What's Wrong With My Carpet?

Mystery Solved! Bill Garwood, home inspector extraordinaire, writes a weekly article for the AJC. I get this question a lot when I'm helping home-owners get ready to sell. Thanks for clearing this up, Bill!

Ask the Inspector: Ghosting? It’s a dirty problem, but don’t let it spook you
Air circulation is culprit of mysterious carpet-stains.

By Bill Garwood

For the Atlanta Journal-Constitution

Sunday, September 21, 2008

If you have light-colored carpets in your home, you may have experienced dark areas along the baseboards or even under doors. Perhaps you have noticed dark spots on your bathroom ceiling above the vanity lights. You may have even noticed that there appear to be dark streaks on your walls or ceilings.

Don’t panic, these stains do not mean you are a poor housekeeper, although eliminating them may require a lifestyle change.

The stains are known as ghosting. For ghosting to occur there must be a source of dirt or soot in the house. In many cases the dirt or soot simply enters the house from outside.

Since most houses experience some imbalance of pressures between the interior and exterior, a negative interior pressure will naturally draw dirt into the house through windows, doors or any other crack in the envelope of the house. Dirt and soot can also be created by the occupants of a house. Cigarette smoking, burning candles or incense, and the pilot lights on gas burning appliances all produce a certain amount of soot.

The most common area of ghosting is on light-colored carpets. In this case, an imbalance of pressures between the interior and exterior of the house results in an imperceptible airflow through walls. The air carries some of the dirt and soot with it.

When the air passes into or out of the bottom of a wall, the carpet acts like a filter and catches the dirt and soot resulting in the dark areas. Imbalances or even poor design of a heating and cooling system can result in air pressure differences between rooms and the areas outside them.

When this pressure imbalance occurs, air passes under the doors and is captured by the carpet. Streaking on walls typically occurs on exterior walls and is a result of a difference in temperature between the wall studs and the spaces between the studs.

In winter the wood studs will tend to be colder than the insulated spaces between them. This minor difference in temperature allows some imperceptible condensation of water vapor along the stud. This condensed water vapor traps the soot and dirt particles, leaving relatively dark, dirty streaks on the wall.

In bathroom ceilings the cause of ghosting is a little simpler. The heated air from the lights over the sink rises and carries the dirt and soot in the air with it. The dirt and soot collect on the ceiling above the lights.

Cleaning tips

Ghosting can be difficult to get rid of. It may require replacement of carpets and/or repainting of walls and ceilings. For less severe ghosting on carpets, a professional deep cleaning of the stains using an enzyme-based powder has been somewhat successful.

The following is a list of things that a homeowner can do to help minimize or eliminate ghosting:

• Eliminate or reduce tobacco smoking in your house.
• Eliminate or reduce candle burning in the house.
• Have pilot lights on furnaces, water heaters and gas logs properly adjusted by a licensed heating and cooling contractor.
• Replace your furnace filters regularly. Every couple of months is advisable.
• Clean and vacuum regularly using a crevice tool to clean around baseboards.
• Check your vacuum cleaner. If it is not clean, it may produce more dirt than it collects.
• Have your heating duct system professionally inspected to ensure against leaks.
• Undercut doors to allow passage of more air under them.
• Properly weather-strip doors between the house and the garage.
• Pull back carpets and caulk the gap between the floor and the baseboards.
• Consider installing darker carpets that will show the ghosting less.