Comment by Judi Lyall

Good morning,

   I have a client that complained that certain rooms were either cold or hot. She had 45% leakage. We gave her more air, tightened the ducts and now she called and said that the home is now getting very dusty. What is the cause and what to do next. It has gone through the summer with the air blowing thru it, I would think the the dust in the ducts are already blown out

thanks for your reply

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Morning Judi, as I mentioned on the comment wall I have a few thoughts on this;

While sealing up the duct leakage can help improve air flow to rooms that might be to hot or cold, I generally find that is not the main issue or is just a part of a bigger issue. Mostly when looking at these issues one also has to check for poor design issues. (same size trunk running the entire length of the house / improperly sized registers & returns / dampers not installed or used)

In some cases, sealing up the unit & maybe playing with the registers / dampers can help with the original problem and maybe more than adequate, but in others you can be looking at an issue with increased static pressure resulting in parts being overworked & burning out, the unit freezing up, etc... (hint, hint always check the static pressure - that one test is basically just as important or more important as testing the leakage)

Getting back to the increased dustiness of the house, you may have a leak in the return system just after the filter which is pulling in dirtier air & redistributing it (you might want to check the coil) /// you may still have a lot of leaks on the supply side sending that air outdoors & requiring the system to pull makeup air in from the attic, walls, etc...

Hopefully some of the HVAC pros will stop in as this really is my weak section, & maybe a few others with some other ideas (as I stated earlier, there are many other reasons for this issue)

I agree with Sean.  I'd test the entire distribution system again for leakiness, and then test return leakage and then supply leakage.  And, I'd check the pressure in each room with reference to the rest of the house or the outdoors to help figure where the dust is being sucked from.

Pressure Relationships within in a home are weird.  Change something, and something else changes.

Did you do a BD test originally and then after duct sealing?  Have you done one since?  How are those numbers changing? Are you anywhere close to 3 ACH at 50?  If the house seems more dusty, is the stuff coming from outside instead of the ducts?

Where are the ducts located?  Attic, crawl, conditioned space, multiple locations?  Any panned body cavities?  You did some air sealing, but where did the sealing not occur?  Did you achieve the duct leakage goal?  How much more can you achieve?

A couple years ago a client called with a "dusty house" issue.  After going over everything I could think of, the lady said, "It's dusty even right after I run the vacuum."  Then the "light in my head" went on; check the vacuum.  Sure enough there was a hole worn in the cloth filter bag.  I have had another client with a similar issue as well, but couldn't check the vacuum since she used a cleaning service.  So, there is a possibility that it's not the HVAC at all.  This is a fun business!

You have to identify the source of the dust.  The dust may be coming in from the ducts or somewhere else.  Like John already asked, did you do pre and post BD tests?  Keep looking - if it's there it's getting in somewhere.  You should have to find out where.

What is the before and after Duct Leakage to Outside and Total Duct leakage? What about the blower door #'s? It sounds like you may have missed some substantial duct leakage or other air sealing when completing the workscope. What other installations were part of the workscope? If you dense packed walls and they are using panned cavities for ducts in parts of the house, there could be cellulose that was introduced to the duct system. If you have a dominant return duct leak in a dusty area that would likely introduce dust to the distribution air. The same would hold true if you had a dominant suply leak in an attic area. These are just a couple of examples of what may be occuring.

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