High-Performance Buildings - Register now >

4  FM quick reads on Windows

1. Regular inspection lengthens windows' lifespan

Today's tip is to inspect windows regularly. 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, without regular window maintenance the damage becomes cumulative and eventually replacement becomes the only economical option.

Ideally, every window should be inspected annually. However, this may be impractical in facilities with large areas of glass. If that's the case, inspect a representative sample, usually between 15 and 20 percent of the total. Make certain the sample includes all types of windows installed and all exposures.

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. Photographs will help document the findings.

Frames and sashes may change 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.

Operable windows should be opened all the way then closed. For wood windows, any binding in operation could signify swelling or warping— both indications that moisture is penetrating some components.

Examine the caulking between the frame and the building wall. Many window designs use a flexible seal between components. With time and wear, the seals can lose flexibility and fail.

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. 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.

2.  Daylighting can reduce energy bills, improve satisfaction

Today's tip is to learn more about daylighting as a possible lighting strategy - but a well-thought-out daylighting plan requires more than just windows and skylights.

Along with minimizing artificial light and reducing electricity costs, daylighting can lower HVAC costs. Electric lights produce a lot of heat, but if properly controlled, natural lighting generates hardly any heat at all.

For most buildings, daylighting energy savings range from 15 to 40 percent. It can also improve the productivity and satisfaction of employees, students and even clients and retail customers, since people have a natural attraction and need for daylight. Even retail stores like Wal-Mart have seen the benefits of daylighting for both employees and consumers. In an experiment, stores that included skylights over certain departments found that overall sales per square foot were higher in the departments lit by natural light.

A high-performance daylighting system may initially require a significant investment. However, if the project team uses an integrated, strategic design approach, a company's overall long-term savings make up for it.

One important point is controlling glare. Direct sunlight penetration in classrooms and office spaces often produces an unpleasant glare on work surfaces, making it difficult to view a computer screen. Properly oriented windows and skylights can admit direct and diffused daylight, producing light while also reducing glare. The selection and placement of windows and skylights should be based upon climate and the design of the building.

Daylighting also must control the amount of heat that enters a building. Window treatments, window films and glazing can shade a window or diffuse direct sunlight. This can reduce overall cooling loads, eliminating the need for a larger cooling system, resulting in additional overall savings.

Some architectural features, such as a building's roof, atrium shapes or a building's angles, can prevent daylight from illuminating a space. To prevent daylight obstruction, wall openings should be strategically placed within the space. For example, if elements that can block daylight are located high up, they should be as far from wall openings as possible. In a plan that features both open and enclosed spaces, open space areas should be close to the wall openings. This maximizes the effect of daylight, reflecting light deeper into the space.

3.  Solar Window Film May Reduce Cooling Load

Today's tip is to consider solar window film for greater energy efficiency. Solar heat gain through windows is responsible for roughly one-third of a building's cooling load, according to the Department of Energy. That makes applying solar window film a logical step in reducing solar heat gain and improving the energy efficiency of a building.

Solar window film is applied to the inside of a window, where it reflects and absorbs heat from sunlight, thus reducing heat gain. Near-infrared radiation makes up 53 percent of the solar spectrum, visible light 44 percent, and ultraviolet 3 percent. When rays from the sun hit a window, some of the energy is absorbed and some is reflected by the window, but most is transmitted through the glass.

A pane of clear glass reflects about 6 percent of solar radiation, absorbs 5 percent, and transmits the remainder. Installing solar control window film increases the amount of solar energy both reflected and absorbed by the window. Most films have a thin metallic coating, made up of aluminum, stainless steel, silver or a combination that reflects and absorbs solar radiation. The most important performance measurement of window film is the solar heat gain coefficient (SHGC), says Darrell Smith, executive director of the International Window Film Association. SHGC measures the total amount of solar energy transmitted into the room. The heat rejection of window film can be as high as 80 percent, says Smith.

A reduction in solar heat gain can translate directly into fewer kwh used for cooling. What's more, by reducing the amount of cooling needed during peak periods, demand charges can also be reduced. Some utilities offer rebates and other incentives for installation of window film because of its ability to help save energy.

4.  How To Decide Whether To Replace Windows

Today's tip is considerations to keep in mind when you're trying to decide if it might be time to replace your facilities' windows. Window replacement projects can be expensive and time-consuming, so facility managers will want to consider these five questions to help guide their decision:

1. Is the existing window system structurally adequate and does it accommodate building movements and structural loadings? If not, it's probably time for a replacement. This is critical from a safety as well as a performance standpoint.
2. Is the system effective at controlling water leakage, moisture migration, or unwanted air infiltration?
3. What is the condition of the system components? Check the frame, sash, glazing, hardware, weather stripping, sealants, and exterior paint or other surface coatings.
4. Is it possible that the adjacent wall system is contributing to the problems experienced? If that's the case, it may be time to do some wall renovation instead of replacing the windows.
5. Is the building historically significant? If so, there may be a few more hoops to jump through in selecting particular window products.

In general, if the following conditions exist, replacement is probably preferable to repair. One: Is there excessive deterioration of the window system? Two: Is the effectiveness of the repairs questionable? Three: Would the cost of repairs approach the cost of replacement, or does the life-cycle cost of replacement prove cost-effective based on lower energy and maintenance costs. Four: Is it impossible to do ongoing maintenance practically after repairs are made?

Deciding to replace windows isn't any easy decision, but making the right decision based on careful assessment of existing conditions can help save money in the long run.


Windows , inspection , maintenance , sealants , moisture , rot

High-Performance Buildings - Register Today!

QUICK Sign-up - Membership Includes:

New Content and Magazine Article Updates
Educational Webcast Alerts
Building Products/Technology Notices
Complete Library of Reports, Webcasts, Salary and Exclusive Member Content

All fields are required.

click here for more member info.