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Clearing the Fog

Originally Published in MotorHome Magazine

Laminated glass is a practical solution for fixing clouded dual-pane windows that impair drivers’ vision from the cockpit

A cataract, defined as the clouding of the lense in the eye, is one of the leading causes of blindness in the world, and is a common malady among those older than 40 years of age. Aging has a similar effect on the dual-pane windows in motorhomes, causing a white fog to slowly build up between the glass to the point where the only view is one of looking through a white cloud.

Fogged windows along the sides and rear of a motorhome are a nuisance that can be tolerated until it interferes with the vision of the driver and becomes a serious safety issue.
This malady is more prevalent in older motorhomes that have been exposed for a long time to sun and/or have a broken seal. All dual-pane windows are subject to the same problem.
RV Glass Solutions in Coburg, Oregon, specializes in rectifying dual-pane motorhome windows that have failed. According to the company, fogging isn’t caused by the age of the RV, but rather the failure of the parts between the window panes. Either the desiccant-filled rubber spacer between the two panes of tempered glass – which is what absorbs moisture being pulled into the air space from changes in temperature and elevation – becomes over-saturated, or the secondary sealer on the outside of that rubber spacer fails from all the vibration and movement of the motorhome, allowing moisture to saturate the spacer and work its way into the air gap.

The area around the driver’s window was masked before special plastic pry tools were used to slide the assembly out from the opening. ,https://www.motorhome.com/wp-content/uploads/2018/06/04-MH-Window-Replacement-Removal.jpg|[2] Flange-type motorhome windows like this one have a clamp ring on the inside of the motorhome that screws to the window assembly, sandwiching it tight to the body. Removal of the window unit only takes a few minutes. Note the “fogged” window panes.,https://www.motorhome.com/wp-content/uploads/2018/06/05-MH-Window-Replacement-Window-Tape.jpg|[3] Masking tape marks the exact location of the divider for the slider window so when the new glass is installed all the parts fit exactly as they should. Care was taken in removing the rubber glass moldings, which would be reused, as they were still like-new.,https://www.motorhome.com/wp-content/uploads/2018/06/06-MH-Window-Replacement-Delgado-Spreader.jpg|[4] The metal screws that attach the cross pieces to the outer framework were removed, then a spreader was used to carefully separate the frame from the glass panes. Extra care was taken to avoid bending any of the aluminum components in the process.,https://www.motorhome.com/wp-content/uploads/2018/06/07-MH-Window-Replacement-Glass-Pane-Close.jpg|[5] Dual-pane RV windows fog internally because either the desiccant embedded in the special spacer between the panes gets saturated over time, or because the secondary (exterior) sealant is compromised, allowing water from the outside to oversaturate the desiccant. ,https://www.motorhome.com/wp-content/uploads/2018/06/08-MH-Window-Replacement-Comparison-Panes.jpg|[6] Laminated glass (right) has a thin layer of vinyl material between two thick sheets of glass, while standard dual-pane RV glass (left) has two thin sheets of tempered glass separated by an air gap. Laminated glass will never fog like the dual-pane on the left, but will not provide the same insulating properties as dual-pane glass. ,https://www.motorhome.com/wp-content/uploads/2018/06/09-MH-Window-Replacement-Removal-Tool.jpg|[7] RV Glass Solutions uses a variety of tools to remove the different panes of glass from the window assembly.,https://www.motorhome.com/wp-content/uploads/2018/06/10-MH-Window-Replacement-Window-Apart.jpg|[8] The window frame is set aside and then the individual dual panes will be removed and discarded, each being replaced by laminated glass. ,https://www.motorhome.com/wp-content/uploads/2018/06/11-MH-Window-Replacement-gasket-hole.jpg|[9] Attention to small details is critical, and one tactic used in dual-pane window reinstallation is punching weep holes in the OE rubber seals around each pane to keep water from sitting against the edge of the glass (which can affect the integrity of the spacer over time). Note that laminated glass isn’t affected by water the way dual-pane glass is.,https://www.motorhome.com/wp-content/uploads/2018/06/12-MH-Window-Replacement-New-Glass.jpg|[10] The rubber gasket is installed around the pane of laminated glass, precisely cut to fit in its new home, before sliding it into the multi-panel window frame. ,https://www.motorhome.com/wp-content/uploads/2018/06/13-MH-Window-Replacement-multiple-panes.jpg|[11] Reassembling the window unit is like putting together a puzzle, where each piece has to go back in the exact same location and in a very specific order. ,https://www.motorhome.com/wp-content/uploads/2018/06/14-MH-Window-Replacement-Razor-Blade.jpg|[12] There are a number of little tricks employed during the installation of the laminated glass, including using thin plastic tape to hold the molding to the glass as it’s being pushed into the frame, and then cutting the tape with a razor so the tape can be pulled out.,https://www.motorhome.com/wp-content/uploads/2018/06/15-MH-Window-Replacement-trim-seal.jpg|[13] One of the last steps in the rebuild process is installing a new weather seal around the window assembly. This is the primary seal between the motorhome wall and the window frame. ,https://www.motorhome.com/wp-content/uploads/2018/06/16-MH-Window-Replacement-two-workers.jpg|[14] The new window assembly is held in place as the inner frame from inside the motorhome is attached. Laminated glass weighs more than the OE dual-pane glass it replaces, so the new window assembly is heavier than before.,https://www.motorhome.com/wp-content/uploads/2018/06/17-MH-Window-Replacement-taping.jpg|[15] The area around the window frame is taped off before laying down a bead of silicone sealant. This gives a fine, sharp edge where the sealant is — and a better-than-factory finish. ,https://www.motorhome.com/wp-content/uploads/2018/06/18-MH-Window-Replacement-driving.jpg|[16] After the fogged OE driver’s-side dual-pane window was replaced with laminated glass, the motorhome was taken for a drive to test clarity. “]

Regardless of which part quits doing its job first, moisture builds up on the glass pane’s interior surfaces, resulting in the fogging effect. If left unchecked for a long enough period of time, the calcium deposits left by the water vapor will eventually etch the glass, rendering it unrepairable and permanently clouded over.

Multiple Solutions

Fortunately, there are several solutions for restoring clear vision. The compromised window assembly can be removed in its entirety and replaced if the original window manufacturer is still in business – and is still making the assembly. It’s also the most expensive option, with three-piece units likely costing more than $1,000.

A much better alternative is to remove the window assembly, then completely disassemble it so the individual panes of tempered glass can be cleaned (or replaced if they are etched) and resealed using new desiccant-embedded rubber spacers coated with the secondary external sealer. Cleaning and resealing of the OE tempered dual-pane glass is one of RV Glass Solutions’ specialties, and the company uses a proprietary process which it keeps close to the vest, so it wouldn’t let us show readers the secrets to its success.

The downside is, like all dual-pane RV windows, no matter how successful the glass cleaning/replacement/resealing process is, the same fogging issue may rear its ugly head again. (RV Glass Solutions provides a two-year warranty on its dual-pane repairs.)
A third alternative, the one many motorhome owners choose, is to replace the dual-pane windows with a single piece of thick, laminated glass. The laminated glass RV Glass Solutions uses is the same found in the automotive industry, where a thin layer of either polyvinyl butyral (PVB) or ethylene-vinyl acetate (EVA) is sandwiched between two thicker sheets of glass bonded together by heat under high pressure to form one single piece.
Laminated safety glass has several advantages over dual-pane glass, according to the company, one of which is it doesn’t shatter when broken because the plastic interlayer holds it together, adding a level of safety and security in the event of an accident or vandalism. The major downside to using laminated glass is the loss of the insulation factor provided by the dual-pane windows, which will limit the effectiveness of the windows in hot and cold weather. According to Colorado Energy, single glass, including a laminated window without an air gap, has an R-value of .91, whereas a dual-pane window with a ¼-inch air gap has an R-value of 1.69.

But the primary reason to ditch dual-pane glass for laminated is it will never fog. Hence, the reason RV Glass Solutions gives a lifetime warranty to the original owner when it replaces OEM dual-pane windows with laminated glass.

Cost Factors

The cost for either repairing non-flush-mounted windows with tempered OEM dual-pane, or replacing them with laminated glass, varies from installer to installer. At RV Glass Solutions, which is under the corporate umbrella of Coach Glass, one of the major suppliers of windshields to a number of motorhome builders, pricing for such work is very simple: $325 for a single-window assembly; $430 for assemblies with two windows; and $535 for units that have three windows.

The company has a vast reference file of RV window drawings and specifications to program computerized glass cutting machines on-site to ensure each piece is a perfect fit. It also has an abundant supply of laminated glass sheets on-site in auto green, light gray, dark gray and bronze tints, which covers 90 percent of the RV market, according to RV Glass Solutions.

Pricing on replacing damaged (etched) OE tempered dual-pane glass with like glass is more complicated. New tempered glass prices vary widely depending on a number of factors, including pricing differences in thickness and color. Sometimes the price is nearly the same as using laminated glass, sometimes it can be considerably higher. It all depends on the installer’s glass cost.

Making Time

From a time standpoint, repairing or replacing RV window glass takes about the same amount of labor regardless of the type of glass used. RV Glass Solutions says it takes a tech about three hours to R&R one of the larger multi-window units such as the three-pane “pilot window” commonly found in motorhome cockpits, and each of the techs can typically make two or three of those types of window repair/replacements a day at the massive Coburg facility.

Smaller single- and dual-pane windows take less time. Most of the motorhomes that come to RV Glass Solutions’ service centers (located in Oregon, Arizona, Florida and Indiana) are by appointment. They do accept drop-ins during the slower times of the year, but recommend making an appointment, especially during summer.

The payoff is obvious after the driver slides behind the wheel and can see clearly through the side windows – much the same as when vision is restored after cataracts are removed.

RV Glass Solutions | 888-777-6778 | www.rvglassexperts.com


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