HVAC Question & Recommendation

[niceg3s]

We have a 1,400 sq ft house in Austin. There is a lot of dust being blown out the vents. It is not visible, but accumulates around the house. It doesn't seem to be affected by changing the filter. It is a 1950's house. The system was replaced in 2005, but the ducts are the original ducts from the 1950's. I am assuming the ducts are the issue. I had them cleaned, but that seemed pretty worthless. Will replacing them fix or help the issue? Is it possible to replace them without getting a new system? What sort of cost am I looking at? Anyone in Austin area that you would recommend?

Thanks.

[orlybow]

Lots of times just sealing around the air registers with caulk will take care of the dust problem. I would try that first before other more expensive remedies. Your hvac can cause a vacuum of sorts between your living space and attic space. This causes dust to be pulled in from your attic through the openings around the registers and any other attic openings. This is usually the most common cause...

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[bowhntrmatt]

There are several things that help this situation.

Duct replacement is a great idea, but there may be cheaper alternatives. If you do replace the ductwork, be sure the contractor does a pre and post test with a duct blaster to insure sealing and show you the improvement. In Austin there may be utility rebates available from duct replacement as well, depending on your provider.
For the next best thing, do a search for a company in your area that sells Aeroseal. It is an internal duct dealing process that works very well.
The cheapest way out is to do what the first response said. Go buy a case of caulk, take all your grills down and make sure there is no air gap between the duct and the Sheetrock. This also goes for all attic penetrations, like wires, fans, can lights, plumbing, etc.

If that old metal duct system is leaking a lot (and most do), it could be putting your house into a negative pressure and drawing in dust from everywhere.

[double bogey]

Also you need to look at your filter system. If you have a 1" filter, you need to upgrade to a high performance. I recommend an F100 Honeywell, or equal. Filters 10 times better, and you only need to change once or twice a year. The dust is most likely in your duct due to inadequate filtering.

As was mentioned earlier, if you have a leaky duct system, as it leaks, the pressure in the occupied space gets slightly lower, causing air to be pulled in where ever it can, bringing dust with it.
If your system is metal, and leaking, and dirty, it may be most economical to change it, and have it leak tested as mentioned earlier. Flex duct is pretty cheap.

[8mpg]

all the ducting needs to be mastic sealed at the connections... like the other said, seal around the registers to the drywall. Caulking works but they make a mastic tape that works wonders. You should do this for recessed lights as well. If you can, get a company to put in a whole home filter. its a 4-5" wide filter that goes up on the air handler. You change them 1-2 times per year but in the beginning you would probably change it every 3 months until you get some dust out.

While the a/c might be blowing the dust around, it coming into the house from other areas. Leaky windows, leaky doors, etc. Im sure a house in the 50s was a solid house but it was leaky as hell.

[niceg3s]

Thanks for the input. Sounds like I need have the ducts replaced and filter system. Also, need to use mastic and/or caulk on the registers.

[LWolken]

Seal around the outlet boxes in the ceiling with caulk, but also check the return air connections in the attic and make sure they are not pulling dust into the system from the attic. Its probably coming from blown in paper cellulose insulation.

[niceg3s]

Rats had chewed off a flex duct. Had a 6" hole sucking dust into the system. Rats are dead and hole is fixed.