How Hidden Problems Can Shorten Window Life
By James Piper - August 2007 - Windows & Exterior Walls
The owner of one high-rise building found out the hard way what can happen when windows are ignored.
The windows — aluminum, dual-glazed units — were only 20 years old, but during that time the only maintenance performed was caulking when occupants reported leaks. In the meantime, gaskets between the glazing and the frames had deteriorated, allowing water to penetrate into the frames and the space between the frames and the building’s exterior wall. The moisture accelerated the corrosion of frame fasteners and gradually many of them came loose.
The building owner knew nothing about the problem until a severe storm blew through the area. High winds caused fasteners to fail and windows were blown either into or out of the building. Fortunately, no one was injured.
The damage to the building’s interior was relatively minor, but damage to the windows was another story. The building owner had to replace all of the building’s windows. The price tag for the work: $4.5 million. With regular inspections and maintenance, the failed gaskets would have been detected and corrected before the damage occurred. The existing windows could have lasted another 20 to 30 years.
No matter what facility executives might hear about “maintenance-free windows,” the reality is that there’s no such thing. While maintenance requirements will vary, they will always exist.
Part of the reason they exist is that windows are a long-life item. Most types can be expected to have a service life of 30 years or more.
While a long service life helps make the investment in a high quality window worthwhile, it can also work against facility executives when it comes to maintaining them. Long service lives mean that deterioration takes place slowly and often goes unnoticed until too late.
Long service lives can also give facility executives a false sense of security. Too many people believe a component rated to last a long time does not need regular maintenance.
For windows, this belief can be disastrous. When problems develop in window systems, they most likely will be very expensive to correct. If windows have been allowed to deteriorate long enough, replacement — an expensive and disruptive project — may be the only option. A good ongoing maintenance program can postpone the need for replacement while maintaining the performance of the windows, all at a fraction of the cost of replacement.
What Goes Wrong
Why do windows need regular maintenance? Consider the environment in which windows function. They are subject to extreme temperature differences — as much as 75 degrees F or more. The weather may be extremely dry for part of the year, then wet and humid. Windows must withstand high winds and exposure to ultraviolet light. If operable, they must withstand regular openings and closings without excessive wear and tear.
These environmental conditions take their toll on windows: finishes fail, sealants lose flexibility, components rot or corrode, insects bore into wood and movable parts deflect or corrode. Unfortunately, the damage is cumulative and eventually replacement becomes the only economical option.
By far the most common problem that arises from inadequate maintenance is moisture damage. Plugged or inadequate weep holes over window openings can allow moisture to get into components and interior spaces. In operable windows, the weatherstripping between the sash and the frame can harden, shrink or fall out, creating a gap that allows water in. In fixed windows, the gasket between the window glazing and the frame can shrink, harden or split.
In both operable and fixed windows, the caulking or sealant between the window frame and the exterior wall can crack or fail, allowing water to permeate window components, the interior portion of the wall and the building interior. Wood windows are particularly vulnerable. Even things as simple as cracked, loose or missing sections of glazing putty will allow moisture to saturate wood components, hastening deterioration.
Such failures also allow air to leak in, significantly changing the thermal properties of the window. If there is enough air infiltration, it can produce condensation on the glazing, frame, or surrounding surfaces.
Harsh environmental conditions also take a toll on the exterior surfaces of windows. Paint can crack, peel or flake, allowing moisture to permeate the exterior components. With aluminum windows, the anodized finish on the aluminum can fade or bleed onto the surrounding surfaces. Even vinyl windows can suffer from chalking and fading as a result of environmental factors.
Moisture, combined with wear from routine use, also takes its toll on window hardware. Operators become corroded and difficult to move. Casement hinges corrode and can lock in place or stick. Locks can be difficult or impossible to secure as a result of wear and misalignment. Other hardware can corrode and fail.
Clearly, the best way to maximize window life while minimizing problems is a program of regular inspections and routine maintenance. Ideally, every window in a facility should be inspected annually. However, this may be impractical in facilities with large areas of glass. If that’s the case, an alternative is to inspect a representative sample of the windows, usually between 15 and 20 percent of the total, and project the findings to rate the condition of all windows. Make certain the sample includes all types of windows installed and all exposures.
All inspections must be tailored to the type of window. Different kinds of windows have different symptoms, but there are some common problems to look for.
Start by examining the condition of the interior surfaces around the window. Look for water stains, rot and other indications that moisture has been reaching the interior. Make note of where those stains are so that maintenance crews know where to look for the source of water. Photographs will help document the findings.
Check the fit of windows. Frames and sashes are subject to changes in size with use and exposure to temperature cycles. As a result, a gap can form between window components, increasing both air and water infiltration. Check the fit of all window components, making note of any that are excessive.
Operable windows should be opened all the way then closed completely to see how easy they are to operate. For wood windows, any binding in operation could signify swelling or warping of the window frame or sash — both indications that moisture is penetrating some components. In both metal and wood windows, failed or corroded operators can cause problems operating the units.
Examine the caulking between the frame and the building wall. Many window designs use a flexible seal between components. With time and exposure to ultraviolet light, moisture, and temperature extremes, the seals can lose flexibility and fail. Examine all seals over their entire length for proper fit and sealing.
Inspect the finish on the exterior of the window for defects. In most cases, paint failures on wood windows can be traced back to moisture. Identify areas not only where the paint has failed but also where it is likely moisture is getting into the wood. Paint failure on metal windows can accelerate the deterioration of the window’s metal parts. Identify not only where the paint has failed, but also the cause, if possible.
For wood windows, check all surfaces for rot and decay using a metal probe. Identify all areas where rot is detected. Note the most likely areas where moisture is gaining access to wood that shows signs of rot and decay.
Repair or Replace
There are three general categories of window repairs: routine maintenance, parts replacement and structural repairs. If the windows are new or if a maintenance program has been in place for some time, chances are most of the identified defects can be corrected through routine maintenance or parts replacement. In older facilities, particularly where no maintenance program has been in effect, chances are some structural repairs will be required. When the number of windows requiring structural repairs becomes large, typically more than 15 or 20 percent of the total, facility executives may want to consider replacement. For these situations, money that would be used for repairs may be better spent on new windows.
Typical routine maintenance and parts replacement tasks include painting, caulking between the frame and the building wall, adjusting window operators, and replacing damaged gaskets and broken or fogged glass. It is important that staff performing routine maintenance activities understand what is needed to make the proper repairs. Too often maintenance personnel try to fix window problems using sealants without first identifying the cause of the problem. In these cases, they often move the problem from one location to another or simply make it worse.
If the window is operable, all moving parts should be lubricated with the proper lubricant, and the mechanism cycled a number of times.
If windows are expected to last, they can’t be ignored. If they are, the results can be expensive, even dangerous. A diligent maintenance program more than pays for itself.
James Piper, PhD, PE, is a writer and consultant who has more than 25 years of experience in facilities management. He is a contributing editor for Building Operating Management.