A Guide To Insulating A Shipping Container​

Do you need to insulate your shipping container?

Modern shipping containers are designed to be highly durable, especially those constructed with corten steel. However, they are also designed to carry goods across the ocean. If you’re planning on using a shipping container as storage, an office, or even your home, you’ll need to consider comfort and practicalities.

Shipping containers can last many years as a comfortable space if designed efficiently. Making sure that it’s insulated properly is an important first step towards spending time in your container.

Benefits of container insulation

Temperature control

Shipping containers are made from steel which heats up quickly and cools down easily. In the UK this means that in the summer a shipping container can be unbearably hot, while in winter it can be close to freezing. Adding insulation to a shipping container can help to control those fluctuations. It gives you a more consistent temperature year-round.

Prevents condensation

Temperature differences between the inside and outside of the container can result in condensation forming in air pockets. This moisture could then damage the internal fittings, furniture, or anything stored in your shipping container. In extreme cases it could also cause health issues if people are exposed to damp for long periods of time.

Insulation fills these small air pockets and helps to stop condensation forming.

Comfort and usability

If you’re only using your container for storage then you might not mind how comfortable it is in there. However, ensuring it’s properly insulated will make your shipping container enjoyable year round. This is especially important if you’re converting into a home or office space.

Energy efficiency

Reducing the extreme temperature differences inside a container can help to reduce any associated heating and cooling costs.

Many people add heating or air conditioning units to have more control over the temperature in their container. But the costs of running these can add up over time. Making sure that you’re container is well insulated will help to keep the temperature consistent across the year. This means your heating and cooling elements can work more efficiently and save you money!

Protecting contents

Insulation can help to prevent moisture damage inside your containers. If you’re not using this space regularly then you may not notice the warning signs of dampness. Using the correct insulation on your container can give you added peace of mind that your tools, stock or furniture will all stay in tip top condition.

Noise reduction

Steel is an excellent conductor of sound, so from your container you’ll be able to hear outside and outside will be able to hear you. The added insulation will soften any noise to make your time in the container more comfortable. This is ideal if you’re planning on using your container as a workshop or you’re near a road. You'll reduce the noise your neighbours hear and minimise how much you're disturbed.

Aesthetics

Insulating your shipping containers provides options for enhancing the look of your shipping container. Exterior wooden cladding offers a natural appearance while metal sheets are a modern option for the outside of a container. A living roof garden can help to insulate the shipping container roof while adding visual interest.

Interior vs Exterior Container Insulation

Interior insulation

Many types of insulation are best used inside of your shipping container. Interior insulation options can be cheaper and faster to install than exterior options. With many to choose from, interior shipping container insulation can be the best choice for anyone on a budget.

Interior insulation can reduce the interior width and height of your container. If you’re buying a smaller container or you have specific space requirements, you might be more limited by the interior insulation options.

It’s important to install interior shipping container insulation correctly to prevent thermal bridging. This is a major issue for steel structures. Any gap in the insulation can cause heat to escape, then condensation may form on the steel container. This can lead to damage, rust and mould forming.

Exterior insulation

If you can find the right ways to insulate a shipping container from the outside​, there are a couple of advantages. The main one is that it prevents you from having to reduce the container’s interior space. It also offers additional exterior protection from rust and condensation.

Exterior shipping container insulation does normally have higher costs. Your container may be weatherproof already, but to be effective your insulated cladding needs to be weatherproof too. For some people, the aesthetics are an issue - exterior insulation options don’t always look as nice!

You can opt for both interior and exterior insulation: some container home conversions combine thin spray foam insulation inside with exterior cladding.

Best Types of Insulation for Shipping Containers

The best insulation for your shipping container will depend on your budget, your usage, and the condition of the container.

Note: If you’re planning on moving into your shipping container then it must meet certain building regulations to be classed as ‘livable’. In this case, insulation must be of a certain standard for heat retention and fire safety.

Foil insulation

Foil insulation is usually a roll or sheet of material with foil on both sides, though there are various types of foil insulation. The foil reflects the radiant heat from both inside and outside the container. This keeps the temperature more stable.

The flexibility and cheaper cost of foil insulation makes it a good choice for those on a budget. You also don’t need any specialist tools to install it. However, foil insulation isn’t usually enough to fully insulate a space on its own. You may need to combine foil insulation with another container insulation solution.

Another consideration for foil insulation is that there needs to be a small air gap around the insulation. This creates a thin air pocket that will add another layer of insulation, help to reduce condensation, and keep air circulating.

Fibreglass

Fibreglass is made up of extremely fine glass fibres that have been woven together in the form of rolls, batts, or loose-fill. It is a popular choice because it is cost effective and easy to install. However, moisture can also become trapped in fibreglass which can cause damp and mildew problems. This means fibreglass may not be the best option for a shipping container in the UK.

Rigid foam boards

Foam boards are lightweight, easy to cut, and have a high insulating value. There are various options for the material that these boards are made of, making them extremely versatile. Other insulations may be more cost effective, but foam boards are durable and long lasting.

You need to carefully cut and install these boards to avoid gaps. Even then, the corrugated steel of a shipping container can leave air pockets which can then trap moisture.

Mineral wool

Mineral wool can be made from a variety of natural materials such as stone, silica, or glass. The materials are then melted at high temperatures, spun into thin fibres, and fabricated into rolls or batts.

It is naturally fire-resistant, moisture wicking, and sound-dampening. This makes it a popular choice for living spaces, even though it is more expensive than other insulation options.

Mineral wool on its own may not be enough to prevent moisture issues in shipping containers. It can be combined with other insulation options or you may add a vapour barrier to help prevent condensation.

Spray foam insulation

Spray foam insulation is a liquid form of polyurethane. When sprayed into a space it expands and then dries, creating an insulating layer. It requires professional installation but has many benefits that make it an excellent choice for insulating shipping containers.

The foam expands to fill in any gaps or uneven surfaces which helps to stop the issue caused by a shipping container’s corrugated walls. Spray foam dries into a seamless, airtight surface so will reduce air leakage. The spray is applied directly to the shipping container so it helps to prevent condensation forming.

However, spray foam is not vapour permeable and so existing moisture cannot escape through the insulation layer. To combat this, check your shipping container is free of leaks regularly. You should also consider installing moisture traps to contain moisture from living or workspaces.

Exterior Cladding

Many of the above insulation options can also be used on the outside of your shipping container. This can either be to increase the amount of insulation or as a space-saving alternative to interior insulation. However, exterior shipping container insulation must be protected from the elements to work efficiently. This can look like adding a waterproof layer followed by cladding.

Cladding the exterior of your shipping container can be a good option if you’re looking for a certain aesthetic. There are options for treated wooden cladding, metal sheeting, or fibre cement. This might be a priority for people who are converting their containers into homes. However, it can work out to be pretty expensive depending on the materials you have chosen.

Eco-Friendly Options

Sheep’s wool, cellulose, cork, wood fibre, and even recycled clothing can all be used as insulation. These are all natural, recycled, or minimally processed which are all better for the environment. They’re also breathable and safe to handle, but can be significantly more expensive than other insulation options. However, many of these materials are also less efficient at reducing moisture, so may be better suited to interior walls rather than directly next to steel.

Adding a living roof garden can be an excellent way to further insulate the roof of your shipping container. It can also add height, visual interest, and nature to a space that can sometimes be forgotten.

You should take into consideration that this can add significant weight to the roof of the container. It may also increase the risk of moisture accumulating. Make sure to waterproof the roof, add drainage, and consider adding guttering to avoid this.

Don’t Forget About Ventilation!

Ventilation allows air to move through and out of a space, taking excess heat and moisture with it. Stagnant air can also accelerate rust or corrosion, create ideal conditions for mould, or allow the buildup of odours. This makes ventilation an essential part of converting a shipping container.

The ventilation you choose can influence your insulation choice and vice versa, so it is essential to consider both at this stage. There are passive ventilation options which are usually cheaper but less effective. Active ventilation is generally more expensive and requires electricity. However these options are significantly better for circulating air, especially in habitable spaces or workspaces.

Passive Ventilation

Ventilation grilles such as louvered vents or slatted grilles are metal or plastic pieces that are mounted and sealed to the wall of the shipping container. They are cost effective and easy to install. Further ventilation can be added by installing two vents across from each other to create cross-flow ventilation. However, this method relies on outside air flow as there is no active air movement.

Roof turbine ventilators (also known as whirlybirds) are rotating heads mounted on the roof of a shipping container. The wind then rotates this turbine which pulls out hot air from the container.

The turbines move significantly more air than vents, however they require cutting a hole into the roof of the container. This needs to be sealed so there are no leaks. Roof turbine ventilators are best used in combination with grills and vents, but they still rely on wind power so can be less effective on calm days.

Active Ventilation

Exhaust fans are mounted in the walls or ceiling of your shipping container. They actively draw the air from inside the container and eject it, allowing fresh air to circulate.

While they do require electricity, exhaust fans can be relatively cheap to run. There are even solar powered fans that you can use through the summer. However, there are no climate control options with an exhaust fan. They are best used alongside passive ventilation options.

Air conditioning and HVAC systems offer a fully climate controlled option. This can be better for spaces where you’ll be living or working for a longer period of time. These systems give you full control over temperature and humidity in your shipping container, but they are the most expensive option.

HVACs need a consistent power source and can require professional installation. Ongoing maintenance and power costs can add up over time, but for some people the full climate control can be worth the extra costs.

How To Insulate Your Shipping Container

1. Prepare the container.
   1. Clean
   2. Treat rust
   3. Fill gaps
2. Decide on your insulation (and ventilation) options based on usage and budget
3. Build the internal frame
4. Fit insulation
5. Install vapor barrier

Prepare Your Container

The first step to insulating your shipping container is preparing it. Make sure to clean both the inside and the outside of the container thoroughly. Check for any patches of rust, gaps in the welding, cracks, or leaking. You will need to treat or fill there before you can start putting insulation in the container.

Choose Your Insulation

Various factors will you final decision on the best shipping container insulation for your project. Thinking about how you'll use the container and how much you want to spend can help narrow it down.

You should consider ventilation at this point as well. Choosing ventilation that needs electricity or a hole cutting can be easier while you’re adding insulation, rather than after it’s been installed.

Build the Internal Frame

The internal frame of the shipping container gives you both the layout of your space and a space to fit your insulation. You'll need to insulate the floor and ceiling too. You can either build the frame outside and then bring it into the container, or build it insitu.

Remember: don’t drill directly into the walls of the container. Adding holes or damaging the steel creates a weak point that could potentially let in moisture or develop rust. Instead, use quality adhesives to attach your frame to the container walls and only drill the wood itself.

Fit Your Insulation & Vapour Barrier

Each installation option will have different fitting instructions, and you should follow the manufacturer's instructions. Some materials (such as fibreglass) may require PPE like masks or gloves to avoid irritation.

The vapour barrier is a thin layer of plastic sheeting that is attached to the internal side of the insulation. It stops moisture inside the container getting into the insulation layer, which can cause problems with dampness. Make sure to overlap the edges of the sheeting and tape it down to create an airtight seal.

Finally, you can add your internal walls and panelling. Plywood or plasterboard can be added directly to the wooden frame to cover the insulation and vapour barrier.

How Much Does It Cost To Insulate a Shipping Container​?

There are so many different factors that go into the cost of insulating a shipping container. There isn’t just the cost of the insulation itself; there’s rust treatment, timber for the wooden frame, tools, screws, and plenty of cups of tea! The cost can also be determined by what you’re using the space for. Converting a shipping container into a habitable space can require better quality materials along with budgeting for any professional services.

You can buy a kit for insulating a shipping container for about £200, but this is the most basic level of insulation that will only be suitable if you’re using the container for short-term storage. For long term use as a home, office, or workshop then you’ll need to consider a more custom solution.

On a Budget? The Cheapest Ways to Insulate a Shipping Container

If your budget is tight, here are some cheaper DIY methods for insulating a shipping container. They won’t all be as effective as investing in more costly methods, but will allow you to create a comfortable space inside your shipping container.

• Consider only partially insulating your container or doing it in stages to maintain quality over quantity. Focus on insulating the roof first as this is where most heat will be lost and gained.
• Add anti-condensation paint coatings or reflective barriers. These are specially designed to prevent moisture from building up in enclosed spaces.
• Use recycled insulation boards or offcuts from builders’ merchants.
• Sometimes it’s worth hiring a professional. If doing it yourself means doing it again (and again) then it can be more cost effective to hire someone.

Tip: Safety should always come first, whatever your budget. Make sure you avoid using any flammable materials when insulating near electrical wiring.

Insulating a shipping container ensures you have a usable, comfortable space for years to come. There are so many different insulation options to choose from, so it can be overwhelming when you’re still in the planning stage.

Just remember to keep the end use of your container in mind, make sure you have a realistic budget, and a sustainable timeframe to work in. By planning ahead and making these decisions before you start, you’ll have a container that lasts for years to come.