Do you wonder why your house gets dusty so fast?

Do you have something like this in your attic?

Do you feel like your house is always dusty, in spite of how much you vacuum and clean? Have you tried all the tricks – HEPA vacuum cleaners, air cleaners, taking your shoes off before coming in the house, washing the dog…. all to no avail?

Chances are good that you’re being plagued by a leaky duct and air handling system.

When you have leaks in your ducts (virtually all duct are leaky) dust from the attic gets sucked into the ducts and distributed throughout the house. Even if you have an excellent filtration system on your air handler, the dust can be sucked in from places that don’t get filtered, and blown into your home, usually leaving fine gray dust everywhere.

Before you call in a heating/cooling (HVAC) contractor, there are a few steps that you can take yourself.

Warning: working in an attic can be dangerous. Many attics don’t have proper floors. Numerous people have taken bad steps and fallen through the ceiling, often resulting in serious injury or death.

Assuming you are comfortable working in the attic and can safely access the duct work and air handling system, here are some things to check:

  1. Ensure that the air filter port is sealed air-tight.
    At least  10% of the systems I see look like the one in this picture. The air filter port is open and an over-sized filter is sticking out the side. Not only does this rob you of 20%-50% of your system’s efficiency(!) and cause the air to get extremely dry in the winter, but it sucks nasty, dusty attic air into the system where it is blown throughout the house. Fix this simple problem  (get the right sized filter and tape over the port) and you will see immediate energy savings and probably a much less dusty home.
  2. the duct "boot" has a big gap

    Check your air registers around your house
    Your home’s air registers should mostly be clean. If some are much dustier than others, this is a sign of leaks near that particular register. Sometimes it will be a leaky duct leading to it, other times it may be the register itself is poorly attached to the ceiling, providing a gap right into the attic. I’m always suspicious when I see a really dusty register.

  3. On a cold and windy day, turn off your forced air system (air conditioner, heat pump or furnace) and see if you can feel a cold breeze coming from any of the air registers in the house. The duct system is supposed to be completely sealed, so you should never feel really cold air blowing in. You might feel cool air drifting in due to the ducts being cold, which causes the cool air to “drop” out of the ducts. But if you can correlate cold air blowing in with wind outside, you’re sure to have leaks. The more of a breeze you feel, the closer you are to the leak.
  4. Poorly attached duct

    Look around the attic to see if any ducts are visibly detached or “askew”, particularly at registers and ducts that failed test #3 above.
    These can be hard to find, but sometimes it’s pretty obvious. All the ducts should be nearly and strongly attached at both ends – where it leaves the main trunk lines and where it feeds the ceiling registers or air returns.
    I’ve seen cases where the ducts have totally fallen off and are just lying on in the insulation.
    Note: special tools and adhesives are used  to connect ducts in a permanent fashion. Do not attempt to repair these problems with “duct tape”! – this tape will fail and you’ll be left with leaky ducts again. Instead, industrial strength zip-ties and tensioning tools are used along with a sealant called “mastic.”

  5. Sometimes problems are hidden in walls
    You might not be able to find any problems in the attic but the problem could still lie in your ducts. Many duct systems run through walls and hidden cavities in your home. It is even common  practice to use naked wall cavities without ducts! Contractors will just pick a wall, ceiling or floor cavity and run air through it. This horrible practice really shouldn’t be permitted because it causes so many problems.
    This type of problem you probably can’t find yourself. A trained infrared thermographer (often an energy auditor or building scientist) may be able to locate the problem, but sometimes it can be very difficult.
  6. Beware of Vermiculite
    Some older homes have Vermiculite insulation in the attic. These homes should not be tested using a blower door or duct blaster and you should not poke around in this material because it may contain asbestos. Not all Vermiculite contains asbestos, but this is definitely a case of “better safe than sorry.”

I started this post saying that you shouldn’t call in your HVAC contractor and I’ll finish it by saying the same thing. Many HVAC contractors are not trained to find these leaks. Think about it – who created these leaky ducts in the first place?

As a building science / energy consultant, I’m biased because I’m an independent consultant, and I recommend that you use someone who is also independent to diagnose your issues. They might fix them as well or they recommend a high-quality HVAC contractor whom they know to do good work. They will also have special equipment like a “blower door” and a “duct blaster” that allows them to quantify the leakiness of your ducts much more quickly and accurately than someone without these tools. In fact, without at least a blower door, it will be very difficult to even find many duct leaks.

Fixing duct leaks can help make your house much less dusty and it has the side effect of making it more comfortable and energy efficient. This is one of those things that you’ll wish you had done years ago because it can make your house more enjoyable to live in every day of the year.


“Why does house get dusty when heat on and not with ac on?”

Occasionally, weird things happen. If you’ve gotten this far, you know that the dust is usually sucked in and distributed by the duct system. If that’s so, then how does the above situation occur?

There one possibility that comes to mind – moisture.

During the summer, the cold coils in the air conditioner are covered with water – this is the summer moisture getting drawn out of the air. When the dusty air moves through the coils, much of this dust could be trapped by that water. This would lead to much less dust when the air conditioner runs than when the heat is on.

“Does an energy audit show why there is so much dust in the house?”

Someone else asked this question. The answer is “maybe.”

If the energy audit is a comprehensive review of your home, done by a competent technician, then yes, the audit should be able to show why your home is dusty. To make sure, you should tell your auditor that you’re having a dust problem and you’d like some help finding out why. If they look confused and don’t suggest issues like the ones mentioned in this post, you should probably find a different auditor!

“Why is the air so dry in the winter?”

What does dry air have to do with a dusty house? Possibly everything!

If your duct system is sucking dusty air in from the attic, it will also suck in the very cold, dry air from the attic. When that dry air enters your house, it sucks up the moisture from your home like sponge, resulting in very dry air. That’s why an uncomfortably dry home in winter is a giveaway that the home is very leaky.

Keep in mind that the dry outside air could be coming from anywhere. If you have leaky windows and doors and a drafty house, it’s also going to be uncomfortably dry. That said, nothing dries out a house faster in winter than a leaky duct system that’s sucking in cold, dry outdoor air.

16 thoughts on “Do you wonder why your house gets dusty so fast?

  1. Will someone please explain to me the attic concept? I live in an apartment…the lower unit of a two unit building. My furnace is in the basement and the upper unit furnace is in the attic. People posted that attic insulation could be the source of dust from leaky ducts, but my ducts wouldnt reach the attic, correct? Would it be dirt and dust from the basement and wall cavities that is making my apartment dusty, and how do i fix that? It IS an older apartment and i have noticed a couple registers very scummy compared to others…so what does all that mean?

  2. I rent a one bedroom loft, I’m almost ashamed that I’ve waited over 2 years to be concerned about the amount of dust that I’ve been breathing, while doing deep cleaning I’ve find everything is saturated with thick dust, it’s coming from the combo washer dryer, I’ve consistently been cleaning, been having lots of trouble with my eyes being extremely dry, I think it’s from all the dust, I discover how it’s all over my hanging clothes, I though by just cleaning would solve it, but now I’m reading I believe something is leaking or not closed off right causing all this dust I’m breathing over 2 years now, once the landlord cam and did something replaced filters but it never went away, so now I’m gonna call him and get him out here to take care of this issue once and for all, I will not use the clothes dryer anymore untill this is solved. Anyone with advice I surely welcome

    1. How is the dryer vented? Does it dry clothes OK or does it take a long time? I think your idea of not using it for a while to see if that helps is good. If it’s still dusty when you aren’t using it then the problem is something else.

    1. I would look for a company that has RESNET certification, such as this one:

      There’s another energy auditor certification called BPI, but I’ve found RESNET to be more rigorous and the energy professionals are usually independent contractors whereas many of the BPI rated contractors are heating contractors too and that can lead to conflicts of interest. I’m not saying that it’s bad, just that RESNET is better.

      You can also contact your local building compliance office, where you get building permits, and ask them if they know of any independent energy professionals to help you with your problems.

      Here’s the RESNET website

      You can find local professionals on this page:

      good luck!

  3. Brand new duct work ran under house…….only one room gets dusty….the room where the intake is which gets extrmley dusty alonng with the walls etc close to the register and the room that has the register with the least air blowing out of it…….after reading your information would I be correct to surmise that the duct work to the register is loose…..not fitted right…..and therefore blowing in filthy air?
    Please help and your right don’t count on the ac guy! Clueless! Thank you so much for your help!

    1. It certainly sounds like leaky duct problems. If the feeds for those registers are accessible, they should be inspected.
      There are duct leakage tests that you can have done. If you contact an energy auditing company and ask about this, they should be able to do the test.

  4. I strongly suspect most of my dust comes from toilet paper, Kleenex and paper kitchen towels along with dust stired up when shaking and folding clothes. Also I think a greater level of humidity would help keep outdoor dust at bay and less wiill come into the house.

    I have a very large 3 room capacity Hepa filter placed between the kitchen and the living room and a custom “Air Sponge” furnace filter. My vacuum cleaner is equiped with a Hepa exhaust filter. I’ve placed filters inside of all the AC/heat registers.
    I live in a 730 sq. ft. upstirs apartment facing a beautiful wild green belt in Rocklin, California and have no pets. Allergies are not my problem. Dust just likes to cover everything and requires weekly removal. If I could just learn to love dust . . . .

    I often think about moving to the central Oregon Pacific Coast

  5. Am not an engineer but feel entitled to an opinion and also question.! I respect and disagree with my HVAC guy re source of grey dust bunnies on filter. He says it’s the dryer, I say attic insulation, which is off white/cream color is being drawn into system, changed by common dust to a consistent grey. I say if dryer dust, it would reflect color of clothes being dried. They’re generally NOT grey in color!!

    1. Unless you’re venting your dryer into the house, I don’t see how it could be dryer dust. That simply doesn’t make sense to me. But perhaps he knows something he hasn’t told you, like the dryer duct is leaking into the house? Has he explained how the dryer lint which is going outside is working its way into your house to be sucked back into the HVAC filter?
      One thing to remember is the dust collected by the filter is almost always gray since it’s a collection of all the different colored hair, skin, clothes dust etc. So it can be quite difficult to determine the exact cause of the dirty filter without more detailed analysis.

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