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Though we wish the warm, sunny days of summer could last forever, the inevitable march towards fall and winter serves as a helpful reminder to consider one of the most important steps in creating a narrowboat that remains comfortable year round: insulation.  

In this article, we’ll explore the different kinds of insulation used on narrowboats and cana boats, highlighting several that may be the best insulation for narrowboat warmth and comfort.

Once properly installed, these products not only promise to keep you warmer through the winter, but they also improve energy usage on your boat, too.

Types of narrowboat insulation options

There are several different kinds of insulation on the market that have proven to work well on narrowboats.  Understanding the pros and cons of each is an important step towards selecting the best insulation for your boat.

Polyurethane Foam Sprays

One of the best options for narrowboat insulation is a spray form of polyurethane foam.  This insulation is applied using a spray and allows you to create a layer of insulation as thick or thin as you need. 

This form of insulation is incredibly versatile and can be applied anywhere you think needs a little extra insulation.  Common applications for this insulation include flooring, internal walls, ceilings, and even around doors. 

Besides its versatility, spray polyurethane foam offers sound insulation, serving to reduce noise and vibrations for a more peaceful and serene narrowboat experience. 

For sound dampening effect, try spraying polyurethane foam along walls around your boat’s engine.

For comparison’s sake, many boaters prefer spray polyurethane foam to traditional rock wool or sheet insulations. 

This spray product is easier to work with and apply than sheet insulation and tends to keep a narrowboat warmer with thinner applications.

Rock wool insulation

Rock wool is a popular and more traditional insulation option.  Rock wool is a high-density material made from non-directional fibers. 

These properties imbue rock wool with both a high degree of thermal insulation as well as make this insulation an effective option for reducing vibrations and unwanted sounds.

Though spray polyurethane foam is easier to apply in some cases, rock wool is preferred by many when insulation around wiring because you won’t need to cover and protect wiring from rock wool like you’ll need to if you opt for a spray foam option. 

Rock wool is also handy for those difficult and awkwardly shaped spaces because you can easily cut it to fit any shape necessary, making this a great option for undulating around sockets, pipes, and cables.

Rock wool is also a popular option because of its safety characteristics. 

Capable of withstanding temperatures of 2,000℉ or more, rock wool carries the highest fire rating for its non-combustibility and fire protection. 

Rock wool is also handy for preventing mold because it effectively controls vapor buildup and moisture in the walls, nooks, and crannies of a narrowboat.


Polystyrene is the most common type of insulation you’ll find on narrowboats and canal boats, though this form of insulation is not as commonly used today. 

Polystyrene works well for insulating walls, roofs, and even refrigerators and freezers because it provides excellent thermal insulation.  

One of the most unique and helpful aspects of polystyrene insulation is its water resistance. 

This insulation is so common on narrowboats because it is quite long-lasting,offering a long-term solution capable of protecting narrowboats from harsh winter elements like rain, snow, and ice.

Polystyrene is easy to install but it can’t be used everywhere on your canal boat or narrowboat.  If allowed to come into contact with PVC wiring, Polystyrene can dry up and become brittle, creating potential for shot circuits. 

To keep Polystyrene insulation at peak thermal insulation effectiveness and safe for long term use, you’ll need to apply a sealant as well as have this aspect of your boat services regularly.

Tips for installing narrowboat installation yourself

Many narrowboaters delve into DIY projects, crafting their narrowboat themselves.  There are boat outfitters qualified to install insulation, you may prefer to insulate your boat yourself and according to your own specifications.

If you’re installing your own insulation, consider the following tips:

  • If using a spray foam insulation, remember that temperature impacts the way this product expands.  For more consistent treatment throughout your boat, apply a first layer and then inspect for any areas that aren’t deep enough to ensure consistent insulation throughout.
  • If using a spray gun to apply closed cell foam, clean out the spray gun immediately after every application or installation session to prevent blockages that can render your spray gun applicator useless.
  • Allowing drafts to go untreated is like trying to fill a bucket full of holes – no matter how good your heater or how much you try to warm your narrowboat, drafts and draughts will allow heat to seep out and cold to settle in.  Find the source of your drafts and take the extra step to seal these areas off to lock in warm air and prevent cold or moisture from hampering your winter comfort.
  • Don’t forget floor insulation when improving your narrowboat’s thermal efficiency.  Many flooring products are made with a thermal layer beneath and an attractive flooring vinyl on the exeter-facing size, allowing you to insulate and upgrade your boat’s floor appearance in a single step.

Best Insulation for Narrowboat

TotalBoat 2 Lb Density Expanding Foam Kit, 2 Part Closed Cell Polyurethane Liquid Foam for Boat and Dock Flotation, Insulation, Soundproofing and Filling Voids (2 Quart Kit)

TotalBoat’s Expanding Foam Kit is a lightweight liquid form of urethane offering 2-pound density that provides excellent thermal insulation as well as soundproofing. 

This insulation is US Coast Guard approved for flotation for nonstructural applications and enhances buoyancy, too.

TotalBoat Expanding Foam Kit is easy to apply and promises quick results.  This two part foam mixture is easy to mix in a 1:1 ratio, expanding and hardening in place in five minutes or less. 

This quick application time is perfect for areas of your narrowboat that require multiple layers of insulation as there is little downtime necessary for allowing the foam to harden before applying the next layer. 

Once cured, this rigid insulation consists of 94% closed cell marine grade foam that resists water absorption and damage caused by corrosive substances on your boat such as gas, oil, or other solvents. 

Once cured, you can also coat this foam insulation with polyester, vinyl ester, or epoxy for added water resistance. 

This foam can also be shaved, carved, and cut to best fit awkward spaces.


  • Made of 94% closed cell marine grade foam for optimal thermal insulation
  • Naturally water, oil, and flame resistant
  • Easy to mix and apply with a 1:1 ratio


This foam insulation mixture requires proper temperature, timing, thorough mixing, and proper ventilation to ensure full expansion.  Ideally, this product is easiest to work with in temperatures between 75-85°F.

XCEL Extra Large Marine Roll, Closed Cell Neoprene Rubber with Adhesive, Size 60″ x 16″ x 1/2″, Easy Cut Material, Water and Weather Resistant, Made in USA

Made of closed-cell foam rubber, XCEL marine rolls are naturally non-absorbent, durable, and extremely buoyant. 

This insulation is not only water and oil resistant, it is also flame resistant, too.  Marine rolls are perfect for adding layers of thermal insulation to your boat’s interior as well as providing additional soundproofing.

These rubber sheets and rolls are incredibly versatile and can be used in multiple ways around your narrowboat. 

They can be placed on sets or under furniture to prevent sliding and add cushioning, but they are also useful for lining hulls and cabins. 

This insulation features a strong, pressure sensitive adhesive side that makes installation quick and easy.

XCEL insulation and marine products are made in America by a small, private company. 

This small operation focuses on crafting high quality products and prides itself on leveraging its small company size to create better customer relationships and provide enhanced customer service.


  • Versatility of marine rolls makes this a great tool for insulation as well as adding cushion and slide prevention
  • Naturally water, oil, andn flame resistant
  • Adhesive side makes installation quick and easy


  • Though this insulation features a strong adhesive, the company still recommends adding mechanical methods of holding the insulation in place, such as staples, nails, or other traditional methods for hanging insulation.  The adhesive side of this insulation helps to place the insulation where you want it and makes it easier to install.

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