Conventional RV Windows
'Conventional' RV Windows can come in single pane and double 'thermal' pane configurations. With a stationary pane, and can come with an 'active' sliding pane as well. Both nested within the channels of the window frame.
These frames are mechanically fastened with screws, through a trim ring, with the wall between the interior trim ring, and the window frame itself.
Stationary glass is either chemically bonded to the frame with an adhesive, or mechanically nested within the exterior channel with a 'U' gasket circumfrencing the glass to secure and seal it.
Sliding glass operated within a 'vent track' cushioning it and reducing friction as the glass sides.
Stationary Glass Channel
Sliding Glass Channel
Screen Channel
Exterior Frame Flange
Compression Tape 'Moisture Seal'
Trim Screw Channel
Cut View Example
Functionality
*Window frame is mechanically fastened to a trim ring on the interior wall
*Window frame is sealed with compression tape, butyl tape, or sealant beind the flange of the frame against the exterior wall. Sometimes sealant is added to exterior perimeter of these frames to prevent water getting behind the flange of the frame (not required to seal, but a good practice)
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*Stationary glass unit(s) are either sealed tight within the exterior channel-with a U-Gasket around the perimeter of the glass - or - sealed directly to the back wall of the channel with adhesive, and a snap in molding around the perimeter to cover the edge of the glass (this snap in molding doesn't provide any properties to seal or bond the stationary glass).
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*Sliding glass operates horizontally or vertically within a channel. The channel is lined with a vent track to cushion the glass, reduce friction, and guide the glass. The vent track and channel have 'weep holes' cut into them. These weep holes allow water retained to drain into the stationary glass channel, and then out of the exterior channel wall of the frame above the flange. Water can be retained in the frame from rain and humidity/condensation. They are designed to drain a reasonable amount of water within 'normal operating conditions' (as specified by each RV manufacturer).
-If the sliding window systems were sealed 100% they wouldn't be able to slide at all. As water hits the sliding glass panes it deflects from the wedge molding on the center bar against glass. The filler molding which sits behind the stationary glass, within the 'outer stationary glass channel' against the other 3 sides of the sliding glass pane. Water which gets past these moldings, enters the channels of the frame, and weeps back out. Also, condensation which builds up on the glass due to interior/exterior temperature and humidity differences can drain into the tracks and weep out, so it doesn't build up and get onto/into the walls.
Sliding Glass Pane
Wedge Molding on Center Bar
Channel 'Filler' Molding
Exterior Weep Holes
Maintenance
-Window glass can be cleaned with soapy water or a non abraisive/non acidic cleaning solution and paper towels.
-Weep holes can be cleaned with compressed air, compressed air cleaning solution (i.e. 3 in 1 Vent Track Lubricant works), and a pick. Weep holes are in the sliding glass channel, to the stationary glass channel, to the exterior channel wall in the window. All need to be kept clean for the windows to egress the retained water properly. Vent track lubricant can be shot in to check if it weeps out of each channel correctly.
*Weep holes get clogged with insects, vegetation debris, and insect nests). Lifting and removing the exterior filler molding on the outside of the sliding glass pane, and checking the vent track for debris is a good practice before cleaning the actual weep holes out.
-Gaskets and moldings can be sprayed with rubber conditioner (i.e. 3 in 1 Rubber Seal Conditioner works) and wiped with a paper towel.
Pros / Cons
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Conventiional windows are a proven design, reliable, and functional.
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Glass panes are nestled safely within vent tracks, gaskets, or chemically bonded to the frames.
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Vulnerable glass edges protected within the frames.
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Properly able to seal the sash to the exterior body of the coach with the flange and adequate moisture barrier.
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Sliding glass panes allow to wide opening space for fresh air when opened.
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Easy maintenance regiment
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When in thermal (double pane) configurations- black painted frames heat the spacer up too much, and can cause the thermal (double) pane glass units to fail.
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Raw glass sliding on plastic, vinyl, felt vent tracks can cause friction and binding. Single pane glass in plastic vent tracks are prone to rattle during travel. Glass units can get stuck and be difficult to slide. Having a sub sash around sliding glass units and rollers would protect the glass and make them easier to operate.
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Windows can whistle where weep hole covers are missing.
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The forward pitch of some motorhome cockpit windows can cause water to run past the weep holes faster than it can weep out. Causing water to overflow onto the interior.
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Excessive amounts of water (extremely heavy rainfall, and washing) can overwhelm the capabilities of the weepholes, causing leaks on the interior.