Frame-Less RV Windows
Frame-Less RV Windows can come in single pane and double 'thermal' pane configurations. With stationary glass units (panes) and active glass units which either vent open, or slide open (sliding configurations are mainly used in the cockpit of motorhomes/motorcoaches). Frame-less windows have an all glass, modern, and flush appearance. Adding desireable aesthetics to modern RVs, motorhomes, and motorcoahces.
Frame-Less windows typically contain an aluminum 'sub-frame', resembling many similarities as the frame of a 'conventional' RV window. These sub-frames are mechanically fastened to a trim ring on the interior wall, with a moisture barrier behind the flange of the frame. Some, select frame-less window manufacturers', manufacture a self contained glass window which chemically bonds to the exterior wall of the RV with no metal sub-frame-These are more typical on later model motorhomes/motorcoaches.
Exterior Flange
Foam Moisture Seal for Vent Glass Pane(s)
Interior Sill Lip for Screen Clips to Mount
Side View Example
Sill Channel
Exterior Sill Lip- Thermal Pane Frame-Less Units Interior Pane rests and seals here.
​
Functionality
*Most Frame-Less Window frames are mechanically fastened to a trim ring on the interior wall. Select manufacturers produce Frame-Less Windows which are self containted glass windows which chemically bond to the exterior 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)
​
*Stationary glass unit(s) are sealed and chemically bonded to the outer flange of the sub-frame with urethane (best practice), butyl, or high viscosity tape. The adhesive used here must bond the glass unit(s) to withstand travel, climate, and intense UV heat (as the privacy gray glass used in most Frame-Less windows retains heat very well).
​*Most Frame-Less windows contain 'venting' glass units as their active glass pane(s). These glass units are chemically bonded to a hinge at the top with urethane (best practice), butyl, or high viscosity tape. This hinge allows the glass to swing out from the bottom of the glass, when operated. The manual actuator is typically a twist knob connected to 'scissor arms'. These 'scissor arms' have vinyl/plastic wheels on the ends which allow the 'scissor arms' to swing in and out while passing through a 'track bar' which is chemically (by the same methods as stated above) bonded to the bottom of the glass. This action allows the lower portion of the window to swing in and out. When pulled in tight, the 'venting' glass pane(s) seal against 'D-foam' weather stripping, which is located on the exterior flange of the sub-frame. The pressure of the glass against the weather stripping seals from water under normal operating conditions. There is typically a set of gaps in this foam seal at the bottom of the window. These gaps allow condensation or any small amounts of retained water (against the glass) to weep out.
*Some Frame-Less windows, typically in cockpit areas, contain a sliding glass unit within a channel in the frame. These sliding glass units are nested within a vent track, same as a conventional RV window. These channel and vent tracks contain weep holes which allows retained water within the channel to weep out of the frame.
​
*Escape (Egress) Frame-Less windows have the same hinge on top, allowing the glass to swing out at the bottom. There is a similar extrusion as the 'track-bar' which allows it to hook or clasp to hardware on the interior of the lower sill of the frame. This allows the frame-less pane to swing out, freely, allowing an emergency exit from the RV. Careful opening these for airflow, because most of these frame-less escape window panes will un-hook at the hinge when close to, or at the 45 degree point. Also, consider the height of escape windows, some come with a long way down to the ground. How often have you seen anyone stage a ladder outside of their escape window(s) when camping? Hehr 6400 Series Usage Guidelines
​
*Active (Venting and Sliding) Frame-Less glass panes are not 100% sealed. As noted above, they are designed with gaps in the foam weather strip and weep holes to allow condensation and retained water to escsape. These features allow for air and moisure to enter and exit the interior of the RV.
​
*Frame-Less glass has a black border around the interior perimeter. This boarder is required to block the UV sunlight from making contact with the urethane adhesive (same principle you can see on your car/truck/RV windshield) which chemically bonds the glass the the frame, hinge, and track-bar. This black border also covers where the glass and frame meet, to block that area out, and create a sharp and flush appearance.
Lower 'Track Bar'
Top Hinge
Black 'frit' Band
Maintenance
-Window glass can be cleaned with soapy water or a non abraisive/non acidic cleaning solution and paper towels.
-Check the weather stripping on the outside flange of the frame (behind the vent/escape glass panes) for dry-rot, cracks, and adhesion (can fall off and hang down as well). If weather stripping is falling off, they can be re-attached with an RTV silicone (reccomended), expoxy, or similar adhesive.
-Check the adhesion of the vent/escape glass panes to the hinge(s) and track-bar(s). It is a common problem where these extrusion hardware pieces become un-attached from the glass. This would allow the glass to 'flap' freely in travel and/or fall off. If any are loose, we can coach you through how to properly re-attach/bond them back to the glass- without having to pay anyone to do it for you.
*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
-
Sleek, Sharp, Modern, and Appealing looks with the 'all glass' and flush appearance.
-
Edge of the glass is exposed in most all applications of Frame-Less Windows. Tempered glass is strong, however it is very sensitive on the edges. This 'Achilles Heel' increases the probability of it breaking. If a small object from the road strikes the edge of the glass, the pane will likely shatter. This can be hedged against with an edge protector, on the drive (forward) direction of the glass edge.
-
Venting panes do not open very far. This restricts fresh air flow for RV'ers who prefer to open their windows in nice weather.
-
Escape (egress) panes can fall out when opened too far, most RV'ers are not aware of this, until it is too late.
-
Thermal (double) Pane Frame-Less glass units are more susceptible to seal failure and fogging. The secondary sealant used behind the desiccant is typically polyisobutylene, which cannot work properly with the retained heat the exterior glass pane builds up from the UV light. The desiccant spacer and secondary sealant are set onto the black band around the interior of the glass, which draws the heat in. This causes swelling and contraction of the secondary sealant, and ultimately seal failure. It is also common for these glass units to separate on their own over time. A high viscosity urethane sealant can perform better in this application, than the polyisobutylene, while providing a proper moisure vapor barrier.
-
Some of these Frame-Less vent panes can have a tendancy to separate from their hardware, without notice. Primary adhesive failure is the cause of this.
-
Screens on these Frame-Less windows are a common customer complaint. They can be difficult to snap back into the interior sill wall of the frame.
-
In a cockpit window configuration with a conventional sliding glass unit used within the Frame-Less window assembly- If the sliding glass unit is compromised it can be difficult to replace just the sliding glass. As the frame has to be pulled from the opening (which is typical in a sliding glass replacement). However, where the frame separates to open it up (to install a new sliding glass unit) the exterior stationary glass pane(s) are chemically bonded to the outer flange and center bar(s) of the frame. The stationary glass must be cut free (even removed in some cases) for the frame to be able to separate and open up for the installation of the new sliding glass unit. Extra labor and extra materials is required in most cases.
-
Weep holes in cockpit Frame-Less windows are very difficult to clean out (covered on the exterior by the stationary pane on the front, and by an acrylic trim over the exterior flange on the lower portion of the rear of the frame. Also we have seen where the manufacturer has allowed urethane adhesive to cover the weep holes. The glass has to be removed and in most cases replaced (due to possible damage when removing), top clear the adhesive from the weep holes.
​