be interpreted as water in the drywall or water in the wall cavity.
Visual inspection of the attic floor, near the exit of the dryer vent, showed evidence that a little water had been there (ponding), but the majority of the current wetting was on the gable sheathing.
Visual inspection of the surface of the wall sheathing, (the OSB) near where the ‘ice event’ happened, visible from the garage attic, showed no evidence of water. Visual inspection found a broken dryer vent in the attic. The aluminum duct of the dryer vent was detached from the plastic flapper assembly.
Results of the inspection:
Encouraging, but not conclusive.
1. Only invasive inspection of the area can be conclusive to determine whether or not there
is moisture in the wall cavity(s).
2. I am fairly confident of my conclusion as to the cause of the ‘ice event’, but conditions to
duplicate the event will not happen again until next winter.
2
Inspectors conclusions:
All clues indicate the cause of the ‘ice event’ is a faulty (broken and detached) dryer vent.
Why did the dryer vent break?
1. Lack of maintenance due to inaccessibility, and
2. Buildup of ice due to lack of maintenance
Here’s how this happens:
When the temperature outside is colder than the temperature inside, small quantities of warm moist (relatively) air exit the building due to the ‘stack’ effect. One location where this will occur is through the second floor clothes dryer duct/vent, due to it’s location high in the structure. Think of the second floor dryer vent ductwork as a little chimney.
As this trickle of warm air leaving the building, via the ‘little chimney’, reaches the cold surface of the vent flappers on the exterior wall, the moisture (water vapor) in the air will condense. If it is cold enough, the condensation will freeze. As more air passes, ice will continue to build until the hole allowing the air to pass is closed. So long as the little flappers are shut, the quantity of ice will be small, because it won’t take very much ice to freeze the flappers shut. Once the vent is frozen shut, the air will cease to flow out and the build-up of ice will stop.
Now, however, let’s say one or more of the little flappers is stuck open because of lint, particularly the upper flapper. The lint is there because you can’t easily get to the vent to clean it, and because the vent is clearly out of sight and out of mind. The build-up of ice would be quite significant. Inches of ice could build in an effort to close the 4” diameter hole as air continued to flow across the top of the ice. This much ice would be significant enough to break things due to expansion, or hold the duct frozen in place while the plastic vent expanded from warmth when the sun hit it. This much ice would be significant enough to pour considerable amounts water down the siding when the dryer was turned on and the warm air from the dryer melted the ice.
It must be assumed the dryer vent was not broken when it was installed, because contractors don’t build broken houses, so how did it break?
The only plausible explanation is contributing factors due to the build-up of ice.
If the dryer vent is repaired to it’s original design configuration, it must be assumed the same thing will happen again because:
1. It is still not in a readily accessible area to perform maintenance, and
2. It is still in a location that is very far out of sight and out of mind until something bad happens.
There is one other factor in the equation. Air pressure in the duct created due to a vent that is frozen shut. Pressure would certainly build, but I do not think the air pressure created by the dryer fan alone would be enough to ‘blow apart’ the dryer vent. However, the air pressure wouldn’t help the situation either, and it cannot be ruled out as a contributing factor."
At this point I didn't wanna pursue buying the house, how would I know that there are no issues with the attic? My insurance company will not pay for any mold issues as the house does not have a vapor barier, in this cause not caused by this, but I'm sure they will blame on it when it comes to pay out money.
I hope this gives you a better understanding of what's going on.
Thanks
Erik