Cleveland Ohio's
Certified Home and Commercial
Property Inspectors
WINDOW TYPES
Casement Window Type: Casement windows swing open at the side and typically the entire window opens offering a large ventilation area. Casement windows use a crank to open or close rather than pushing or pulling on the window as with most other types.
Double Hung Window: Type Double-hung windows have traditionally been the most used type of window. You open the window by lifting the bottom towards the top and/or the top towards the bottom.
Sliding Window Type: Sliding windows are much like a sliding glass door. You open a pane by moving it towards the opposite side of the window.
Hopper Window Type: Hopper windows are often used in basements. They offer a hinge at the bottom of the window and open inside.
Awning Window Type: Awning windows are the opposite of Hoppers. They swing open to the outside from the hinge located at the top. Commonly used above doors.
Fixed Window Type: Fixed windows are exactly as they sound, fixed. There is no hinge on the window and it does not open.
Bay Window Type: Bow and Bay windows create a wonderful three-dimensional feel to your home on the outside while opening your home to more light on the inside. They are available in a variety of the above styles of opening.
WINDOW REPLACEMENT
Replacing windows is expensive. Keep these window replacement tips in mind:
- Weigh partial vs. full replacement. If the old window frame is structurally sound, level, and plumb, consider changing only the window instead of replacing the entire frame to save on installation costs.
- Pick a frame material. Vinyl and clad-wood windows remain popular. Aluminum windows have all but disappeared from window replacement because they readily conduct heat. Fiberglass is available in dark colors and can be painted.
- Match your climate. Use our Ratings to identify windows with the performance you need. For example, if your home is exposed to high winds and cold temperatures, look for a window replacement that excelled at low-temperature wind resistance. Then use the National Fenestration Rating Council and Energy Star labels to match each window's U-factor and solar heat gain coefficient to your area.
- Customize performance. Even if you're buying clad-wood windows for the rest of the house, consider buying vinyl or fiberglass windows for areas near or below grade. Termites and other pests find those materials less attractive. Triple glazing (three panes of glass) can increase energy savings, but it also increases the length of the window replacement payback period.
- Check the warranty. Product warranties typically cover the seal between the panes of glass separately from the sash, frame, and other parts. They can range from one-year to "limited lifetime." So carefully read over the exclusions.
Condensation in Double-Paned Windows
Condensation is the accumulation of liquid water on relatively cold surfaces.
Almost all air contains water vapor, the gas phase of water composed of tiny water droplets. The molecules in warm air are far apart from one another and allow the containment of a relatively large quantity of water vapor. As air cools, its molecules get closer together and squeeze the tiny vapor droplets closer together as well. A critical temperature, known as dew point, exists where these water droplets will be forced so close together that they merge into visible liquid in a process called condensation.
Household air is humidified from high levels of water vapor in human and animal exhalation, plant transpiration, and fixtures such as showers and dryers. This humidity can rise significantly higher than outside air because of the insulative design of a house. Cold indoor surfaces can cool the surrounding air enough to force vapor to condense. This often happens on single-pane windows because they lack the necessary thermal insulation available to better windows. Double-pane windows have a layer of gas (usually argon or air) trapped between two panes of glass and should be insulated enough to prevent the accumulation of condensation. If this type of window appears misty or foggy, it means that its seal has failed and the window needs to be replaced.
Silica Desiccant
A desiccant is an absorptive material designed to maintain dryness within its vicinity. A common type of desiccant is silica gel, a porous plastic used to prevent spoilage in various food products. A tightly packed assortment of silica pellets is contained inside the aluminum perimeter strip of a window to dehumidify incoming household air that was not stopped by the window’s seal. If not for this substance, incoming air could condense on the glass.
Silica gel has an immense surface area, approximately 800 m²/g, which allows it to absorb water vapor for years. Eventually, the silica pellets will become saturated and will no longer be able to prevent condensation from forming. A double-paned window that appears foggy has failed and needs to be repaired or replaced.
Why Double-Paned Windows Fail - Solar (Thermal) Pumping
Although double-paned windows appear to be stable, they actually experience a daily cycle of expansion and contraction caused by “thermal pumping.” Sunlight heats the airspace between the panes and causes the gas there to heat up and pressurize. Expanding gas cannot leave the chamber between the panes and causes the glass to bulge outward during the day and contract at night to accommodate the changing pressures. This motion acts like the bellows of a forge, pumping minute amounts of air in and out of the airspace between the panes. Over time, the constant pressure fluctuations caused by thermal pumping will stress the seal and challenge its ability to prevent the flow of gas in and out of the window chamber. Incoming humid air has the potential to condense on the window surface, if it is cold enough.
Can Failed Windows be Repaired?
Inspectors should be aware that there are companies that claim to be able to repair misty windows through a process known as “defogging.”
This repair method proceeds in the following order:
- A hole is drilled into the window, usually from the outside, and a cleaning solution is sprayed into the air chamber.
- The solution and any other moisture are sucked out through a vacuum.
- A defogger device is permanently inserted into the hole that will allow the release of moisture during thermal pumping.
Inspectors should know that there is currently a debate as to whether this process is a suitable repair for windows that have failed or if it merely removes the symptom of this failure. Condensation appears between double-paned windows when the seal is compromised and removal of this water will not fix the seal itself. A window “repaired” in this manner, although absent of condensation, might not provide any additional insulation. This method is still fairly new and opinions about its effectiveness range widely. Regardless, “defogging” certainly allows for cosmetic improvement, which is of some value to homeowners. It also removes any potential damage caused by condensation in the form of mold or rot.
Window condensation will inevitably lead to irreversible physical window damage. This damage can appear in the following two ways:
- Riverbedding – Condensed vapor between the glass panes will form droplets that run down the length of the window. Water that descends in this fashion has the tendency to follow narrow paths and carve grooves into the glass surface. These grooves are formed in a process similar to canyon formation.
- Silica Haze – Once the silica gel has been saturated, it will be eroded by passing air currents and accumulate as white “snowflakes” on the window surface. It is believed that if this damage is present, the window must be replaced.
Thermal Imaging as a Detection Tool
The presence of condensation in double-paned windows means that they have failed, but the absence of condensation does not mean the window is functional. This latter fact is especially true in hot, dry environments, and when the temperature inside of a house is the same as the temperature outside. A method has recently developed that uses infrared (IR, thermal) imaging to provide a better determinant of faulty windows.
In summary, condensation in double-paned windows indicates that the window has failed and needs to be replaced. Condensation, while it can damage windows, is itself a symptom of a lack of integrity of the window’s seal. A failing seal will allow air to transfer in and out of the window even if it is firmly closed. Inspectors should be aware of this process and know when to recommend that clients’ windows be replaced.
TOTAL CARE PROPERTY INSPECTION
871 Richmond Road
Lyndhurst, OH 44124
(216) 544-9322
Cleveland, Ohio
Home, Commercial and Mold Inspections
