IGU’s, Windows and Glass
Windows are essentially glass panels, usually operable. They are placed in the exterior walls to allow views and provide ventilation and light. Permanently build into the framing, windows are an important and fundamental part of the infrastructure of your home. Windows are also critical escape routes from bedrooms in the event of fire or other emergency. Because of that, building codes require that windows in those areas conform to certain sizes and configurations to allow human passage or “egress”.
Mankind’s use of manufactured glass has a long history going back maybe 6000 years. The earliest windows were made from small pieces of this early glass held together to create a large enough panel to be useable and allow light in. This technique continues to this day in the form of leaded, or stained-glass windows and the best examples are made by highly skilled artists.
Flat, or plate glass that we are familiar with today was only available in very small batches from the first makers as early as the middle 1800’s. Mass production of glass did not occur till the Ford Motor Company invented “continuous ribbon” production in the 1920’s.
Glass can now be manufactured in just about any size and configuration that is transportable. The Hubble Space Telescope, any of the Apple computer stores and the Grand Canyon “Skybridge” are good examples of extreme engineering with glass.
There are many different types and styles of windows but the basic residential configurations include: fixed panel (non-moveable), sliding (opens by sliding sideways in a track), double-hung (these are stacked windows that both open by sliding up or down vertically), single hung (stacked pairs of windows where only one is moveable) casement (these crank, or push open and are hinged from one side or the other) and awning (these crank, or push open and are hinged from the top). If I missed some, kindly let me know and I will add them to this list later.
Up until the 1960’s all windows consisted of a single pane (layer) of glass. These let light in and blocked the wind OK but provided very little in the way of thermal insulation value. To make up for that, some homes in cold climates were cleverly fitted with removable storm windows that provided a second layer of thermal protection. In summer, the storm window could be removed and replaced with a screen. This was both time consuming and inconvenient because screens or storm windows had to be handled, stored and protected from damage when not in use. Nevertheless, they effectively served the purpose of adding an insulation layer when needed.
Insulated Glass Units
As energy conservation became more important, building codes were enacted that required window designs to be more energy efficient. One solution was to make window panels using two panes of glass with a sealed air space sandwiched in between. The trapped air formed a thermal break much like the early storm windows. These were the first insulated glass units or IGU’s. Early insulated glass units were plagued with failures of the air seal between the two sheets of glass. Failures cause the windows to “fog” up unattractively as shown in the photo below. Fortunately, technology has caught up and IGU’s are now considered reliable. They are currently the norm for nearly every glass window in the US.Insulated windows eliminated (or at least greatly reduced) condensation on the glass during cold weather. It was then discovered that on very cold days a new problem of condensation would occur on the metal (steel or aluminum) window frames. This was annoying because enough water would be produced to stain and ruin any window trim finishes. The solution was to provide an insulated frame which is what we have on almost all windows today.
Thermal-Break Frames and More
Modern windows can now be had with insulated or thermal-break frames of wood, aluminum, steel, vinyl or fiberglass in nearly any shape. The glass units or IGUs can be ordered in various thermal configurations as well as with special optical coatings to reduce damaging UV rays. They can also be ordered with integrated blinds sandwiched between the glass panels.
Hawaiian and other tropical area resorts began using sliding or moveable window walls years ago. These allowed entire “wall” areas to be opened up from floor to ceiling to the outdoors. In good weather, the occupants could enjoy the outdoors while sitting at the dining room table or lounging on a couch in the living room. In bad weather, the glass wall would slide closed and the view was never interrupted.
Architects soon began using window walls in residential applications and by 2017 they were very much on the “must-have” list for most custom home considerations. When incorporated well into the overall design, nothing takes advantage of a gorgeous view better than a disappearing wall of windows. To work and look best, window wall units need to be designed to disappear by (sliding or folding) into pockets in the wall. To further reinforce the experience, floor and ceiling tracks should be minimal. “As if nothing was ever there.”
The best window wall units are specially designed structural units and not cheap. As an alternative, almost all window makers now offer ultra large-scale sliding door units that can, if properly designed into the structure offer a similar appearance. Above is an example of such an application and you can see why these large window walls are so popular.
Today windows should be considered and selected as permanent parts of the buildings infrastructure and not simply replaceable fixtures. Windows are now essential parts of the insulated wall system that provide light, visibility, ventilation and egress.
- Be careful if you add aftermarket, tinting films to dual-glazed windows as all warranties may be voided. The reason is damage can result from condensation or excessive heat build-up between the panes of glass when film is applied. Refer to the manufacturer s literature for additional information.
- Keep patio door and sliding window tracks clean for weep hole drainage, smooth operation and to prevent damage to the door frame.
- Label each screen if you intend to remove and store them. Handle them carefully as they can perforate easily and the frames are delicate and bendable.
- 1x per year: Clean and lubricate the sliding or cranking mechanisms. Silicone lubricants work well for these tracks and rollers. Most sliding windows (both vertical and horizontal) are designed for a 10-pound pull. If sticking occurs or excessive pressure is required to open or close a window, apply a food grade silicone lubricant available at hardware stores. Avoid petroleum-based products.
- 1x per year: Keep the operable window channel weep holes clear. In heavy rains, water may collect in the bottom channel of window frames. The makers provide weep holes to allow water to escape to the outside. Keep these bottom window channels and weep holes free of dirt and debris.
- 1x per year: Check the hardware and locks as they should operate with reasonable ease and locks should perform as designed.