Introduction

The concept of being able to hitch up and explore a variety of environments and climates is thrilling.  Picture this:  A family sets out for a summer adventure, with a travel trailer in tow.  Parents in the front seat, windows down.  The warm breeze blowing through the vehicle with kids playing car games and watching a new world go by in the back seat.  Imagine the many exciting adventures that lie ahead for this family.  Now, consider these mental images:  What will the weather be like?  Is the family traveling somewhere warm?  Perhaps a lake or mountains where the outdoors will be explored?  Nice warm days, cool nights. It will be a comfortable vacation.  After all -- that’s what vacations are for.  


There’s a reason this is a rather iconic and ideal image.  This is exactly what the vast majority of today’s travel trailers are designed and built to do.  This is what I call a “3-season” trailer design.  The primary travel season for most travel trailer users is summer.  A warm summer, but not too hot, with mild temperatures, light breezes, and yes, always comfortable in shorts. The reason we call this 3-season is that the trip may extend into both Spring and Fall.  The trailer is built to handle exactly this type of moderate climate conditions.  


Now imagine this scenario:  It’s April, and that same family is on that first camping trip of the season.  Well prepared in the 3-season travel trailer, they notice large clouds forming on the peaks of the mountains ahead.  As they gain elevation it starts to rain, then sleet, and finally as they arrive at the campsite there are a couple inches of snow on the ground.  Only then will they discover that the 3-season trailer is not designed to perform well in hot or cold environments. 


This is when the issue of the 3rd and 4th seasons come into play.  Winter is the enemy of travel trailers.  Even with a strong furnace and a couple full bottles of propane, in short order, the trailer will not be able to “keep up” with the cold temperatures and things will start to fail.  There is simply a limit to how well the system is designed to resist hot and cold temperatures.   And it’s not even the heating system’s “fault” - it was working as designed.   The issue is more fundamental.  The problem is the travel trailer wasn’t designed or engineered to be used in all 4-seasons.  


Joanna and I have both camped and lived full-time in countless travel trailers for years, and I’ve discovered that no two trailers are the same.  While one trailer design may be fully functional and comfortable down to 20º, another seemingly identical travel trailer may start failing at the point of freezing.  This type of trailer I do not consider “Luxury.”  A Luxury Travel Trailer, by definition, is created to take you farther, to do more, and provide the best living experience in most living conditions.  


In this article, it’s my goal to help clarify what makes a Luxury Travel Trailer 4-season capable and what affects the performance in all sorts of climates.  


Why is 4-Season Capability Important?


A typical travel trailer is not designed to respond to a multitude of environmental conditions.  However, our amazing world has countless places and experiences that are far from “Sunny and 75.” 


This awareness is especially important for people who call their trailer home, year-round -- they are known as “full-timers.”  The major difference between full-timers and the recreational camping family described earlier is simple.  One family has a traditional home they can return to after their trip.  The full-timer has no such option.  This is the key difference between a Recreational Vehicle and a Living Vehicle.  One is designed for recreation, spanning a short period of time, the other is designed for living as a primary residence to call home, full time.  


When winter comes, or a heat wave makes cold weather trailer-living impossible, the family puts their trailer in storage and returns to the comfort of their bricks and sticks home.  When winter arrives for the full-timers, the trailer must continue to perform to suit the very real requirements of the environment.  At this point, the full-timer has two options:  follow 75º by moving to a more temperate locale, or upgrade their HVAC system.


As has been done for decades, the trailer may be moved to warmer climates, and this is by far the most common solution.  A mobile lifestyle lexicon has even been created, with such terms as  “snowbirds,” which are those who fly south for the winter to safely continue living in their full-time traveling home.  Relocating the trailer out of the cold is one way to live year-round, and frankly seems most enjoyable to me!  After all, I too enjoy “sunny and 75” -- most of the time.


But what happens if you are not able to relocate or you actually want to be in a frigid environment?  For example, I love skiing.  Being first on the mountain is important, after all - fresh tracks.  Being able to park overnight at a winter resort parking lot in December means I will always be first up on the chair lift. It is simply awesome.  Or, what happens if work demands require you to be in a location during colder months?  Or, what about when a sudden Arctic cold front comes in early September, and the wind chill is -10º?  Every one of these examples isn’t only possible, but has happened to me.  And more importantly,  these dramatic weather conditions are no longer the exception -- they are becoming ever more common with our ever-changing world climate. 


A true luxury travel trailer should be designed to survive, even thrive, in all types of weather conditions and climates.  Knowing that you have options is the key to owning a true 4-season capable trailer.  This is what I call the freedom of choice.  Understanding exactly what makes your trailer able to withstand very hot and very cold environments means you have better options, to choose where and when you travel -- and how long you stay there.  

What Makes a Trailer 4-Season Capable?

Young, or young at heart, recreation today is all about total freedom.  More than ever, Luxury Travel Trailer owners are taking their units off-grid and challenging the limits of what climates they may travel.  


When it comes to 4-season capability, there’s one very simple question:  How easily does the trailer perform in very hot or very cold climates?  The answer to that question is complex and involves quite a few variables.


What to consider when buying a 4 Season Travel Trailer?


When considering a 4-season off-grid travel trailer there are 10 very important concepts to consider:


4-Season Comfort

I love camping.  I have a sleeping bag designed for sleeping in the snow.  Now camping in very cold weather is not particularly my  idea of a good time, but I love being over prepared.  That sleeping bag is rated down to 20˚F.  So I bought it thinking I’d planned for plenty of buffers should temperatures get below freezing when camping.  Only after buying it did i realize that this fancy 20˚ rating was in truth a “survival” rating, not a “comfort” rating.  The comfort rating wasn’t even below freezing.  I felt duped.  


It’s simply not enough for a travel trailer to have a 4-season “survival” rating.  A proper 4-season travel trailer should be designed to thrive in all conditions, and in the most comfortable manner possible.  They must be designed to withstand the demands put on the critical, life-giving systems.  A luxurious design takes into consideration such options as heat resistance, insulation, thermal breaks, heat/cooling loss, and freeze protection, all working together in harmony to create the simple condition: comfort.  


Outside of the actual design and function of the trailer’s well appointed interior, the bottom line of 4-season comfort is answered by the trailer’s ability to maintain interior temperature at a comfortable level in either hot or cold environments. However, the challenge for most trailers is they are often woefully under insulated and the installed systems are under-equipped. This can be a real challenge with walls that are just 1-½” to 2” thick! A typical bricks-and-sticks home has walls that are 6” to 8” thick and they’re built on concrete slabs or conditioned crawl spaces.  A trailer is literally floating in space with cold or hot air circulating around it at all times - not an easy problem to solve. 


Each of these components are critically important when choosing the proper 4-season trailer. We’ll start with the most important factor in maintaining year-round comfort: insulation.

Insulation Design

How effective are the walls, floor and ceiling barriers in protecting the inside temperatures from the outside temps?  Or another way to say that - How well does the trailer “resist” heat transfer from outside to inside.  The more resistance, the less the heating or cooling systems have to work to keep that inside a comfortable temperature.  This concept of resistance is the key here.   In fact, Insulation is measured in what is known as R-value, with the “R” being resistance.  R-value is the measure of resistance to heat flow through a given thickness of material.  


And there are several types of insulation. However, in my opinion, when it comes to a travel trailer, inch-for-inch, closed cell rigid foam insulation is the best.  The reason I like rigid insulation is because it offers one of the best R-values, is lightweight, and completely waterproof.  I’ve seen countless insulation designs, all with their own self-acclaimed benefits and yes, there’s lots of good options.  


So, R-value is important, and is where the travel trailer industry puts most of its attention - after all, it’s easy to understand and is backed up by the R-Value stamped on the insulation used.  But it's just one of the key factors that determine the effectiveness of insulation material.  


Insulation must work in tandem with many other systems as a support mechanism to resist heat transfer.  Insulation is a great resistor to thermal transfer, but there are weak-spots throughout the design of the outside wall.   Areas where insulation is not able to be installed creates a tremendous weak point.  Areas such as structural studs, window frames, and hatch compartments create opportunities for heat to easily move from out to in.  Every one of these examples represents a direct heat transfer mechanism where the temperature outside easily makes its way inside.  


To resist that heat transfer, we need what’s called a thermal break to stop that flow of heat.  

Thermal Break

A thermal break is really just an energy dam (think resisting flow).   In a travel trailer wall, a thermal break is an element of low thermal conductivity, such as insulation discussed above (really good at resisting).  It’s anything placed in between the wall’s support structure and the interior to prevent the flow of heat or cold.  Another way to think of a thermal break is it is why you’d use potholders to pick up a hot plate from the oven.  It resists heat.  In more technical terms, it’s something that inhibits the heat or cold from two closely aligned materials from transferring energy from one object to another.  But too often in travel-trailer design, the idea of thermal break becomes an afterthought, a mere “foot-save.”


I highly recommend you pay particular attention to the concept of thermal break.  It’s for this very reason that published R-Values for travel trailers mean next to nothing.  If wood or metal studs are used, what is protecting the interior from that very susceptible stud location where there is effectively no insulation?  It doesn’t matter how much insulation you put in a wall if a metal stud is a thermal highway from inside to outside every 12” or so.


Travel trailer manufacturers tout high R-Values as a sales tool with very little real-world consideration to how it actually performs.  After all, that’s what matters most.    


An ideal scenario would be to completely separate the structural system from the insulation system -- like a Russian Doll.  The structural system being on the outside and the insulation being on the inside.  This is extremely difficult to accomplish when you’re working with only a couple inches of wall space. 


As you can see, the devil of luxurious design is in the details.  Using as many tools and techniques to break the interior environment from outside is what it’s all about. 

Freeze Protection of Critical Systems


The successes of experiencing very hot or cold climates in a travel trailer is measured by comfort.  Comfort is the ultimate goal, and countless design concepts, building materials, technology and equipment are working in tandem to support the cause.  In extreme temperatures, the functionality of those comfort-driven appliances become absolutely necessary.  The failure of one critical system would require immediate attention and a potential change of plans.  The protection of on-board equipment becomes extremely important.  


It’s rather obvious why not letting the inside of a travel trailer freeze is important.  You’d think that most traditional travel trailers would be freeze protected, but you may be surprised to learn that most camping trailer’s water and sensitive equipment systems are not designed to be freeze protected.  Most trailers we see on the road have many of their fresh and waste water valves exposed below the chassis.  This doesn’t work for sub-freezing climates.  Water expands when frozen, and a pipe or tank holding liquids can not freeze.   When it does, damage occurs  --  sometimes significant damage.  And believe me, a ruptured waste water tank that has frozen solid sounds (and smells) as bad and emotionally disturbing as you can imagine. 


So, industry engineers concoct solutions that prevent travel trailers from freezing.  These semi-solutions include heat pads on tanks (very limited energy hogs), extra fiberglass insulation (not solving the real problem), and complex heating systems with tons of capacity (over compensating for a poorly designed frame.)  The issue is, these are all just putting Band-aids on the issue.  Unfortunately, the designer paid little or no attention to thermal insulation design as a whole and was required by a marketing or sales team to pump out a list of features. 


Beautiful design just feels right and works for the user.  It’s easy.  The more I discover engineering, I’m finding that same feeling.  Great engineering is simple and works naturally.  Great engineering uses several layers of earth’s natural forces together to create an almost magical result.   What I’ve found to be the best solution is both simple and elegant to protect critical systems, it’s called a conditioned basement.  


A conditioned basement is a compartment below the main floor of the trailer.  It’s a space that’s just big enough to house all the electrical equipment, water tanks, and critical systems.  In a traditional home this would be considered somewhat of a crawl space -- which is a conditioned basement if it has insulation on all exposed sides.  When the heat source for the travel trailer is located in that conditioned basement space it draws air from the main space down into the basement.  If the air in your unit is warm, so is the air in the basement.  This naturally keeps all critical systems and equipment at the proper temperatures, too.


Poorly constructed trailers are built from wood, fiberglass and plastic compounds.  Well-built trailers are made from metal, including the floor, ceiling and floors.  A metal floor is a wonderful addition to the conditioned basement design.  The floor and joists act as radiator fins and retain heat.  After all, metal is a wonderful conductor of heat.  This results in a passive warm floor system.  As a bonus, the floor is only as warm as how warm the air is inside the unit.  It’s always perfectly in sync.  Not only does this basement design keep the floor warm, the conditioned space below the raised floor maintains a climate-controlled area for all the water systems and tanks, and temperature-sensitive electronics.  


When it comes to freeze protection, the value of a conditioned basement cannot be understated and becomes the basis for all design decisions going forward.  This is by far the best way to not only protect your systems, but it also provides a wonderful warm floor for the occupants.  My recommendation is to go with an all-aluminum trailer that circulates the air from the living space into a conditioned basement.

Dealing with Heat Loss


Now we get to the part of 4-season design where the current travel trailer industry excels.   Manufacturers have seemingly accepted the poor performance standards of the travel trailer shell -- the same way it has been built for generations.  With this acceptance comes the push for more powerful heating, cooling and air-conditioning (HVAC) systems to make up for the extreme heat loss.   


Suppliers of this vital  equipment have been competing for years on bigger air-conditioners, more powerful furnace systems, and highly complex heat exchangers.  These supporting HVAC components are what add the heat back into the unit when the shell isn’t able to resist the heat loss.  Unfortunately, this naturally becomes extremely inefficient because each one of those appliances takes a ton of power -- electricity or fuel.  Take a look at that air-conditioner or heater, there’s a sticker that measures BTUs.  That’s basically how powerful the appliances are.  The higher the BTUs, the more electricity or gas it will consume.  But what is a BTU?  What does it stand for? And what does it mean? 


Basically, BTU’s measures thermal energy.  Since the late 1800s it has become one of the most common units of classification in heating/cooling appliances.  In a nutshell, it is the energy needed to heat or cool a pound of water 1 degree Fahrenheit at sea level.  Shell design is also able to be measured in terms of BTU heat loss.  The more BTUs, the more capable an appliance is in raising or lowering a temperature.  More BTUs is better. 


Nevertheless, a higher BTU rated travel trailer does absolutely nothing with an inefficient shell design without any thermal break.  I’ve traveled in spaces where it didn’t matter how powerful the furnace was, or the additional space heaters I had because a poorly designed shell will destroy any cooling or heating source.  You can’t point to any one factor that will make-or-break a well designed shell.  There’s hundreds of tiny critical design decisions all working in tandem.

Windows, Doors & Hatch Design

Windows, doors and hatches are typically the most vulnerable sources for heat loss.  Uninterrupted insulation is by far the most successful method of protecting a travel trailer from the outside elements.   When that insulation is interrupted by any window or door, there is an opportunity for heat loss.  It’s because of this that trailer companies for 4-season units often minimize the number of windows and doors to the exterior.  Unfortunately, this is counterproductive to the ultimate goal of appreciating the great outdoors.  It is difficult to enjoy nature when you feel like you’re in a submarine with tiny portholes.  So extra care needs to be taken to ensure  the windows and doors offer outstanding protection from the elements.  


Doors and windows are also the points where water intrusion is most common in the shell design.  Techniques to increase resistant hatches include automotive quality double D-seal doors, drip rails, along with weep holes and channels for water to escape.  These details are no small feat to create a 4-season capable shell.  


The same pretty much goes for doors as hatches.  The quality of latches is also important.  They should be weather-resistant materials and, of course, water tight.  Hatches should be insulated with at least 2” of rigid closed-cell insulation being desirable.  The latches also need to be designed to work in very cold weather.   I’ve been traveling many times in travel trailers not designed for freezing temperatures, when I find unable to open an exterior compartment due to a latch being frozen shut.  SImple stuff, but it all has to work.  


When it comes to windows, don’t settle for anything less than dual pane if you plan to travel to hot or cold climates.  I also recommend UV tinting to reduce the radiant heat from the sun.  One might think the windows might be the greatest culprits to hot or cold loss, but they’re not. The trailers entire envelope, which includes the walls, ceiling and frame are where the game of temperature control is won or lost.


Frame, Ceiling & Wall Construction

The single most susceptible component of heat loss throughout the interior of a travel trailer are the components of the chassis and frame design.  These collective components are called the “trailer envelope.”  Think back to thermal breaks, which are the direct metal-to-metal connections. These are the points of greatest energy transfer from in to out, and out to in.  A poorly designed and constructed shell envelope is where the most energy is wasted.  Radiating heat from outside and heat transfer from points where studs meet inside and outside walls.  A thermal break is absolutely necessary.  


The exterior color of the travel trailer also has a great deal to do with radiating heat away from the interior space.  A dark colored exterior will absorb and hold radiant heat from the sun, whereas a lighter color or silver will reflect it.  Unlike solar panels where absorbing sun is highly advantageous, the exterior surface of the travel trailer should do the exact opposite.  Light, reflective exterior colors will ensure the skin does not get unreasonably hot in direct sun.  


If you can find a trailer that uses air as an insulation tool, all the better.  In our discussions about insulation and the transfer of heat, one material is widely not discussed, and for good reason.  One of the best ways to ensure a hot exterior wall does not radiate heat or cold into the interior wall is to physically separate that wall so that it does not touch the interior wall.   Ever heard how a vacuum is the best insulator?  Well, air is a very close second.  As you can imagine, this is no simple engineering exercise.  A travel trailer wall has limited space to offset the wall to create an air gap, let alone the structural components needed to support that wall standing vertical.  Air gaps are highly beneficial to prevent heat transferring to the inside walls, ceilings and floors.  


Whatever the case, particular attention must be given to the outermost envelope of the travel trailer.  After all, this point is where the trailer meets the environment and is most susceptible to hot and cold weather. 

On-Grid vs. Off-Grid Use in 4-Season Environments


The difference between on- and off-grid use is fairly simple.  On-grid means you’re connected to, and reliant on, the city's electrical, water and waste services.  Off-grid means you are not connected to, nor reliant on a utility grid and may manage your own resources, no matter where or when you travel.  


There are many benefits to on-grid living, the most obvious being you’d be connected to an inexhaustible supply of electricity for heat and air conditioning.  If you’re going to spend a lot of time in subfreezing temperatures, then it will be much simpler to use electricity to heat your home, and life doesn’t get much easier than plugging into a 110v power outlet.  But as always, there are tradeoffs:  neighbors, noise, and interruptions.  Or what about feeling the pull of that electrical chord - ever feel like a ball and chain, keeping you from traveling to off-grid locations?  When plugged into the grid, your trailer should operate all of it’s electrical systems without a care in the world, and you can run an fairly unlimited amount of electrical systems, while charging the onboard batteries… until the power grid goes dark.  While seemingly luxurious, it’s a tremendous limitation.  


Off-grid is for those who want to experience freedom.   Along with this comes the unbridled adventures of the Great Outdoors, wherever their heart leads.  In this case, the travel trailer must first be self-contained, capable of storing enough supply for vital resources like fuel, energy and water.  Self contained means that you use what you take with you.   Once those resources are gone, your travels are over - time to turn around.   The key is extending those on-board resources as much as possible.  


In order to go off-grid for a longer period of time, you’ll need a robust renewable power source, such as solar or other sources of power generation, which leads us to our next topic.

Power Generation, Hot vs. Cool Environments

I believe that a luxury travel trailer was created out of a desire for ultimate freedom.  Off-grid travel is not just about traveling in remote environments.   The concept of off-grid provides the freedom to travel when and where you want, with as few limitations as possible.  


A luxury travel trailer is intended to be used all year long and should not be limited by summer or winter months when temperatures venture outside of ideal comfort.  So naturally, travel trailers should be designed to go to both summer and winter environments. Of course, these two seasons have very different requirements of what is possible to travel successfully. For example, the amount of sun available during the winter months is significantly less than summer. Depending on where and when you travel, there may be very little to no sun at all.  

 

In the summer we are blessed with a wonderful natural resource from the sun to generate a seemingly endless supply of natural energy. This is particularly useful for high power demand equipment that helps keep the inside cool such as air conditioners. We believe travel trailers should be designed to leverage this resource and run the air conditioning system from solar power.  While most trailers will run an air conditioner with a generator, this is a terrible primary source of power and will consume a tremendous amount of fuel.  To the opposite degree, the amount of sun available in the winter is significantly less with very different impacts. With just a fraction of available solar energy than during the summer, this significantly changes where a trailer may gain energy to power the necessary heating systems during winter months.

 

Due to lack of solar in the winter, travel trailers must rely on alternative fuel sources to provide necessary energy to keep the inside warm. Propane is common and regularly used as a fuel source for travel trailers. The better the insulation and thermal shell design the less heat that’s required, and in turn, the less amount of propane that is consumed. When coupled with a large array of solar panels and minimal sun exposure, a combination of gas and electric heat is a winning approach.   


In order to make this a reality, the energy capacity in the battery system must be as large as possible.  This gives you the ability to store power from the sun and use it later when that solar power  is not available.  The bigger the battery capacity, the longer you will be able to run these critical components.  I recommend a minimum 10 kWh battery bank for short-term travel.  If you are looking to travel for weeks, if not months at time in extreme temperatures, I recommend a battery system as big as possible.  

 

Additional power generation sources such as propane or gas generators are able to create redundant sources of power when solar is not available. These redundant power sources are designed to recharge your battery system without solar power.  One additional and often overlooked resource is the power of the engine in the tow vehicle itself. There are high voltage alternators designed to work in tandem with advanced battery equipment in the travel trailer so that the tow vehicle is able to recharge the entire trailer energy pack in a matter of hours. This allows quick recharge times during winter months and the convenience of being able to not only charge but run high demand power systems to keep the interior conditioned at all times.

Redundancy

If you were an astronaut in a space capsule 100,000 miles from earth, then you’d be glad there were two sources of oxygen.  Check that -- it would be critical to your survival and safe return to earth!  If you’re traveling in a travel trailer, off-grid, in 20˚ temps, 100 miles from mechanical support services it might not  be an issue of life and death, but I guarantee you’ll sleep better knowing you had two sources of heat just in case one ran out of fuel, or electricity, or failed altogether.


While we may not yet be traveling to space any time soon in our Travel-Trailers, 4-season use is increasingly more challenging to ensure all things go according to plan.  No matter how thoughtful a travel-trailer is designed, Murphy's law is always a very real possibility.  If you’re traveling in freezing temperatures and are reliant on one heat source, it will inevitably fail when you need it most.


The simple concept of having a backup ready and waiting is one of the most important factors in true 4-season capable design and planning.  It’s critical to have two sources of power generation, two sources of heat or cooling.  Redundancy means we are always planning for something to go wrong.  When it does, we get to continue along with our backup plan not because something went wrong, but because it was part of the plan in the very beginning.   Being reliant on one critical system is an incredible risk.  When two is one and one is none, having multiple backup plans in place will allow you to go further and stay longer in extreme environments.  


The design of a luxury travel trailer must carefully consider the concept of redundancy.  Multiple sources of power, heat, and cooling are vital when pushing the limits of travel. 

Conclusion: The Ideal Scenario

So, what’s the ideal experience for 4-season, off-grid-capable trailer setup?  A successful Luxury Travel Trailer design will include these options built-in and seamlessly integrated:


Shell Design

  • Thoughtfully designed & engineered thermal shell
  • 100% closed cell rigid foam insulation used
  • Thermal breaks in the walls with a true air gap
  • Seamless aluminum roof for water protection. 
  • Large windows, skylights and ceiling fans for natural ventilation and connection with the outdoors. 
  • Dual-pane windows and patio doors


Interior Design

  • Conditioned basement and subfloor heating system
  • Aluminum flooring and floor joists for passive warm-floor
  • All water systems located in a conditioned basement
  • Easy access to all systems for convenient servicing


Energy and Equipment

  • Large lithium battery capacity over 10 kWh
  • Solar panels, with at least 1200 watts
  • Tankless water heater capable of operating in freezing temperatures
  • An Air-Conditioning system that is capable of running from solar power
  • On-board backup generator, tow vehicle alternator, and other sources of redundant power generation
  • Powerful and efficient furnace and air-conditioning units
  • Redundant systems for heating and cooling