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Cure for dirty soffits?

Jay

Jay

SAWHORSE
Joined
Apr 8, 2018
Messages
87
Location
NJ, USA
Hello all, I have a client with vented soffits which continue to get very dirty in the few years since the home was built. Thought I would share pics and perhaps get some feedback on the cause of this. What is odd is that it only happens with this house, not the neighbors or any other home in the area. Hoping there is some scientific explanation that I am not considering. many thanks!
 

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More negative pressure in vented attic space. Possibly more bypass. I'd look for gaps in thermal barrier at ceiling.
 
It appears to be dust and pollution built up as outside air is pulled in. Is there an attic exhaust fan? Passive convection should not cause this as it lacks enough force to move lots of air.

But hey now what do I know? Perhaps a larger lower vent opening would relieve the tendency to pull so much through the soffit.

Perhaps there is no attic and some other action is sucking air through the soffit. It looks like the upper soffit is clean and that may be because it's not vented or .....well who knows?
 
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I would suggest that the home owner also check to see if there are any exhaust vents terminating within the attic. The moisture from a bathroom vent or kitchen exhaust duct attracts dust and can promote surface molds.
 
Soffit vents are where the air is drawn into the attic and will exhaust through ridge vents, gable vents, turbine vents, etc., that are located higher than the soffit vents.

Does this occur at all soffit vents around the house, or just on one side? Are there kitchen, dryer, or bathroom exhaust vents located below?

Kitchen, dryer, and bathroom vents may include moisture and grease that could cause dirt to collect.
 
Thanks for the info! The building thermal envelope is closed cell spray foam. Attic is mostly conditioned space as a habitable half story. The vented soffits are only active passively for the small attic spaces at the roof skirts. I need to get back over there and do some thorough investigation regarding other factors mentioned that could be affecting the situation. Will report back with my findings. Thanks again,
 
I think you said the soffit vents don't connect to ridge vents or similar. I'd guess the bouyant warm interior air is being forced out these soffit vents. It's cold and moisture condenses and dirt sticks. Lots of dirt in interior air - just look at insulation in an attic floor above an interior partition. Often black.
 
bill1952 said:
I think you said the soffit vents don't connect to ridge vents or similar. I'd guess the bouyant warm interior air is being forced out these soffit vents. It's cold and moisture condenses and dirt sticks. Lots of dirt in interior air - just look at insulation in an attic floor above an interior partition. Often black.
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@bill1952, I think you are probably right, especially if this occurs at all soffit vents.
 
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