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Part 1: Tests and Mockups Ensure Proper New Window Selection
By David Griffin and Ray Madore
December 2010 -
Windows & Exterior Walls
During a construction project, it's easy to lose sight of the details and focus on the big milestones — the foundations and steel erection, for example. But it's the little things that really determine the success or failure of a construction project. The foundation may be strong and the steel sturdy, but if the window systems are faulty, your building will leak — compromising the final outcome. The key to ensuring that the critically important aspects of window installation are not overlooked is to plan and implement a comprehensive and project-specific quality program.
As the term "quality" is used here, it has nothing to do with the level of finishes specified for the building. Instead, a quality finished product on a new construction project is a building that will perform the way it was intended to. Quality applies to the entire range of building components. So, for example, the plaster will not have cracks. Paint, carpet and tile colors will be consistent. No moisture exposure conditions will exist that result in mold. All the MEP systems will be working in concert with each other. And of course the windows won't leak.
Without a formal quality program, the chances of delivering on that promise are greatly reduced. That's why a program for testing window systems is essential to the overall success of your project.
A window system is part of the exterior wall system — it is made up of a wall, a window and a vent. Window systems are complex components of a building that require many different pieces in order to work properly. Much forethought and preparation is needed to pick the correct application.
The use of the window and the geographic region will dictate the criteria of the system. For example, if you're building hotels in a coastal climate, your window system will require different specifications than if you are building a school in the desert. A coastal climate requires windows with tight moisture protection, while a drier climate wouldn't need that. In addition, different building types have different demands for windows that open and close. The specification for a window system, including the vapor/air barriers and exterior wall, should take all the factors into consideration.
Windows are the weak link of the exterior wall system because they are open passageways from the inside of a building to the outside. If they are installed improperly or the specified materials will not work together to seal the building envelope, they will wreak havoc on the life of the building. In addition, windows are often an item that gets downgraded during preconstruction when an owner is trying to find ways to cut costs. As a result, it is essential to test windows to ensure that they will be installed with the best application for their specified materials.
With so many variables, it is very unlikely to have identical window systems on two different construction projects. There's a good chance the construction manager will be familiar with different elements of the window, but may not have installed them all together as a specific system. It is common for dissimilar materials — like wood and PVC — to be specified for a window system and it's the construction manager's job to determine how they go together to create the system.
The most effective and efficient way to test the window is to construct a functional mockup. This mockup can be constructed as part of the building or it can be free-standing, but it should contain all the components of the window and wall, including the air and vapor barriers, flashings, caulking, and the exterior finishes. Testing the mockup is critical when working with dissimilar materials.
It's important for the mockup to be built in the correct sequence by the subcontractor who will be performing the actual work on the job to ensure the mockup is built correctly and the same way it will be done on the building. In addition, the construction manager, architect, subcontractor, suppliers, owner and third-party consultants should all be a part of building and testing the mockup.
Because the long-term performance of the building is so important to the facility manager, you should understand and promote the importance of quality construction by taking an active role in drawing review, assembling the mockups, and the testing of mockups. In the end, though, the onus is on the construction manager to have a formal quality program in place and enforce quality standards among all subcontractors working onsite.
So how is a window tested? A third-party consultant should be hired to perform the investigation to ensure that an expert is executing the plan. Essentially, this consultant's job is to test the window system to the point of failure, using the kind of natural elements it will face in the real world — like extreme wind and water pressure from rain. This will detect the weak point in the window system. There are many different ways to test the window — air vapor testing, smoke testing and water testing among them. A consultant is typically hired to perform one of these various kinds of tests. If the window fails, it may be tested a different way to identify the specific weakness.
There are typically three ways a window system can fail in testing:
1. Product Compatibility. The materials specified for the window are not compatible with each other.
2. Product Sequencing. The sequence in which the materials are put together to create the window system is wrong and causes the window to fail.
3. The Window Itself. There are issues with the window from the manufacturer; this could be a missing or defective part or it could be that the testing in the field is more rigorous than the testing the manufacturer performed on the product.
The short- and long-term effects of the problems that are often found through testing could, if not remedied early, be disastrous for both the construction project and the building itself. In the short term, the construction schedule and budget would likely be severely affected by problems with a window system that are found late in the game. If a subcontractor installs half of the windows in a building and then discovers after a few days of rain that the windows leak, the firm has to stop working, investigate and find the problem, determine a solution, rip out all the existing windows, and start over. That could add weeks to a schedule, which most definitely would affect the bottom line of the project's budget.
If you get through the construction project without encountering a problem with windows, that doesn't necessarily mean that you're in the clear. If it turns out that materials in the window system are not compatible, they could peel away from each other over time and cause the window to leak years after the building was built. This will cause huge — and unnecessary — headaches, since you'll have to fix problems that would have been found by testing a mockup during construction.
Windows Product Showcase
Part 2: When Windows Fail
Part 3: Window Product Showcase