1. They're drafty. Drafty windows is an issue that occurs when there are deficiencies in the weather stripping between the moving parts. It is a problem because air leaks will cause the efficiency of the window to drastically reduce and will cost you more to heat or cool the living space. To solve this problem, the weather stripping should be replaced with new material. This can be done by a qualified window contractor, or in some cases it can be done by the homeowner. The material needed is available at most home improvement retailers.
2. They stick. Sometimes you will find that when you try to operate a window, it sticks in the closed or open position. This could be a problem. If it is stuck open, it will allow wind and rain to enter the home causing damage. If it is stuck closed, it could be an egress problem in case of fire or other emergencies.
This problem can be caused by dirt or debris in the tracks or carelessly painting the moving parts together. Scheduled cleaning and lubrication of the tracks is recommended. I have found that spray furniture polish works well. It does not attract dust and will not damage plastic parts that some oil based lubricants will. Do not use oil based lubricants on vinyl windows!
3. They contain lead paint. Some older windows may have been finished with a lead based paint. It has been determined that the inhalation or digestion of lead paint particles can be a health hazard. It is recommended to paint over the lead based paint with an oil based enamel. Be very careful when prepping the surface. It is when the lead paint particles are airborne that they are dangerous. ALWAYS reference the EPA's Renovation, Repair and Painting Requirements when working with any lead paint or hiring a contractor to do so. Please be aware that according to the EPA rule, anyone you hire to perform this work must be certified by the EPA and trained to follow lead-safe work practices.
4. They won’t stay open. Single or double hung windows that have defective sash cords are a personal injury waiting to happen (especially to children) because when the lower portion of the window is raised, it is expected that the window will stay open. But with defective sash cords, this is not so and the window will fall, possibly catching someone's fingers. This is a common problem that is caused by the balance system for the sash not functioning properly. This could be from broken cords to dirt and debris hindering the operation. This condition could not only cause injury but damage the frame or glass in the sash as well. A qualified window contractor should be able to repair or replace the balance systems for proper operation.
If you are a more advanced do it yourselfer and don't want to tear apart the sash, you can research supplemental springs like this one that fit into the jamb and hold the window open by pressure. One at each side of the sash will do the trick.
5. Weep holes are covered. This is a condition when the designed weep system of the product is blocked preventing the expulsion of rain and moisture from the product. This can be caused by faulty construction, insect webs or other debris. This problem can cause water to enter the inside of the living space causing damage or the possibility of mold or fungus. It can be cured by periodically checking and cleaning out the weep holes as needed.
6. They have water leaks and/or rot. Some wood window products without the benefit of cladding can become warped or sustain rot damage causing leaks at the sill. These leaks can cause damage to the interior of the dwelling as well as the possibility of mold forming inside. A qualified window contractor can repair or replace the needed parts to cure the situation. On many products the whole window may need to be replaced. This issue should be addressed right away.
7.They have broken muntins. Broken muntins, sometimes called grids, is a condition in many insulated glass panels. Internal muntins, those in between the glass insulated panels, can get displaced for various reasons. This is an aesthetic problem that will not cause a panel or structural failure of any kind. To repair, the complete insulated panel will need to be replaced by a qualified contractor.
8. They sweat, fog, or have condensation or moisture where they shouldn't. This is normally not a significant energy loss but is or will become an eyesore as time goes by. Windows are manufactured with the air evacuated from between the dual panes of glass which are then sealed. Overtime, the seals can fail, allowing air to get in between the panes. When the temperature differential from the outside to the inside is just right, the air moisture will condense inside the panes. When the moisture evaporates, it leaves behind the impurities (minerals / alkali that were in the water) creating an unsightly film. This can be caused by age of the panel, severe exposure to direct sunlight, or continual landscape sprinkler spraying of the panel. In a storm window application, this can be repaired by sealing the edge and frame where the storm window attaches to the main window. A sealed insulated panel will need to be replaced by a qualified contractor. Please note that new technology in sealants will make newer insulated panels last much longer than in the past.
Also sometimes, on cold winter mornings, there is a small amount of moisture on the bottom of the interior glass surfaces of windows. This is caused by excessive moisture inside the house condensing against the cold windows. Usually, the humidifier is turned up too high, or a bathroom exhaust fan is not properly removing the moisture created by the morning shower.
9. They have failed or missing sealant. Sealant (caulk) has a tendency to deteriorate over a period of time. It will shrink and cause gaps to let the outside elements enter the structure. This problem causes drafty windows and could cause a water intrusion hazard. Resealing is an easy affordable repair that can be done by most homeowners. It is a good idea to remove the old sealant with a razor knife. Then using a caulking gun and a quality sealant, run a bead to fill the void left by the removal of the old product. It really looks good when you wet your finger and run it over the bead to smooth the surface. If you do take on this project, please be aware of ladder safety and fall protection.
10. They're dirty! Windows should be cleaned at least a couple times a year, but it's probably the least popular of all home maintenance tasks (maybe tied with cleaning the gutters). But an article on This Old House.com claims to have the answer to our problems! The issue, TOH explains is that homeowners insist on cleaning windows with wadded-up paper towels, spray cleaner, and a ton of elbow grease. "All that rubbing isn't a good idea," says Brent Weingard, owner of Expert Window Cleaners in New York City. "You're just moving dirt around from one spot to another and putting a static charge on the glass, which attracts more dust and dirt. The article goes on to give us the secret to success with step by step instructions. Check out the full article here. But don't go overboard! Did you know that excessive cleaning may cause some glass coatings to wear off? Always follow the manufacturer's cleaning instructions.