Best Insulation for Trailer

More and more people are becoming interested in turning their RVs and campers into perfect little traveling condos, with all the necessary features that will make their traveling adventures smooth and pleasant. But where most people make mistake is putting everything into the trailer design, forgetting about its functionality and something more important - and that’s insulation.

Trailer insulation is actually the key aspect of any DIY trailer conversion because that’s the thing that will make sure you won’t freeze to death during winter months travels, or boil from heat when the temperatures go high in the summer time. So we prepared a thorough guideline as to what to pay attention to when insulating your RV, camper, or cargo trailer.

All you need to know about insulating a trailer

The very first thing you should know about insulating a trailer is you absolutely should do it, no matter what you are planning to do with it. Insulation is what keeps temperature regulated all the time, without it the interior of the trailer will always be exposed to outside conditions through different levels of heat transfer. So whatever insulation you install, whatever type or the amount of it it's better than having none.

But before we go any further and engage in steps to insulate a trailer, here is what you need to know about how insulation actually works.

Heat transfer

There are three forms of heat transfer - radiation, convection, and conduction, and all of them affect the inside temperature of a trailer. The easiest way to explain radiation is through the sun - when exposed to direct sunlight the trailer will get warm. Convection is a heat transfer through the air - when the walls of the trailer get warm because of the sun, the air inside becomes warm as well. And conduction is heat transfer from one material to another - it is responsible for transferring the temperature of the outer walls to the inner walls of the trailer.

Another important thing regarding heat transfer is the type and thickness of insulation material. Insulation for a cargo trailer, but also for Rv and camper can be made from various materials, and they are all different in the aspect of allowing heat transfer. They all have different densities, some of them have air pockets, and not all of them are suitable for all climates and all trailers.

Thermal bridging

Then there’s the matter of thermal bridging. In case not all aspects of your vehicle are fully insulated, like for example the beams while the walls are, then it may happen that the heat or the cold from the outside passes into the interior through those beams. That’s called thermal bridging, and you can avoid it or reduce it by making sure all parts of the trailer are covered with some sort of insulation material.


Every insulation material in the market - spray foam, rockwool, bubble wrap, rigid board, fiberglass, prodex total, and all others has a specific R-value that indicates how exactly is the concrete material resistant to heat transfer. The higher the R-value is, the better. But bear in mind you don’t need the highest R-value for all the climates and all locations.

RV - Camper - Cargo trailer Insulation

If you are wondering how to insulate a cargo trailer, or any other trailer type here are the steps you need to take:

Insulate windows

No matter if it is cargo trailer insulation or insulation of RV and camper, you need to start with windows and check their state. Windows are generally the weakest link when insulation is in place, mostly because most trailers have single-pane windows, and they are not designed to keep the temperature in place. So there are two options - either to replace the existing single-pane windows with double or triple-pane, or to cover windows with bubble wrap that will allow the light inside, but prevent a certain amount the heat from leaving the interior, or the cold to enter the trailer.

Seal doors

The second step includes establishing in what condition are the RV doors, whether or not they are dirt-tight. The more expensive solution, if you need one, is to install an energy-efficient door, and the cheaper version is to hang the thermal curtain on the outside, as well as a door snake to keep the air leak.

Cover vents

What most people miss in cargo trailer wall insulation are vents. It may happen that you insulated walls and floors, and you checked doors and windows, and the air is still leaking from somewhere. Those are the vents that can be covered with a vent cushion. The better option is a non-reflective cushion which is a bit more expensive but much more effective.

Install skirting

It may sound silly, and it definitely looks funny, but RV skirting is a very good solution when it comes to keeping the cold or extensive heat out of your trailer. Skirting actually implies a piece of fabric you can wrap around the bottom of your trailer and leave to hang all to the ground. It prevents mostly the outdoor cold from entering the interior of the vehicle from underneath.

Trailer floor and walls insulation

The main aspect of RV insulation is the walls and the floor of the vehicle, which is logical given they are the base of the trailer. In most cases, campers and RVs come with a certain amount of insulation, but that simply won’t be enough protection if you plan to use the trailer for travels and as a living space. That’s why you should think about adding more insulation.

If you want to achieve consistent temperature maintenance you should think about fiberglass or spray insulation foam. Fiberglass is very reliable as a trailer insulation material, and spray foam is great for plugging air leaks in the walls or around pipes, etc.

But before you decide to do this part, and especially if you are thinking of doing it alone, make sure to at least consult with a professional about the whole process, and make sure to check if your vehicle will stay in warranty after you add more insulation.

Insulating camper shell

There are many types of insulation you can use for a camper shell, some of them are more or less effective and more or less difficult to install. So when you consider all the aspects the best insulation for a camper can be one of these four options:

Styrofoam - it is mostly used because of its light weight and because it is very easy to install. However, it has a big flaw and that’s not-so-good moisture and condensation barrier. Also, this material comes with a lower R-value.

Spray foam - spray insulation is a bit messy and takes time, as well as some extra sets of hand, but it is an effective insulation option. Especially because of its ability to fill all the small gaps and air leaks in the trailer.

Rockwool - this insulation has a pretty high R-value and great density, but it is mostly used in hot climates. It is more expensive than fiberglass and very similar to it, but less expensive than spray foam. Its main problem is that it doesn’t create air barriers.

Fiberglass - as the most often used insulation material for trailers fiberglass is very easy to find and install. What you need to bear in mind with fiberglass is it cannot come in contact with your skin, so it needs to be covered after you insulate the RV with it, and you need to protect your skin when working with it.

Rockwool VS Spray foam

The truth is both of these insulation materials have their benefits as they do have flaws. And both of them are frequently used as insulation for RV walls. So it’s really just a matter of personal opinion whether you should use one or another. Here are all the facts:

  • Rockwool is a less expensive insulation option than spray foam
  • Spray foam is a better option for keeping the moisture out of the trailer
  • Because of its density Rockwool provides better sound insulation
  • Rockwool is not made of any chemicals, it is actually a rock-based mineral
  • Rockwool is vapor permeable so it can get wet; when wet it can’t proved adequate insulation
  • Unlike spray foam that should be applied by professionals, you can install rock wool by yourself
  • Rockwool doesn’t create an air barrier
  • Rockwool is the most effective in warm climates
  • Spray foam is a better option for floors and ceilings
  • Spray foam is more durable - it won’t become compressed or saved over time
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