Buildings

Dust Problems

Q: My wife and I live in a single-story house built in 1972 with a full, unfinished basement and a gas-fired hot air heating system. There are uninsulated ducts in the basement, blown-in insulation, which I think is cellulose, in the attic, single-pane aluminum windows, three kids, and one dog. Our problem is that there is dust everywhere! I suspect the attic insulation, but I don't know for sure. Is there a way to reduce the dust in our house?

A: The obvious answer is to simply get rid of the dog. Just kidding! Persistent dust is not only annoying, but can also be a health hazard. Not to mention the snide comments about your poor house-keeping made by in-laws, neighbors, and the washing machine repair guy.

The causes of dust in a house are often difficult to track down, since there are so many possibilities. Sitting here at my computer, there's no way I can tell for sure whether the attic insulation is the source.

Twenty-six-year-old attics tend to be pretty dusty, regardless of what type of insulation they have. Some types of cellulose, particularly from that period, do seem to be "dustier" than most products on the market today. So let's assume your hunch is correct, and the source of the dust is the attic.

In order for this to be true, there has to be a pathway for the dust to get from the attic into the rest of the house, and there must be some driving force to move it. The most likely scenario would be leaky return ducts in the attic sucking in the dust and moving it throughout the house via the heating system, except that your ducts are in the basement.

The next thing to look for, then, are holes between the attic and the living space. Often there are large holes, such as the unsealed tops of plumbing chaseways, dropped ceilings above closets or kitchen cabinets, attic access hatches that don't seal well, around and over recessed light fixtures, around chimneys, big gaps around plumbing, etc. There are also smaller holes and gaps between the drywall and the top plate of the walls, around wiring penetrations, etc.

All of these holes and gaps are potential pathways for dust to be sucked into the house from the attic. If there are holes, the next question is, "What is the force that would cause the house to suck?" In your house, the most likely force would be negative pressures caused by leaks or imbalances in the forced air system. If, for instance, the supply ducts in the basement are very leaky, then the system is blowing less air into the living space than is coming back through the return ducts. This will cause the house to have a negative pressure relative to the outside (and the attic). In other words, it will cause the house to suck air out of the attic, if there are holes.

In some houses, this same effect is created by closing bedroom doors. The heating/air conditioning system is blowing air into the bedrooms, but the air can't get back out to the return duct located in a central hallway. The bedrooms are being blown up (like a balloon, except the sheetrock doesn't stretch) and rest of the house is under a negative pressure, with the return trying to suck in air from wherever it can get it.

If the easiest place for that air to come from is the attic, then that's where it will come from, complete with dust, squirrel droppings, insulation fibers, tiny pieces of Christmas tinsel, and whatever else might be in the air path between the house and the attic.

Of course, it's also quite possible that these same forces are sucking air into the house from the basement or from outside, rather than from the attic. The only way to know for sure is to have the house tested with a blower door, a device designed to locate the holes in the house and measure their size. Find a contractor who also has a duct tester to measure how leaky the ducts are.

Such a test will be a good investment. Aside from the dust, the air is probably also hot and wet in the summer, cold and dry in the winter, and contaminated with a variety of pollutants all year round. Identifying the problems and fixing them will not only improve your dust situation, but will also reduce your energy bills, increase your comfort, and enhance the health of you and your family. And even the dog.