The Best Types of Shipping Container Insulation

Insulation serves as the barrier between your comfortable, climate-controlled space and the harsh weather outside. When considering how to insulate a shipping container, you will find several choices, each with its own advantages and disadvantages.

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It's likely that you require insulation for your shipping container home, but which type is the most effective? The answer is dependent on your unique situation and objectives.

In this Article

In this article, we will address all your inquiries regarding shipping container insulation. As storage container homes gain popularity, understanding how to convert them into livable spaces becomes essential.

We will first analyze the critical considerations when selecting insulation, followed by an overview of the types of insulation available, and finally, we will discuss alternative insulation options.

You may have heard that polyurethane spray foam is the only insulation type worth considering for shipping containers. However, as you will discover below, this is not always true.

This article aims to provide you with a thorough understanding of insulation and guidance on how to select the type that best meets your needs. Factors to consider include the container's dimensions, geographic location, climate, and insulation-specific attributes such as cost and quality.

As we await building codes to align with shipping container construction, we can implement best practices now. This guidance is based on practical considerations and scientific principles.

Let us begin by discussing the essential aspects of controlling temperatures and examining various home insulation types.

Understanding Insulation

If you had a porch or patio exposed to summer heat, would you consider air-conditioning it? Surely not without enclosing it first!

The purpose is to keep the conditioned air (air that is either cooled or heated) separate from the outdoor air. Otherwise, you're essentially cooling the outside environment (something you've probably been advised against when leaving a door open!).

If the walls around your porch were made of newspaper or plastic wrap, they would not effectively manage the temperature despite containing the air. Why is that?

A flimsy wall can't prevent heat from migrating from the warm side to the cool side very effectively. Although the air can't flow through the wall, heat energy can still pass through its material. Thus, while the air is contained, your energy efficiency would be subpar. We recommend reviewing our article on heat transfer in container homes if you're unclear on any concepts so far!

In essence, insulation is specifically designed to inhibit heat energy from traversing through the walls (and ceiling and floor) of your shipping container home. It typically achieves this by trapping air or gases within intricate networks of tiny cells or passages.

Compared to solids and liquids, gases are poor conductors of thermal energy, making them excellent insulators. By trapping the gases in myriad tiny cells, you minimize convection within the gas and further enhance the material's insulating effectiveness.

When discussing thermal insulation, we mainly refer to conductive (and to a lesser extent, convective) heat transfer. The resistance to heat flow is quantified using an **R-value**, which is the standard for rating insulation (the higher, the better). Radiation does affect heat transfer, as described below.

Important note for metric users: The R-values mentioned in this article, across our site, and in most American publications utilize English or inch-pound units. To convert to SI R-values, multiply by 0. . Refer to this Wikipedia article for more details on unit conversions.

Need for Insulating Container Homes

By insulating a shipping container, you're effectively creating a barrierbetween the processed indoor air and the external environment. This is akin to what one would do in nearly all climate-controlled enclosed structures. As mentioned earlier, insulating materials help prevent heat from the warmer side from migrating to the cooler side, which enhances your container home’s energy efficiency by reducing the energy required for internal temperature regulation.

Unlike traditional residential structures, shipping container homes face the additional challenge of being entirely composed of steel. Given that steel is an excellent conductor of thermal energy, it proves inadequate at maintaining a different temperature inside compared to the outside environment. As such, insulation is often more indispensable for shipping container homes than for other construction types.

Moreover, a steel container can absorb significant radiant energy from the sun, ultimately heating up more than the ambient air. Unmodified shipping containers excel at keeping outside air from entering, yet they perform poorly at hindering heat transfer through their walls.

However, the poor performance at preventing heat transfer does not inherently indicate that insulation is always necessary. Climate also influences this decision.

Climate's Influence on Insulation Choices

If you're fortunate enough to live in an area where the climate allows for comfortable living without additional heating or cooling, you might not require insulation for your shipping container. Regions such as southern California and parts of the Mediterranean symbolize what many perceive as ideal climates.

Even so, residents in these regions may still find it necessary to use heating and air conditioning and should thus think critically about insulation. Whether you require climate control for your container home depends on your personal standards of comfort. Utilizing fans in warmer regions or dressing warmly in colder climates may allow you to tolerate seasonal variations without added insulation.

If you don’t inhabit such favorable climates, we highly recommend insulating your storage containers, although it isn’t mandatory. You should weigh the one-time cost of insulation against the ongoing expenses of heating and cooling your space. Additionally, you may find necessitating a larger air conditioning unit or heater without insulation. Over time, savings from skipping insulation may vanish as energy bills rise while attempting to maintain comfortable temperatures.

In summary, unless you live in a supremely favorable climate, insulation is likely necessary for your cargo container. Choosing not to insulate raises the risk of future regret due to increased heating and cooling costs. The advantages of an insulated shipping container are generally realized more frequently.

A word of caution: failing to insulate your container can complicate temperature regulation and may also expose it to condensation risks, leading to myriad issues like corrosion and mold. Our article on condensation is an essential read for all prospective shipping container homeowners.

Optimal Location for Your Container Insulation

Masonry and similar structures typically incorporate multiple material layers within their walls. The visible interior differs from the exterior, with various materials layered in between that offer structure, fire resistance, weatherproofing, thermal insulation, and vapor barriers.

In shipping container homes, the container itself is one material layer. You must decide on the placement of the container skin within the overall wall system.

The most common practice is to position insulation within the container’s interior walls. Typically, stud walls are incorporated in most designs to house plumbing and electrical systems and to support drywall or other interior surfaces. Adding insulation between the studs makes sense, allowing the exterior of the container to remain unaltered.

However, some individuals may prefer exterior insulation. In that case, you would place insulation outside the container and then cover it with weatherproof sheathing. This arrangement offers increased interior space while allowing a more curated exterior presentation for those who want to obscure the shipping containers themselves.

Key Factors for Choosing Shipping Container Insulation

Selecting the best insulation for your home involves more complexity than one might initially assume. Each insulation type comes with its own set of pros and cons, which may or may not be relevant to your specific container conditions.

We will seek to provide a broad discussion of these criteria as we evaluate various insulation options. Bear in mind that variations can occur based on region and manufacturer, so conducting your own research is crucial.

The main factors to account for while assessing your insulation options include:

• Overall Performance: Performance characteristics depend on material type, trapped gases, and whether the structure is open or closed cell.
• R-value: Reflects how effectively the material impedes heat energy transmission over a specified thickness.
• Air Leakage: Measures how well the insulation obstructs air movement through it (this is a separate but related issue to heat transfer blockage).
• Vapor Permeability: Indicates how well the insulation hinders vapor migration through and retention within it.
• Cost: Include both material costs and labor/equipment expenses based on whether you're engaging in DIY or hiring a contractor. If doing it yourself, remember to consider installation ease and required tools.
• Eco-friendliness: Many individuals are drawn to shipping container homes for the opportunity to build and reside sustainably and responsibly. The ecological implications of materials differ widely in terms of their manufacturing and installation impacts.

Categories of Shipping Container Insulation

We will discuss five overarching insulation categories here, categorized based on their physical form and installation method. Similar to how peanut butter and peanuts could fit into differing food categories, some insulating materials may straddle two or more of the categories below, particularly those available in various application forms (like polyurethane foam and cellulose).

It is vital to understand the differences among materials, as they will influence the selection of the most suitable insulation type. Let’s delve into the diverse options!

Non-traditional Insulation

This insulation category includes unconventional materials, often selected for their eco-friendliness and typically regarded as budget-friendly. However, their low R-value per inch makes them less ideal for most users unless eco-friendliness is your primary concern and you’re willing to compromise on interior space.

Despite being economical options, their practicality may be limited. They are better suited for moderate climates where temperature fluctuations are less significant.

• Straw Bale: Similar to straw used for animal feed, these are stacked like blocks. Due to their size, straw bales are only viable for external insulation on the container.
• Hempcrete: A building material comparable to concrete but with lower strength, composed of hemp.

Blanket Insulation

Available in pre-cut batts designed for standard wall heights and rolls that require cutting during installation, blanket insulation appears fluffy, compressible, and non-self-supporting, much like a household blanket except denser and made of different materials. In most instances, blanket insulation employs long fibers compressed into tight spaces, thereby forming an open cellular structure.

Typically installed between studs, blanket insulation relies on these structural elements for support since it would otherwise collapse. It is among the most affordable insulation options and typically requires nothing more than a stapler for installation.

Common varieties of blanket insulation include:

• Fiberglass Insulation: Composed of superheated sand or recycled glass spun into fine fibers. This is the most prevalent low-cost insulation type in Western nations.
• Slag Wool, Mineral Wool, and Rock Wool Insulation: Created similarly to fiberglass, yet made from minerals/ceramics or "slag," a byproduct of metal processing.
• Sheep Wool Insulation: Insulation crafted from the sheared wool of sheep.
• Cotton or Denim Insulation: Constructed from cotton, typically featuring a bluish hue due to the use of recycled denim or jeans. This is pricier but comprises a high percentage of recycled materials.

Although blanket insulation allows for moisture vapor flow, traditional construction usually mitigates this with a vapor retarder. However, as our condensation article elucidates, vapor retarders typically work poorly for container homes since the metal skin serves as a vapor barrier. By adding another layer, you risk trapping water vapor within wall cavities.

It's also worth noting that many fibers, notably fiberglass, can cause irritation to the eyes, skin, and respiratory system. Ensure that personal protective equipment (PPE), such as masks, gloves, and safety goggles, is worn while handling these materials. Consult the MSDS (Material Safety Data Sheet) or product packaging for proper handling instructions.

Loose-Fill Insulation

This insulation type relies on small granules of insulating media filled into a wall cavity. These need complete wall enclosure before application, or else you’ll end up with a pile on your floor.

• Cellulose Insulation: Fabricated from shredded recycled paper products, blown in via machine.
• Loose-Fill Fiberglass Insulation: Similar to fiberglass batts, however, less dense and not tightly packed, allowing it to be blown into spaces.
• Vermiculite and Perlite Insulation: Minerals expanded by heat, forming natural foam-like pellets suitable for wall cavities.

Due to their vapor permeability, loose-fill insulation materials aren't typically advisable for container applications.

Expanded Foam Insulation

Expanded foam is produced off-site into large foam boards and panels tailored to standard wall heights. Unlike blanket insulation, these panels can support their weight without assistance. On-site adjustments are made for doors and windows through cutting. Similar to spray foam, the gases within closed-cell expanded foam may escape over time, leading to diminished R-value.

Expanded foam is user-friendly for DIY projects, either affixed to studs or directly glued to the container. Installation is generally quick, though making cuts can be time-consuming. Some varieties are molded to fit the contours of a shipping container's walls; otherwise, there may be gaps in the corrugated areas.

In most instances, expanded foam insulation boasts the highest R-value per inch compared to all other types discussed.

• Open Cell Polyurethane Foam Insulation (oc PU Foam): Open-cell foam consists of less dense materials filled with air, resulting in a spongier texture and lower R-value.
• Closed Cell Polyurethane Foam Insulation (cc PU Foam): Gases with superior thermal conductivity fill the tiny cells, enhancing the foam's R-value.
• Extruded Polystyrene Foam Insulation (EPS): Consists of small fused plastic beads forming a closed-cell foam material. It appears as the white foam commonly used in items like coffee cups, and is what the insulation kits from companies like InSoFast are made of.
• Expanded Polystyrene Foam Insulation (XPS): Created from molten material pressed into sheets, forming closed-cell foam. Its name is similar to EPS, yet they are considerably different.
• Polyisocyanurate (Polyiso): Comparable in function to polyurethane foam, but with added rigidity.

Spray Insulation

Spray insulation can be crafted from various materials, all of which are applied by spraying or pumping out a liquid mixture that solidifies into a solid mass. Due to its application method and the self-adhering nature of spray insulation, it provides comprehensive coverage, sealing any gaps and cracks.

Spray foam insulation expands upon application and then hardens, further enhancing its sealing capability. However, it does require trimming, as the expanding foam may protrude beyond the stud surfaces.

• Open-Cell Spray Polyurethane Foam (ocSPF): This variant has the least favorable properties, as it features a lower R-value due to the allowance of air flow between cells.
• Closed-Cell Spray Polyurethane Foam (ccSPF): This variant is the preferred choice for shipping container insulation, as it usually boasts one of the highest R-values per inch while forming an effective vapor retarder. Do note that concerns surrounding off-gassing exist post-application; check with your manufacturer regarding cure times before occupancy. The gases in closed-cell types may sometimes leak over years, leading to reduced R-values.

A related but distinct option involves using non-expanding sprayed-in insulation. Unlike spray foam types, it does not chemically expand upon application but fills the cavity completely.

• Damp-Spray Cellulose Insulation: Formulated from shredded recycled paper products, this insulation uses a special rig to apply, adding water or adhesive during application (damp-spraying) that binds the cellulose while allowing for filling open wall cavities.
• Cementitious Foam Insulation: A lightweight blend of water, air, and natural minerals that resembles concrete upon curing, and looks similar to shaving cream when first applied. Though the solidified product can become crumbly if mishandled, cementitious foam remains eco-friendly, non-toxic, and non-flammable, though its R-value is lower than that of spray foam insulations.

Clearly, numerous options are at your disposal. Identifying the best insulation type requires an understanding of your individual decision factors such as budget, climate, design preferences, and personal tolerance to temperature extremes.

If uncertainty arises, examining what insulation methods are prevalent in your geographic area can simplify choices. Oftentimes, it is more cost-effective and easier to utilize materials already in common use within your region. Consulting with local construction contractors regarding site-specific recommendations may also yield valuable insights.

Refrigerated Shipping Containers

This discussion primarily pertains to adding insulation to standard shipping containers. Alternatively, you may consider purchasing insulated shipping containers previously utilized for transporting perishable goods. While there are advantages and drawbacks to this option, it can be suitable if you locate such containers at a reasonable price.

Other Thermal Energy Control Techniques That Aren't Quite Insulation

Green Roof

A green or living roof is an ecological rooftop garden composed of various grasses and plants. While soil and vegetation do not function as exceptional insulators, they can block solar energy in warm climates. Thus, a green roof serves as a complementary add-on rather than a replacement for traditional insulation.

Another appealing aspect of green roofs is their visual appeal! From above, your container home will blend seamlessly into the surrounding landscape. Although they may not be primary insulation solutions, they are still environmentally friendly and confer some degree of protection.

Reflective/Radiant Barriers

While the aforementioned insulation types primarily slow heat transfer through conduction (and somewhat convection), one must also consider radiative heat transfer. As discussed in our article on heat transfer in shipping container homes, this is a crucial, albeit frequently misunderstood aspect of heat transfer in these structures.

If you're not interested in draping your container with a mylar space blanket commonly seen among hikers, acquiring a radiant barrier will likely involve a specialized coating. Be sure to differentiate between typical paint and coatings expressly designed to reflect and emit radiant energy.

These coatings are formulated to reflect infrared light related to thermal energy and operate very differently from regular paint. More comprehensive information is presented in our article on cool roof coatings.

Passive Heating and Cooling Design

You may also design your home to minimize energy necessary for heating and cooling. Various techniques strive to accomplish this, which are beyond the scope of this article. Examples include Trombe Walls, Solar Chimneys, and others. Their effectiveness can vary greatly depending on local climate conditions.

While these passive strategies can be effective in temperate zones, they may not suffice independently. For instance, the most you can hope to feel comfortable in a passive design is akin to standing outdoors in shaded areas with a breeze. If that's not cool enough for you, the passive design may not meet your needs.

Decision-Making Process

As highlighted throughout this article, the plethora of options available for shipping container home insulation can be overwhelming. However, it’s essential to remember that insulation is merely one facet of a more extensive plan and design.

When contemplating container home insulation, it should be viewed within the broader context of your architectural vision and practical needs—consider it from day one, as it informs numerous subsequent decisions. It also has to fit into your overall budget and account for various factors such as climate suitability, installation complexity, build size, personal preferences, and more.

We aim for you to thoroughly enjoy your shipping container home. As the saying goes, happiness is reality minus expectations.

By grasping the nuances of financial resource allocation and the underlying principles of physics, plus effectively managing your comfort expectations, you'll create a project you truly love! Initiate the planning process early to hone a clear vision for your shipping container construction aspirations.

Take the necessary time to strategize the ideal shipping container home for yourself, and utilize our additional resources and eBooks to address any questions or uncertainties you face along your journey.

Conclusion

You possess a variety of insulation options, and your selection will be guided by factors like climate conditions, design specifications, and budget constraints. Each option has its merits and drawbacks, but you’re now better equipped to weigh these considerations.

Moreover, it’s worth noting that you need not restrict yourself to just one insulation type. For instance, you might utilize closed-cell polyurethane spray foam for the container walls and roof, while employing rock wool blankets underneath the container to mitigate costs.

Combining different insulation types within the same area is also possible. For example, you could opt for rock wool beneath the container, then lay down a layer of closed-cell polyurethane foam over it to establish an airtight seal. Regardless of your choices, ensure you remain aware of condensation risks if you reside in a climate where it poses a concern.

For additional related information, refer to our articles on methods for keeping your container cool and warm.

We invite you to share your thoughts below on the various insulation options accessible to builders of shipping container homes.