Posted by: SherlockHomesSY | 28 Dec 2010

Common Complaints: Dust from Strange Places

Dryer LintDUST! Part 2 of 2: Strange Places

Typical causes
– Shell Duct Leakage
– Duct Leakage
– Tight Walls & Unsealed Ceiling
– Ventilation systems
– Hot Attics
– Clogged Dryer Ducts

Dust is almost always the result of air leakage, either through the shell (walls, floors, and ceilings) or ductwork.

Two blog posts are needed to discuss this common complaint.  In the last post, we looked at it from how it gets in from outside.  This second post talks about dust coming in from strange places.

What is Dust? It’s a bunch of stuff: pollen, dirt, mold, lint, and insulation – just to name a few.  Let’s not forget drywall, flour, sawdust and other things.

The usual place for dust to get inside house is from outdoors, through air leaks and duct leaks.  No one really expects a lot of dust from three other familiar places: ventilation, hot attics, and clothes dryers.

Ventilation Systems. There are two types of ventilation systems considered here: spot and fresh air.  Both cause their own problems.

Spot ventilation is used in bathrooms and over cooktops to get rid of moisture and grease.  They also have the advantage of getting rid of odors and other gases.  They powerfully pull air out of the house and blast it outside.  The vacuum created in the house, pulls air from where?  You guessed it: the shell.

Whole house fresh-air ventilation to the rescue?  It depends.  We’re not talking about whole-house fans.  If you use them, expect to dust early and often.

If you use anything that sucks air out of the house (exhaust only ventilation), dirty outdoor air is pulled inside.  It’s best to have a good air filter in the heating and cooling system—that runs year round—to capture the dust.  The alternative is to draw outdoor air in for fresh air (supply only ventilation).  It’s possible to clean the air before letting it in the house.  For either of these ways to work, the house needs to be relatively tight by air sealing and duct sealing.

Hot Attic. Another condition causing a lot of dust is attics with steep roof pitches.  Somebody forget to tell the builder that ventilation rules that work for houses with pitches less than 6 inches per foot (< 6/12) don’t work!  Somebody, in their infinite wisdom, decided the best way to solve the hot attic problem is with a power ventilated roof fan.  This giant behemoth odoes an awesome job of pulling air.  It doesn’t get enough from the soffit vents, so it yanks conditioned are right out of the house.  Oh yeah, that makeup air comes through holes in the floors, walls, and ceilings.  Here comes the dust!

Even without the fan, the air draw from the attic is strong.  When the air get hotter, it rises faster—pulling outside air in with greater force.

The solution here is to either insulate the roofline or better ventilate the attic.

Clogged Dryer Ducts. An unusual and unsuspected source of dust I’ve ran into in my own home is the dryer duct.  In this house, the duct went straight up, through the roof.  I didn’t even know they put dryer ducts up there!  The house was built in 1962.  Early in this decade, I discovered I had dust bunnies everywhere.  When I looked into the dryer duct, I found a 4” duct had a 1” layer of lint all around the pipe, leaving a 2” hole.

I’m not a fan of dryer ducts through the roof because they are a fire hazard.  The moral of this story is to clean the dryer ducts often.  I use the same methods chimney sweeps use to clean chimney flues.

Resources

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In Conclusion

All that dust is making me choke, so I’m having a hard time breathing!  Next, we’ll look into breathing difficulties!

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