What makes a 4-Seasons RV the true All-Weather unit suitable for comfortable RV-ing in weather ranging from hot summer, through rainy days to icy winter....
As the concept of recreation “extended” well beyond the boundaries of traditional summer vacations, “All-Seasons” RVs became more and more popular.
Unfortunately, the RV industry is not regulated so well as the automotive one, so the definition and meaning of All-Season (4-Seasons) RV is quite vague and largely left to the manufacturers. As the result, on the market there are plenty of RVs promoted as 4-seasons units but besides higher price and weight nothing else is really obvious.
In this presentation, we would like to discuss basic elements of what makes a given RV the true All-Seasons unit.
Before we go farther first let’s decide what really means All-Season RV-ing. There will be big difference in terms of requirements (and price) if you want to:
Bighorn 5th wheel - an example of an RV designed for full-time living
In southern and moderate climate-zone conditions it may be relatively easy (and certainly not too costly) to enjoy all-year RV-ing. The real challenge brings the subarctic climate zone covering US northern states and across the border large swaths of Canadian provinces (not even mentioning “Big North” - Canadian Northern territories and Alaska). That is why some prefer to call RVs designed for year-long use as “All-Weather” units. This name really reflects RV’s ability to withstand harsh weather conditions ranging from hot and humid summers, through rainy periods to cold, windy winters.
Some will also differentiate the meaning of “All-Season” RV from the point of view of length of the trip arguing that short trips do not require as much of cold weather protection as long ones (including “Full-Time Living”). Well, I would say that the main difference is rather the level of comfort (or lack of it). Because once the temperature goes permanently below the freezing point what matters the most is:
Will your RV (water pipes, tanks and drains) survive winter’s attack? (and your pocket the cost of repairs)
Northwood Arctic Fox label shows what really makes a True 4-Season RV: It is ability to offer RV-ing comfort in All-weather conditions including hot summer (Sun), Rainy days and cold Winter
However, what really makes the difference in terms of “All-Weather” requirements is the camping environment. Understandably, Off-Road and Off-Grid conditions make the RV-ing much more demanding even in moderate climate zones. Needless to say, that the extreme weather conditions (arctic climate in winter and “subtropical” for summer) will substantially rise the requirements to be met and cost of all-weather RVs.
The most important factors defining RV’s all-weather readiness are:
Before we start, let’s make it clear – there is no perfect All-Weather RV available on the market. And it’s not only due to the fact that “perfection” cannot be achieved at the “reasonable” cost, but also because so far there are no clear criteria defining the set of “all-weather” parameters and corresponding requirements. That is why for enthusiasts of all-year RV-ing we suggest taking practical approach of looking for and RV just “good enough” that will meet their individual needs. This approach will safe tons of frustration, time and definitely a lot of money.
Below you will find important elements of the “All-Weather” RV design so you will be able to make an educated decision when it comes to your “all-seasons home-away-from-home”.
Refection (Grand Design RV) and crucial elements of its Arctic 4-seasons package:
Ideally, the chassis of all-weather RVs should be corrosion resistant. Thanks to popularity of lightweight designs many contemporary mid-range models have aluminum chassis what makes them perfect candidates for year-long RV-ing. However most larger rigs due to increased load are still built on stronger, but corrosion-prone steel chassis. Typically, they are corrosion protected (usually powder-coated) what under normal circumstances should guarantee long-lasting rust-free operation. Winter changes this picture due to massive use of salt on northern states roads (so-called Salt-Belt states) and in most Canadian provinces.
It is then suggested to carefully wash RV’s underbelly after winter season to remove layers of accumulated salt. Otherwise, at higher temperatures the salt in contact with rain water and/or humidity in the air will start accelerated corrosion process. Keeping the RV in the heated garage will also have devastating effect when salt is not washed out. Note that off-road RVs exposed to gravel and debris may require periodic inspections of the underbelly and eventually additional protective coating to prevent corrosion.
Overwhelming majority of modern recreational vehicles have wooden or aluminum frames or are frameless (all-fiberglass shells).
Not surprisingly, for long the wooden frames were the most popular and familiar solutions. Indeed, the wood is not only inexpensive but also well-known for its good thermal insulation properties essential in extreme climate zones. Unfortunately, wood is also prone to rot, mold and with it to accelerated degradation severely limiting RV’s lifespan. Unlike our residential houses, RVs are exposed to shocks and vibrations stressing hermicity of the shell.
This creates an “opening” for mentioned wood degradations. Due to much more limited interior space the humidity generated in bath, kitchen and even by our breaths in contact with colder layers of the box structure (shell) will cause water condensation. Additionally, the rain and melting snow from the outside will add to the “misery”. As the result, the wooden-frame RVs (including roof and floor structure) are not the best all-weather candidates. Their longevity will be seriously challenged!
LivinLite aluminum chassis proves that it is possible (unfortunately LivinLite does not make all-weather RVs)
Modern aluminum frames are not only much lighter (being “lite” has additional advantages) but also resistant to rot and mold induced decay. However, in difference to wood, metals are good conductors of heat. In other words, the aluminum frame creates “thermal bridges” in the structure of the shell. This in turn weakens the efficiency (overall R-factor) of the thermal barrier. All-in-all, the long lifespan of aluminum-frame shells makes them the solution of choice for all-weather RVs.
In All-Fiberglass RVs, half-shells (upper and bottom) are made in the molding process and then both are “glued” together in the final step. The final result is a “self-supporting” (frameless) shell with high level of integrity (hermicity) and good thermal properties. Theoretically such shell should be preferred solution for all-weather RVs. Unfortunately, it is not the case for the following reasons:
Oliver Trailers - one of the molded-fiberglass "half-shells" at the early stage of the production
While the popular "Ollie" is not the all-weather camper you may be interested to see this innovative design: --> All fiberglass Oliver Trailers
On the positive side, we can see already attempts to improve at least some of weak spots of all-fiberglass RVs. For example, some companies (Lil-Snoozy) in order to improve the overall R-value of the shell, insert during the molding process extra sheets of insulation between the layers of fiberglass. This is already a big improvement of the all-fiberglass technology.
Much more promising all-weather approach was undertaken by Oliver Trailers. The company makes their trailers from two molded fiberglass shells: inner and outer (each one made up from two half-shells). This design opens new possibilities, like insertion of adequate insulation in-between inner and outer shells and as a “side-effect” – hiding most of wiring and plumbing between shells. As the result, to overall R-value of the insulation can achieve required levels at critical locations (roof, walls, floor) and water pipes can get much needed protection. Additionally, the design (molding process) can be easily modified to allow for installation of holding tanks and draining valves in an enclosed, insulated and heated underbelly.…. (to be seen)
Insulation barrier is the most important factor determining the cost (heating or cooling) and comfort of RV-ing. As mentioned earlier, there are no commonly accepted standards determining minimum R-values of insulation for all-weather RV. Basically each manufacturer (Keystone, Northwood, Heartland, Lance….) comes up with its own ideas, designs and specifications.
Based on currently available models of all-weather RVs you can expect the following:
Roof is the most important insulation barrier. In the winter, the hot (warm) air due to natural convection accumulates at the ceiling so this is the place of highest gradient between interior and exterior temperatures. Similarly, during the summer, roof exposed to sun is the hottest spot in the RV so once again it is the area of highest gradient between exterior and interior temperatures. As the result, the roof should have the best insulation (highest R-value) throughout the box. Practically you may find roof’s “equivalent” R-values of up to 38.
It should be noted that side walls may be heavily exposed to the sun (hot summer) and cold winds (winter). While opened awning and in general shade may greatly limit the impact of direct sun exposure, nothing can protect the box from “arctic” winds. That is why higher R-values of insulation in sidewalls are welcomed. Practically, sidewalls are the weakest part of RV’s insulation barrier due to windows (see below).
Good insulation of the main floor has huge impact on our comfort especially at low temperatures (after all we walk on and live in close contact with the floor). In general, the insulation of the floor in all-weather RVs is “combined” with the insulation of the underbelly where all critical water systems (pipes, valves and holding tanks) are located.
Good news is that we can easily improve the overall “underbelly and floor” protection by installing skirts along the RV. Skirts efficiently protect this vital area from freezing winds (keep in mind that the floor is sitting on the massive frame (steel or aluminum) – both very good heat conductors).
Slide-outs are also “weak” spots in RV’s overall thermal protection. Sticking out from the main structure they are largely exposed to weather elements (be it scorching sun, arctic winds or rain….).
Front caps usually have better thermal protection than sidewalls. It is mainly to prevent the interior from freezing when on the road. High speed towing on highways creates strong headwinds that on longer trips can dramatically lower RV’s temperature. Please note that this is the most vulnerable situation for an RV (trailer, 5th-wheel, truck camper etc..), because usually the heating is turned off. While you can bring the temperature up once on the campground, it may be too late for all water installations and holding tanks.
An example of the "Radiant Barrier" - here Astro Shield reflective insulation (thin-film metal layer over the thick bubble substrate)
We can dispute these values, but on the other side we have to accept the reality unless you want to DIY (not suggested in the case of thermal insulation as any such work will destroy the integrity of the box’s structure).
What is undisputable however is the type of insulation used by manufacturers. The familiar to most of us residential insulation (fiberglass-wool mat) can be used ONLY in horizontal sections of the RV (roof and floor). Rigid foam-blocks should be used in all vertical sections (walls, front cap…). This is due to the possibility of the sagging effect caused by shocks and vibrations that an RV is exposed to during its lifetime. In other words, the residential insulation may “migrate” down the wall leaving empty spaces behind. You may not notice this degradation during the traditional vacation season, but certainly you will feel the difference (energy bills and lack of comfort) in extreme weather conditions (hot summer of cold winter).
Note: Any insulation barrier acts as a “High Resistance” heat conductor (insulator) or as a “reflective” barrier. The R-value physically describes the “heat resistance” of an insulator. Higher Heat Resistance, higher R-value and better ability to “maintain” interior temperature (either low when cooling and hot when heating). In other words, more difficult for hot air to penetrate RV’s interior from the outside (summer) or to escape from the RV outside (winter).
You will notice however that these days manufacturers often make use of “Reflective” insulation barriers. They are characterized by an “equivalent” R-value as they do not transfer the heat (so do not have a true “Thermal Resistance”) but rather reflect the heat back to the area where it comes from. In practice, it is a sort of shiny metalized reflective film deposited on the polyethylene “bubble” substrate acting as the carrier and barrier for the heat transfer (conduction). Some of the reflective insulation products used in RV industry are AstroShield and Astro Eco.
The most common solutions for RV siding are laminated sheets of aluminum or gel coated fiberglass. Also popular are panels of laminated luan or Azdel as they are used anyhow to add strength to the “box”.
Luan (Lauan) plywood is very similar to the traditional one. Its main advantage is substantially lower weight - critical for RVs in the era when "Lightweight" is a word of the year (actually for the years ahead)
The luan (sometimes also spelled “lauan”) is a plywood made from tropical (South-Asian) trees. It is the preferred solution over traditional hardwood plywood due to its significantly lower weight so crucial in modern RV industry. Typically, it comes in ¼ inch panels either laminated (if exposed to weather elements) or just as raw panels if covered by siding. As mentioned earlier, use of wood in all-weather RVs is not the best practice due to the risk of rot and mold. While its use is less critical in traditional “summer” RVs, winter temperatures will cause high level of condensation on any element exposed to exterior temperatures what will be highly destructive to any sort of wood.
An example of an RV sidewall with Azdel
Azdel is a thermoplastic composite material efficiently replacing wood (plywood) in construction of the RV box. It is stronger, lighter and provides higher R-value than the equivalent luan panel at the same time eliminating possibility of mold, mildew and rot. Given these facts, Azdel is the material of choice for “All-Weather” RVs. Unfortunately, Azdel’s higher cost so far limits its widespread use in the RV industry.
If it comes to the choice between aluminum and fiberglass siding, the preference should go to multilayer fiberglass. The aluminum is simply good heat conductor while the fiberglass is a thermal insulator. While due to small thickness of aluminum sheets (0.04” max) it will NOT be a dominating factor in overall thermal barrier, it certainly will have some negative impact, especially in windy winter conditions.
Another important argument for multilayer fiberglass siding is its “continuous seamlessness”. In contrast, the aluminum sheets are attached to the frame by rivets or metal fasteners what weakens the overall integrity of the “box” structure making it prone to leaks.
Insulation of exterior compartments
Exterior compartments in all-weather RVs usually benefit from the fact that the underbelly is enclosed and heated. Obviously, there is no need to keep there “room” temperature (it will be costly requirement), however it is good practice to prevent stored objects from icy weather. Part of the protection are insulated compartment doors and good seals. If this is not the case, try to find model where at least the main pass-through storage meets these requirements.
RV windows, similarly as their “residential siblings” are weakest spots (largest sources of the heat loss/heat penetration) in RV’s thermal protection barrier. And honestly there is no good solution to the conflicting requirements of having large panoramic windows and at the same time low energy bills.
Construction of the thermal, dual-pane window (Courtesy of Roxy Glass)
Currently, the only viable solution proposed by RV industry are “Dual-pane” windows. Technically speaking, the dual pane window consists of two hermetically sealed plates of glass (panes) with a special gas in between them. The gas must be neutral (for safety reasons) and have better thermal properties (higher R-value) than the air. Practical choices are Argon (R-value about 1.5 times higher than air) and Krypton (R correspondingly about 3-times higher than air). Unfortunately, Krypton is much more expensive than Argon so its use by RV industry is rather limited to luxurious rigs. Additional factors improving R-factor of windows are: low emission glass and reflective coating (thin metal film). Needless to say, that equally important is a low conductivity framing (fiberglass or vinyl instead of aluminum). Usually RV windows (regardless if they are dual- or single pane) are dark-tinted. Dark tint not only offers better privacy but also reflects some heat adding extra benefits
How the numbers look in practice? Well, the typical home window may have R-value of 1 to 2 (maximum). However, replacing air with Argon, traditional glass with its low-E version and applying reflective coating may increase R value to the range of 4-5. It’s still not impressive compared to the R-values of the “box”, but hey, by far better than the R-values of traditional, single pane windows.
In some demanding cases (for example residential homes in Alaska) you may see triple-pane windows. While they offer increased thermal insulation (higher R-value) they are simply too heavy and thick for application in RV industry. In fact, the dual-pane windows already add significant extra weight to the RV.
Most RVs (even medium sized models) include at least one (if not more) skylights. By definition, they are placed in ceilings at “strategic” locations throughout the RV like bathroom, galley, bedroom. Well, when looking for all-weather RV you may have to lower your expectations. As mentioned above, the ceiling should have the highest level of thermal insulation. In a summer, the roof is directly exposed to the sun so the insulation must be highly efficient to prevent infiltration of the heat. Correspondingly in a winter, the interior heat will accumulate near the ceiling, so the mentioned insulation must prevent the heat from escaping outside. The bottom line is: in all-weather RVs the R-value of roof’s insulation is the highest one (see above typical numbers) and any “hole” (weak spot) in the ceiling’s thermal barrier has serious effects. That’s why usually all-weather RVs have limited number of skylights (if any). Those installed should be also dual-pane ones!
It’s worth to mention that dual-pane windows have good sound-proofing properties, (something that can be priceless on a busy campground)!
Note: This clear thermal improvement comes at the cost. And it is the longevity of dual-pane windows. When installed in residential homes, they may last for 12 to 20 years. However, RVs bring the extra stress due to inevitable shocks and vibration inexistent in “stationary” applications. As the result, the dual pane windows may lose their hermeticity much faster (and certainly they will). And the consequences are not user friendly. You may still be able to live with higher energy bills (or lower comfort), but for sure you will have hard time to accept foggy windows. And this is what will happen when exterior air with some level of humidity will infiltrate the interior gap between glass panes. Sorry to say it, but the only practical solution in such case is to change the windows but it is a costly event.
Unfortunately, there is no much you can do about it so the best advice is: enjoy your trips as long as you can.
Well, there are still some good “grand-mama”-era habits that can help and they do not cost much. The shades over windows will always add into overall R-value of the thermal insulation. So, when you are NOT watching the beauty of the surrounding nature, gazing at the nightly sky in the comfort of your RV’s recliner (theater seat, sofa, bed….) use the shades. They will decrease the heat convection/radiation between the window and the interior of your RV. While it may be a “tough call” during the day in nature, you should certainly do it (not only for the privacy reason) during cold nights.
Underbelly houses almost all vital RV systems of which in all-weather models some most critical are plumbing, holding tanks, dumping valves, utility hook-ups including external shower etc… In general it is everything containing water due to the risk of destruction when frozen. That is why every all-weather RV must have an enclosed, thermally insulated and heated underbelly. The heat may be provided by running “non-insulated” main heating ducts through the underbelly (and some storage compartments) or by a dedicated heat distribution system.
An example of an enclosed underbelly - here Canyon Trailer (Note: it's not an all-weather RV)
However, the hot air circulating system is not enough to prevent potential damage. While on the campground you will certainly turn on your furnace (if needed), but in most cases, it will not happen when on the road (mainly due to security reasons). Long hours on the highway especially in “cold headwind” environment will certainly bring RV’s interior temperature (including the underbelly) down, potentially below the freezing point. That is why each all-weather RV must have a secondary heating system for water installations. Usually these will be heating pads running on an auxiliary battery.
It should be noted that underbelly’s interior temperature does not have to be as high as in RV living sections. It must just offer some reasonable safety margin above the freezing point.
Skirting helps to keep RV warmer
See details at: --> RV skirting
The extra benefits of the enclosed underbelly are: lower aerodynamic drag on the road (so better fuel efficiency), protections from debris (especially important for off-road models) and protection of all “stuff” traditionally mounted under the floor) from rain water, mud etc…. (eventual rust, rot …)
In general, steps in RVs are often forgotten (in other words, it is assumed that are where they supposed to be and there is no reason to worry about). While it may be justified approach in traditional summer RVs, it will be very wrong in the case of all-weather models. Accumulated snow and/or ice can make them a “deadly” trap. So here some suggestions:
Please note however that the traditional anti-slippery surface offers protection when wet (good for rainy season). Accumulated snow and/or icy-rain will make it mostly useless.
Needless to mention that the aluminum steps have clear advantage over prone to corrosion steel ones.
Awnings and Slide-out Toppers.
Awnings are greatly appreciated during traditional RV-ing season. They offer shade protecting from scorching sun and “shelter” in the case or rain. Protection from direct exposure to the sun is also beneficial for the RV itself (precisely for the A/C system). It simply makes the first “outer” barrier decreasing the heat-stress on sidewalls and more importantly on the weakest spots in RV’s insulation –windows.
During winter season, traditional awnings are rarely used. Exposure to snow (and potentially damaging heavy load), possibility of strong winds – are convincing factors to keep them closed.
The use of slide-out toppers has merits throughout the whole year. In summer, they protect slide-out roof from debris (mainly leaves and small branches when parking under the trees). They also provide “some” heat-barrier protecting mentioned roof from direct exposure to the sun. The use of slide-out toppers in winter is a bit trickier. The accumulated snow (or even worse- icy snow) on the slide-out roof will make its retracting process at best painful if not impossible. It is up to you to decide what is easier – remove the snow from the topper or from the slide-out roof. However one thing is clear – the damage to the slide-out (especially seals) may be much more costly than the potential damage to the toppers.
Note that slide-out toppers are much smaller than their “traditional” cousins on the sidewalls so they are better prepared to survive the snow and winds.
See also --> Best winter Travel Trailers
Well, we just finished the short overview of Construction Requirements for an All-weather RV. Next are coming the following topics:
Please continue at: --> Four-Seasons RV: Climate Control