Updated 11/8/23
People, especially in the RV space it seems, will pontificate online about a topic and need to know what they are talking about, but don’t. I started The RV PHD to help people learn from the best practices and information available across the RV industry.
Dual-pane RV windows fit squarely into that category.
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A dealer-based influencer recently posted a video viewed by tens of thousands, claiming that dual-pane windows were an industry scam, made from two pieces of glass glued together, and a waste of money. The video was for this salesperson to show their concern for and support of RV buyers. Since most of his organization’s clients probably don’t buy RVs with dual-pane windows and don’t stock RVs with this option, it was an easy clickbait choice to put down manufacturers and make them look better. This tactic is widely accepted in marketing circles to get attention and can help solidify an online audience. The information was incorrect, however.
Dual-pane windows are not a panacea for improving energy efficiency in RVs, and NO RV is nearly as efficient as a modern home. “4-season” RVs are made to allow you to use them in below-freezing conditions, but only to a point, and it will be expensive to keep the environment comfortable and the plumbing system unfrozen.
I have been RVing for 50 years this year and have been in the business since 1998. I was ten years as a full-timer from 1998-2008, spending most of the winter months in the Northeast in modified motorhomes. I have tested RVs in this environment and am considered by some to be an RV technical expert. But let’s not just take my word for it.
A 2011 article in Architect – The Journal of the American Institute of Architects discusses measuring windows’ energy efficiency. It refers to the Efficient Windows Collaborative website that details the parts and designs of windows.
The influencer’s video stated that RV dual pane windows are no more than two panes of glass glued together, each with an R-factor of 1. I have heard this statement before, and while the R-factor statement is correct as far as it goes, the rest is poppycock.
First, the window that the video creator was describing is a laminated safety glass window, which is used in RV windshields along with some other places. These have no unique insulating factors. He is not describing double-pane windows.
Window energy efficiency is rated using a U-factor, not an R-factor. R-factors are no longer used in the RV industry because of the stark differences in efficiency in the structure due to wall design and materials. The US Department of Energy states, “U–factor is the rate at which a window, door, or skylight transmits non-solar heat flow.” But solar heat flow is also a consideration.
As you can see above, RV dual-pane windows are double-e-pane windows. These are two panes of glass with a separator that creates an air gap between the layers. The air gap offers some thermal transfer protection while not filled with an insulating gas in the RV windows. Further, if the window is tinted, that applied film also offers some solar transfer protection. The window’s aluminum frame and the aluminum framed laminate wall offer an excellent heat transfer medium.
So, given this information, what do RV dual-pane windows gain for the RV owner who intends to use the RV in temperature extremes of hot or cold?
Cold weather is the toughest to overcome comfortably because of the tendency of heat energy to move from a hot area to a cold area. Not only are we using the heating system to heat the interior space, but we are also heating the environment! The inefficient propane furnaces used in the RV industry waste most of their BTUs in the exhaust. The rest is absorbed through the weakly insulated body. Metals are better conductors of heat for sure, combined with roughly two-inch thick walls.
The double-e-pane windows reduce condensation on the glass more than anything else. The cold weather heat transfer is reduced, but the difference is minimal with so many other areas of poor insulation. The condensation builds on the windows, collects in the window track, and depends on the open drains to drain the water to the outside. The problem is that these can freeze up when too much condensate is present, which causes a backup onto the interior wall and causes wood paneling decay and delamination.
During the summer heat, the amount of heat transfer is also notable. Combined with tinting, the sun’s heat is felt less than with a single-pane window.
To be clear, when a curtain or shade is drawn over any window in frigid conditions, the insulating factor provided by the curtain or shade will allow condensation and frost to form on the window, but far less than would otherwise develop. Keeping the RV air as dry as possible is essential by using a dehumidifier or venting slightly during the day.
RV double-e-pane windows are an added expense when ordering an RV but will increase interior comfort and energy efficiency and slightly reduce sound transmission, making the interior quieter. While not for everybody, they do work and will make life in the RV better.
11/8/23 update: Big Truck,Big RV released a video today testing RV dual pane windows, and clearly indicates the benefit of having them on an RV.
The RV PHD Newsletter is a reader-supported publication. To receive new posts and support my work, consider becoming a free or paid subscriber.
