How to Build a Four-Season Airstream

It’s been getting into the teens overnight, and everything but our tiny Airstream home is frozen solid. We’re definitely doing this snowbird thing all wrong.

It was always our intention to move South each Winter, but we haven’t managed that yet. Last year, we ended up overwintering in Maryland after returning for some family events, and stayed so we could finish up some renovations, adopt a new dog, and frankly, because moving is expensive and we didn’t have anywhere else we needed to be. This year, we have a baby on the way, so we’re here for the duration to be close to our midwives.

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Building an Airstream for Winter Living

Factory Airstreams are not four season trailers. They do OK in the Summer (provided you have hookups or a generator to crank the A/C), and the Spring and Fall, but a cold Winter in a factory Airstream can be miserable. The aluminum ribs conduct heat straight through the walls. The furnace gobbles up tank after tank of propane even in relatively mild conditions, and in colder climates, struggles to keep your living space reasonably warm and your water tanks liquid. Once your tanks are frozen, you really are camping, since there’s no showers, no dishes, and no washing your hands. Any moisture in the air from cooking or breathing condenses on the cold walls, runs down to the floor, and can start mold growth.

If you’re re-building a trailer from the ground up, though, it doesn’t take much to build an Airstream that can be comfortable throughout the Winter. Here’s a list of our modifications that help keep us cozy throughout the colder months.

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Insulation

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We used rockwool insulation in our walls and in the belly pan, with reflectix against the outer skin over the upper half of our rig. I couldn’t tell you whether the reflectix makes any difference in the summer, but it certainly doesn’t hurt anything.

Whether you choose fiberglass, Rockwool, or spray foam in the walls won’t make a huge difference in R-value, since you only have an inch and a half or so to work with. What will make a big difference is making sure you install it properly. Convection is your enemy inside the walls and belly pan, so avoiding voids is critical. Spray foam is obviously your best bet for avoiding voids, but it has its downsides. I really like how rockwool made a nice tight assembly when I installed it. I also liked how I could buy it at the hardware store and it didn’t require the assistance of a professional.

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I’ve seen folks cut up pre-formed foam panels for their insulation, and I have to say, I’m not a fan. Pre-formed panels don’t fully fill the space in the wall. Air space around the panels allows air to flow inside of the wall, bypassing the insulation entirely. I suggest using either spray foam or batt insulation.

See our insulation product picks here, and see the wall insulation here and belly pan insulation here.

Thermal Breaks

An Airstream is constructed with an interior and exterior aluminum skin, held together with aluminum ribs. If the ribs are touching the skin on both sides, heat will conduct straight through the ribs, bypassing the insulation. This is also true of heat conducting from the wooden subfloor, through the frame, to the belly pan.

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Adding a thin layer of insulation somewhere in this assembly adds some resistance to the flow of heat through the walls and the floor, which improves the insulation performance of the assembly. I don’t have any numbers on it yet, but anecdotally it’s working very well for us, and I would recommend incorporating thermal breaks where you can in your renovation.

See how we installed thermal breaks between the ribs and interior skins here. See how we used reflectix on the underside of the subfloor to add a thermal break here.

Heat Sources

Most Airstreams come with a propane furnace installed. We pulled ours out and did not replace it. We have nothing against propane furnaces, except that they’re loud and consume tons of propane and a moderate amount of electricity. We just didn’t want to be dependent on propane for heating, and we needed that space for the dishwasher.

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For when we have hookups, we have two electric heaters. First, our Coleman Mach 8 Cub has the heat strip installed. It’s advertised only as a “chill chaser,” but it’s done a good job of keeping our Airstream warm until the weather gets into the teens (F) or below. As a supplemental heat source, and because we can’t run the heat strip without tripping a 15A outlet, we also carry a small 900/1500 watt countertop space heater.

For off-grid heating, supplemental heat, or (let’s be honest) any excuse we get to make a fire, we have a Hobbit wood stove installed with the RV/Bus flue kit from Tiny Wood Stove. The wood stove gives us a powerful, dry heat source that requires zero electricity, and is better to watch in the evenings than TV. We find that the Hobbit, which is about the same size as the Dwarf 4kW from Tiny Wood Stove, is a bit too much to burn without opening windows until the outside temp is well into the 50s (F). It really hits its stride below freezing, and we’re not sure we could live without it when it hits zero degrees.

See our Coleman Mach 8 Cub installation here.

See our wood stove installation here.

Dehumidification

Moist air in a small space is a problem during the Winter. No matter what you do, the windows and walls will be cold, and if the air is humid, water will condense on the walls and mold will grow. Even if you don’t use a catalytic heater or even cook inside your RV, the moisture you exhale can be enough to create a problem.

We don’t have space or electricity to spare for an electric dehumidifier, and as it turns out, we don’t need one. Dessicant dehumidifiers are available, but if you have a powerful, dry heat source like a wood stove, you have everything you need to dehumidify your rig.

When we see some condensation forming on our windows, we fire up the wood stove and crack open a roof vent above it. The wood stove gives us plenty of heat to spare, and the hot air escaping the top of our Airstream carries moisture with it. Running this way for an hour or so will clear up the condensation from the windows, and tells us it’s OK to close up the vent.

You don’t necessarily need a wood stove to dehumidify your space this way. Any sufficiently powerful dry heat source would work fine. As long as you have enough spare BTUs to lose some heat out the vent, and your heat source isn’t actively adding moisture to your air, you can dehumidify your rig in the Winter without any additional gear.

Water Tanks

One of the most important factors in building a four-season trailer is how to keep your water tanks liquid. If your fresh tank or plumbing freezes, you can’t shower, wash dishes, or wash your hands after the bathroom. If your waste tanks or hose freezes, you can’t dump them.

We use an Air Head composting toilet (similar to the Nature’s Head), so we don’t have a black tank to worry about. But we do have gray tanks and a fresh tank to worry about.

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I installed 12V heating pads on both the fresh water tank and the primary gray water tank, and added Reflectix insulation to both. The two secondary gray tanks are emptied and valved off in below freezing conditions, since they don’t have heaters.

We found out last Winter that the suction line off our fresh tank is also susceptible to freezing even though the tank is heated, so we added 12V pipe heater to the suction line coming off the fresh tank as well. That would have been easier to do before installing the tank, but I do still have access to the side plumbing on the tank through a hole in the floor under the kitchen cabinets.

We keep our gray waste valve closed when winter camping, and only dump intermittently when it gets full, even when we have a dump hookup. This allows the heater to function properly (there needs to be water in the tank when the heater is on or the coil could burn out), and keeps the water in the plumbing manifold and the dump hose from freezing.

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Since heating pads would use up a good portion of our available solar energy off-grid, we wanted another option to keep our fresh water liquid for off-grid Winter camping. When I replaced the fresh water tank, I added a return line, which would allow me to dump hot water (from the PrecisionTemp RV-550 water heater) into my fresh tank. I hooked a cheap 12 volt thermostat with a longer sensor wire (dropped to the bottom of the tank through the fill tube) to a 12V solenoid valve to control the hot water dumping into my fresh tank. Using the thermostat, I’m able to heat my entire fresh water system (plumbing included) with propane, and only as much energy as the water pump needs to kick on periodically. (While I was at it, I added a momentary switch, which allows me to prime the hot water before I take a shower or run the dishwasher without wasting any water.)

Keeping Yourself Sane

The hardest part of living in an RV in the Winter is keeping yourself sane. Sure, it’s perfectly comfortable in our Airstream, but it’s still only about 180 square feet. We built our home with the idea that the outdoors would be part of our living space. When it’s 10 degrees, we don’t spend a lot of time outside.

How best to manage that? Well, we’re still learning. Going out as much as possible seems to be the thing to do. Anyone have thoughts? Leave a comment below.