Best Ways To Insulate Your Shipping Container Home

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Whether placed in a cold, hot, harsh or moderate climate, insulating a shipping container home is the key to comfortable indoor temperature pertaining to the high conductivity of its metal envelope. Although it is an easy process, The array of options and lack of information can lead you to make some regrettable choices and long-term issues. This article will educate you about the dos, don’ts and available materials for insulation to enable you to make informed decisions.

Key points to note when insulating a shipping container are:

  1. Know the insulation standards as mentioned in the building code of your area
  2. Insulate the walls, roof and floor for effective results.
  3. Select insulation material based on these factors:
    • R-Value (Depends on your climate, surroundings and code)
    • Cost
    • Thickness (the area it will occupy of the limited width of your container)
    • Water, fire resistance, and vapour retardancy (Shipping containers are prone to condensation)
    • Installation Method

Where to insulate (roof, floor and walls)

As a shipping container is a metal box, it is very important to prevent any form of heat transfer through it to achieve an energy-efficient interior environment. Therefore, it is important to insulate all the faces of a shipping container home: The roof, floor and the walls

Exterior insulation:

Exterior insulation is the more recommended type of insulation in a shipping container home, as it solves two major issues, i.e. 

  1. It saves the limited space
  2. Prevents issues due to condensation.

However, it has two drawbacks

  1. It hides the industrial look of the container
  2. It needs good weatherproof cladding/ siding to protect it from the weather and moisture.
  3. Not all materials are weatherproof to endure the exterior environment.

Interior insulation:

This type of insulation is more protected from the harsh weather and covers the potentially toxic walls to live a healthy life. But it needs to be efficiently done, as it has to prevent heat from entering through the already hot metal wall. Following are the benefits of interior insulation.

  1. Safe from external weather, moisture etc.
  2. Creates provision to conceal the electrical and plumbing lines within.
  3. Acts as a barrier for any previously absorbed toxic gasses from releasing into the living environment.

Some issues to be considered in interior insulation is.

  1. Depending on the type of insulation, it may reduce the already limited space within a secure container home by 10-12 inches.
  2. The issue of condensation has to be considered before choosing the type of insulation.

Follow code for the required roof, wall and floor insulation

  • As shipping container homes are generally raised above the ground, the floor can also be a source of heat transfer. Thus, also insulate the floor.
  • Make sure to avoid any agents of thermal bridging. (Refer ‘How do shipping containers get hot?’)
  • The corners of Shipping containers can be tricky to insulate due to their weird shape and orientation because of the corrugations. Make sure to use spray foam to fill any potential voids.
  • If insulating using boards-
    •  First, insulate the floor till the edges, then add the wallboard on top of it. This workflow will ensure no voids or gaps for heat loss and create a closed insulated envelope.
    • Use the spray foam for windowsills to seal the joints between the boards to ensure complete sealing.
    • Use the foam boards judiciously as they are expensive. If you measure, cut and plan carefully, you can utilize all the cuttings to insulate the tricky corners and ceiling areas without wasting any material.
  • If insulating using batts-
    • Remember to fluff up the batts, as their R-value depends on the air gaps between the fibres. If the batts are compressed, their R-value will drop down significantly.
  • If insulating using Spray Foam-
    • Make sure to give each layer enough time to expand before spraying on the next layer. Not doing so could cause many issues in the future like Off-gassing, compromised vapour retardancy, lower R-value etc.
    • Hire a professional.

Selecting the right insulation

Every building code has a recommendation for insulation in different zones. Before selecting the insulation material, you need to know how much R-value is required for you. For example, if you live in the USA, this is your zone map and the recommended R values for different areas of your home (by Home Depot.)

Map

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Figure 1. Home Depot recommendations of R-value based on Zones.

Remember: R-value is not the ultimate standard to consider when insulating because the need for insulation varies based on sun exposure, climate, location, site surroundings etc. However, it is a good place to start in the decision-making process.

Once you know the R-value required for your region, you could opt to use a little higher or a little lower R-value insulation based on your conditions. E.g. If you are not insulating the exterior of the container, then it would be smart to use a higher R-value than recommended, as these recommended values are not meant for metal walls that tend to heat or cool more than wood.

This first step will guide you to select the right insulation material.

Type of insulation?

Once you decide the R-value you need, you must compare all the available materials based on their cost, thickness, R-value, vapour retardancy, water resistance, fire resistance, and installation method.

This article only mentions types that you should consider for a shipping container home for relevance and ease. 

Forms of insulation available in the market today

  • Boards (DIY Friendly)
  • Batts (DIY Friendly)
  • Rolled batts (DIY Friendly)
  • Spray foam (Professionals Needed)

These are listed in the order of ease of installation. If you are a DIYer, boards are the easiest and quickest way to insulate your shipping container. However, you will need to hire a professional for spray foam, as it is a messy, complicated, and experience-based process.

Materials for insulation

Boards:

  • Extruded Polystyrene foam board

This insulation consists of loose foam beads or plastic, like Styrofoam, for enhancing insulation. Extruded Polystyrene foam board (XPS), also known as blue board or pink board, comes in many different thicknesses and edge profiles.

  • Cost: They are the most commonly used boards in residential construction. Therefore, they are available at a moderate price.
    • R-value– These give an R-value of 4.5-5/ inch. The more the thickness, the more the R-value.
    • Installation- 
    • It can be installed without a professional.
    •  Fit for both interior as well as exterior insulation (with siding).
    • No framing is required.
  • Water and Fire resistance- XPS is manufactured in both or with different plastic facings and unfaced forms. However, XPS is considered a vapour retarder, not a vapour barrier, as it has a low perm rating but not low enough. This means it may absorb water but prevent it from damaging its performance.
  • It has a high melting point of 93 and 98 C, but it will be consumed by fire and emit toxic fumes in extreme conditions.

Closed-cell foam boards– 

Closed-cell foam boards are available in two types Polyisocyanurate and Polyurethane. Although, Polyisocyanurate is more commonly used, both are closed-cell foam boards with high R-Value, vapour retardancy and fire resistance. The polyiso board is typically used with a foil facing, making it more effective towards radiant heat. These are very effective in insulating shipping container homes.

  • Cost-This is the most expensive type of board insulation available but is getting very common in residential insulation.
  • R-Value- These offer an R-value of 7-8/inch.
  • Installation- The installation of these boards is fairly easy and DIY friendly. With a bit of precision and care, these can be effectively installed to get excellent performance.
  • They are lightweight and cut easily like a Styrofoam board. 
  • They can easily be fixed using adhesive
  • It can be made foolproof by applying some windowsill spray foam on the joints and corners.
  • Water and Fire Resistance– Polyiso insulation delivers a high level of inherent fire resistance than other foam insulations. It can withstand up to 198 C temperature. At a minimum thickness of one inch, Foil-Faced Polyiso Continuous Insulation has a vapour permeance of 0.05 perms and qualifies as a Class I vapour retarder. However, an installation between the studs can pose a challenge. To complete the vapour barrier, you must seal all the exposed sides with foam or tape, where the rigid meets timber/wall; otherwise, these gaps will facilitate vapour flow.

Insofast Insulation system for shipping containers

Insofast is a company that offers 2- 3.5-inch thick CX44 panels customized to fit the shipping container corrugations. With an R-value of R-11 and level III vapour retardancy capacity, its tongue and grooved system and lightweight make it an easy to install, DIY friendly product for shipping container insulation. Moreover, you can also add more boards to the thickness of the original board in order to increase the R-value, if needed.

Boards are the easiest, quickest and most DIY friendly insulation method. It is also easy to avoid error, heat loss, voids and ensure proper installation for a completely sealed container home.

Bats and rolls– 

Such type of insulation needs framing and drywall to cover the insulation. These are also not as vapour retardant as required for a metal container; however, you can always add a polyethene vapour barrier to it.

Glass fibre, Stone wool, Mineral wool are the most commonly used products in such type of insulation.

  1. Cost– They are most commonly used in residential construction in western countries; therefore, they are reasonably priced.
  2. R-value– These give an R-value of 3.5-4 per inch; therefore, they are suitable if you live in a moderate climate only. For extreme climates, such insulation will require a thickness of a minimum of 4-6 inches per side, thus eating up a lot of limited space within your container.
  3. Installation– Can be installed without a professional. This type of insulation needs framing, and the rolls or batts then go in between the 2×4 studs. While installing, one must cover the face, as these can be a bit dusty because of minute fibres.
  4.  Water and Fire resistance– Depending on the material of batt or roll, some hold moisture well, while others get wet and soggy and reduce their performance. However, all of these are fire resistant to an extent. They can catch fire but tend to prevent the fire from spreading throughout.

Spray foam insulation: 

  • Closed-cell spray foam:

In spray foam insulation, there are two types; open cell and closed cellOpen-cell spray foam is not the right fit for a shipping container as it has a lower R-value and is not effectively vapour retardant. 

Let us discuss closed cell spray foam in detail

  1. Cost– This is the most expensive but also has the highest R-value and is worth it in the long term.
  2. R-value Closed-cell spray foam offers an R-value of R-6- 7 per inch. Such a high R-value in such little space is the perfect combination for a shipping container with a limited width of 8 ft.
  3. Installation This is not a DIY solution. It is vital to hire a professional to install this type of insulation. Even though many DIY spray foam kits are available, the process is very messy and prone to errors for an inexperienced person. Following things need to be taken care of while installing closed cell spray foam.
    1. It off-gasses, so proper safety gear and expertise is needed
    1. It needs a significant time between layers for it to expand completely before the second layer covers it. 
    1. It needs to be applied with precision as it is expensive, and unnecessary wastage should be avoided.
  4. Water and Fire resistance–   Closed-cell spray foam has excellent water retardancy and fire resistance properties.

Final Words

Insulation is the most important aspect of converting a shipping container into a home. Weak or improper insulation can evoke a number of problems, including condensation, mould, rust, high energy bills and high energy load on your AC or Heater, thus causing you a lot of trouble. It is best to invest thoroughly and mindfully in insulation to achieve a wholesome, long-lasting and comfortable shipping container home.

Hope this article helps you to make the right decision.

References

  1. https://www.buildwithrise.com/stories/4-ways-to-insulate-a-container-home
  2. https://www.falconstructures.com/blog/insulated-shipping-container
  3. https://youtu.be/RJD9Tm3jC14
  4. Discover Container – https://www.youtube.com/watch?v=O5FsjwIgoWQ
  5. Live in a container – https://www.youtube.com/watch?v=GrIkQmbMIpc
  6. Insulation board types and process – https://www.insulation-info.co.uk/insulation-boards
  7. Insofast – https://www.insofast.com/resources/insulation-panels-for-shipping-containers-master-details.html
  8. https://www.polyiso.org/page/FirePerformance
  9. https://askinglot.com/is-polyiso-insulation-a-vapor-barrier
  10. https://www.containeraddict.com/shipping-container-insulation/
  11. https://offgridworld.com/8-factors-to-keep-in-mind-when-insulating-a-shipping-container-home/
  12. https://www.homedepot.com/c/ab/insulation-r-values/9ba683603be9fa5395fab9091a9131f