RV Underbelly Insulation 101 - (Everything You Need To Know) (2023)

RV Underbelly Insulation 101 - (Everything You Need To Know) (1)

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Are you in the market for a new RV and confused by “RV Underbelly Insulation” listed under the non-standard features?

Maybe you have an older RV and you’re looking to add underbelly insulation to your rig, already aware of the many benefits.

Or perhaps your current underbelly insulation is getting old and in need of replacing.

No matter the reason, let’s learn about RV underbelly insulation and why it might matter to you, especially you plan on doing any winter camping!

What is RV Underbelly Insulation?

RV underbelly insulation is exactly what it sounds like: insulation made for the underside or underbelly of your rig. It is not always a standard feature, especially on older rigs, but you may find yourself wondering why it isn’t standard once you learn more!

RV underbelly insulation is often hidden beneath your RV’s protective underbelly plastic, usually, a material known as coroplast. You may not have this special protective layer if you own an older rig, but it may be worth looking into, especially if you install some insulation and need to protect it!

RV underbelly insulation may feel like a strange addition to any rig but it is there to protect your pipes, warm up your floors, and keep the inside of your rig more fully insulated! It is definitely a more in-demand feature now than it ever has been before.

And for good reason!

Does My RV Have Underbelly Insulation?

You may be wondering if your existing RV already has underbelly insulation. You may not be able to tell right away, especially if your insulation is properly covered by a thin sheet of coroplast.

However, should you have coroplast beneath your RV, it should be a fairly easy removal process. They are often held to your trailer’s frame by some simple screws or other attachments. Chances are, if you have a coroplast cover for your undercarriage, you have insulation inside of it.

Many suggest not altering your coroplast covering in any way unless it is already damaged. Moving the plastic sheeting may result in damage to it or the frame. An RV dealer or authorized repair shop may be your best bet should you need your underbelly insulation looked at.

However, if you’re planning to replace your coroplast or are a more skilled handyperson than the average RV owner, feel free to remove your coroplast cover to check on the status of your insulation! Many RV owners who have done their own underbelly repair report satisfaction in doing it themselves, reporting that they learned a lot more about how their trailer works.

The underbelly hides a lot of important things, and you may find fixing it yourself to be an informative task. Propane lines, water lines, black and gray water tanks, and other necessary RV components lie beneath your frame, and it’s always a good idea to familiarize yourself with things of that nature!

What Are the Benefits of Underbelly Insulation?

Underbelly insulation is a wonderful feature that may or may not come standard if you are shopping for a new RV. I wish my 1976 travel trailer had it, but it is a newer development in the RV world. I am attempting to install it myself, as the benefits far outweigh the cons!

Added Insulation

As the name suggests, underbelly insulation adds a wonderful layer of insulation to the floor of your rig. As a full timer, I find I lose a lot of heat in the winter through my floor. If I had underbelly insulation, I have no doubt that my heater wouldn’t have to work so hard!

The same goes for your air conditioner too. Cold air sinks while hot air rises, which means you no doubt are losing that wonderful cold air through your bare floors! If you had underbelly insulation, it would assist in the efficiency of your air conditioning unit.

Underbelly insulation is most important in winter, given how harsh winter temperatures can get. However, even if you only camp in the warmer months, this extra layer will greatly improve the use of your air conditioner. Underbelly insulation is often the number one addition to make when considering a 4 season RV versus a 3 or less season rig!

Protection for Pipes and Tanks

Underbelly insulation is a great invention for your RV’s water lines, pipes, and tanks. Some underbellies are heated on newer RVs to protect your water lines from freezing in the winter. This can be a devastating repair for RV owners, should a pipe freeze and burst.

Underbelly insulation, whether heated or not, can protect your intricate water system, as well as keep both your gray and black water tanks from freezing too. You’d be amazed how much a few sheets of insulation and coroplast can help when it comes to cold weather camping! You’ll likely never have to worry about your pipes freezing again.

Protection for Your RV’s Frame and Subfloor

Since my RV is a tad on the older side, I have had to deal with corrosion and holes in my trailer’s frame. I do not have a protective coroplast sheet underneath my rig, and the holes in my trailer’s frame came as an unwelcome surprise. I have now replaced all of my rig’s flooring due to water splashing up through the holes and damaging my subfloor!

(Video) RV trailer - Installing Underbelly Protection (Part 1)

If I had had underbelly insulation and a coroplast cover, I would not have had this issue. My frame, no matter how old, would have been protected from water damage and other potentially damaging items found while traveling. Rocks, debris, branches, and other things found while driving will be deflected by the coroplast, keeping your frame and subfloor safe!

Rodent and Other Pest Deterrent

Having an intact coroplast cover as well as underbelly insulation can be a natural pest deterrent. The watertight seal often associated with underbelly protection also defends your rig from mice, chipmunks, spiders, and any other pests that may want to make your RV their new home.

Having underbelly insulation and protection may be increasingly valuable to those of you that store your RV at any point. Pests often seek RVs as shelter in the colder months, and it is easy for mice and the like to squeeze their way through any hole in your frame. If you have a completely intact coroplast cover and insulation above that, the chance of a pest getting through is a lot slimmer.

Because of the persistence of pests, you may want to inspect your underbelly often, especially if you plan on storing your rig come winter. Any crack or hole in your underbelly is a doorway for pests, and you may not realize you have an issue until it’s too late!

What Are the Cons of Underbelly Insulation?

While underbelly insulation is not often a standard feature, there are only a few reasons not to consider it. However, these cons should be noted, especially if you have existing underbelly insulation and plan on replacing it.

Covers Shoddy Workmanship

Some RVers who have had to replace their underbellies find that their rig has been put together poorly, sometimes even finding damaged pipes or other manufacturer errors. If you are concerned about the build of your RV, especially if you begin experiencing operation errors, your underbelly may hold the answers. However, these answers are usually covered up!

Some ambitious do it yourself-ers tend to remove the underbelly cover on their rigs, just for their own peace of mind and maintenance access. Some RVs are built better than others, and you may find that having so many key parts of your rig covered up is not a perk.

Coroplast is NOT Pest Proof!

You may think that having a coroplast cover over your RV’s underbelly will completely protect it from pests, especially rodents. However, coroplast is a very thin, flexible plastic material and is no match for rodent’s teeth. Should your coroplast be damaged in any way, or should you store your RV with food inside (this is not a good idea), a rodent will find its way in, no matter what.

This is something to keep in mind, especially when it comes to the maintenance of your underbelly. While a coroplast cover may be another layer and deterrent for many pests, it is not a fail safe!

Weight of Underbelly Insulation

While you should never purchase an RV that comes close to your tow vehicle’s maximum capacity, the weight of your underbelly’s insulation may be a factor. While coroplast and insulation sheets don’t tend to weigh much, some underbelly insulation can add significant weight to your rig.

Most of the time, RV manufacturers don’t make underbelly insulation very heavy. However, if it is a fix you plan to do yourself, or if a prior RV owner has done their own underbelly protection, make sure you know the materials being used. Sometimes heavy metal or insulation can be used, adding a lot of unnecessary weight to the bottom of your rig.

While this is usually a rare occurrence, it is worth considering, especially if your tow vehicle is made for lightweight rigs in the first place!

Types of RV Underbelly Insulation

Whether you have underbelly insulation already and are hoping to replace your current stuff or perhaps install from scratch, it’s important to know what types of insulation are out there.

The most common RV underbelly insulation products are listed below.

Rigid Foam Board

This insulation is available at hardware stores in various materials. These boards are the most common type of underbelly insulation due to their affordable price point, ease of installation, and moisture resistance. They are also fire-resistant, though can give off harmful fumes should they ever catch fire.


This type of insulation is also readily available at hardware stores and is fire resistant. Rolls of fiberglass insulation are usually affordable but can be dangerous to handle due to the nature of fiberglass. You may also find it a difficult material to work with as it tears easily.

Spray Foam

This is the most flexible insulation option, capable of spraying on most anywhere. This can be valuable for a tricky underbelly, as you won’t have to measure and cut your insulation. However, spray foam can be very messy as well as costly.

No matter the option you choose, all of these materials are viable and useful for insulating the underbelly of your RV! You may wish for a professional to help you install your insulation, and they may recommend some materials over others. However, if you’re looking to install your underbelly insulation yourself, read on!

How to Insulate Your RV Underbelly Yourself

The time has come: you’ve decided to replace or install insulation along the underbelly of your RV. And you’ve decided to do it yourself! There’s nothing better than the feeling of a job well done, and it may save you a pretty penny if you choose to tackle this job on your own.

Here’s a step by step guide to insulating your rig’s underbelly! Take the time to gather the supplies and tools you think you’ll need, such as screwdrivers for removing parts of your RV’s underbelly, utility knife for cutting the insulation, tape measure for accurately measuring the underbelly, etc.

Also always wear protective equipment such as a headlamp, gloves, and eye goggles or glasses. You never know what might happen when repairing any part of your RV!

(Video) Winter RV Living 101: How to Insulate the Underbelly of Your RV - Part 1

1. Measure Your RV’s Underbelly

Whether you’re planning on using spray foam, fiberglass, or rigid insulation sheets, you need to accurately measure the underbelly of your RV before procuring supplies. Use a tape measure and measure every bit of your RV that you plan on covering with insulation.

Should you be installing rigid foam, make sure you measure more accurately so that you can cut the sheets to fit. It will make the process a lot smoother if you measure your pieces and cut them all before you begin installing!

2 Remove Coroplast, Existing Insulation, and Other RV Parts

Your underbelly is complicated, whether you have existing insulation or not. Removal of your existing coroplast and insulation should be a fairly easy task, but disconnecting the various pipes and tubes beneath your RV might be more complicated. It is necessary to do however, just in case damage occurs during the installation of your new insulation.

Don’t be shy about labelling your various lines and wires with tape, and take photos of what your underbelly looks like before you begin removing the more complicated parts. This may seem time consuming, but it will make reinstalling everything a breeze. Plus, the last thing you need is to install something incorrectly!

3. Installation!

The moment you’ve been waiting for (or perhaps dreading): installing your new insulation! Hopefully you’ve cut out your rigid foam pieces, or trimmed up your rolled fiberglass insulation by now. Begin puzzling them together beneath your rig, using screws or liquid adhesive.

If you are using spray foam, it should be fairly self explanatory to install. No matter what insulation material you plan on using, always begin at one end of the RV and move to the other to ensure a tight finish.

5. Put It All Back Together

Success! Your insulation looks amazing, all of your pipes and tanks are covered and warm. Now it’s time to put everything back to operating conditions. Hopefully you labelled your bits and pieces, so installation should be no problem.

Your coroplast cover comes last, and your RV’s underbelly should be all set once this is installed! Make sure the coroplast is undamaged and completely covers all of your new beautiful insulation. Good job!

Products to Help With Insulating Your RV’s Underbelly

Unsure what products to turn to when it comes to replacing your RV’s underbelly insulation? Here are some good options to assist with your DIY investment, so that you don’t have to stress!

Best Spray Foam Insulation: Touch N Seal Black UV-Resistant Polyurethane Gun Foam Spray Sealant Kit

RV Underbelly Insulation 101 - (Everything You Need To Know) (2)

Touch N Seal Black Landscape and RV UV-Resistant Polyurethane Gun Foam Spray Sealant Kit - 10/24oz...

  • A black, UV-resistant gun foam specially formulated to blend in with landscaping, RV, automotive, HVAC and other applications.
  • Gun Foam Black Packaged in 24 oz. cans. Each Can Theoretical Yield (¼" bead) is 3,200 linear feet, Class A fire resistance
  • Black color for blends in with black piping and auto undercarriages, Formulated to resist discoloration in exterior applications

While your needs may vary depending on the length of your rig, this handy kit from Touch N Seal includes 10 24 oz cans of UV resistant spray foam as well as a couple cans of spray foam remover, should you accidentally get the product anywhere you’re not supposed to! This foam insulation is recommended for many projects, your RV underbelly among them.

While it may be a bit more expensive than other types of insulation, this spray foam is water and fire-resistant, so that you don’t have to think about it once it is installed. It is also a wonderful pest deterrent, creating a seal against rodents and spiders. There are many tutorials for this product, and it should be fairly self-explanatory to use these cans!

This product reaches a full cure in one hour should the temperatures be mild, and it is a discreet black color that resists UV fading. While it may require separate purchase of a professional spray gun, this product may be worth it for many folks. You can see the latest price and read more reviews on Amazon by clicking here.

Best Rolled Foam Insulation: SmartSHIELD -5mm 48″x50ft Reflective Foam Core Insulation


RV Underbelly Insulation 101 - (Everything You Need To Know) (3)

SmartSHIELD -5mm 48"x50ft Reflective Foam Core Insulation roll, Cold and Heat Shield, Radiant...

  • EXTREMELY EFFECTIVE - reflects 95% of radiant energy, R -value up to 15.67 with one layer.
  • ALL IN ONE PRODUCT - Insulation (R15), Radiant Barrier, Vapor Barrier, Sound Barrier.
  • EXCELLENT LOOK - Clean white look, requires no painting, No additional insulation required.
(Video) Winter RV Living 101: How to Insulate the Underbelly of Your RV - Part 2

Used in a variety of applications, this SmartSHIELD insulation bundle may be the answer to your RV underbelly insulation prayers! Using advanced technology, this insulation is vapor and sound resistant along with reflective, all in a 5 mm thick roll! This set also comes with various rolls, all different widths, so that you hopefully don’t have to cut as much!

This handy roll of insulation has a clean white finish as well as being made of fire resistant materials. It is reportedly very easy to install, and maintains very high ratings for both heat resistance (such as radiant pavement beneath your rig) and temperature retention (such as controlling the climate inside of your rig).

While it may be a pricier insulation option compared to fiberglass rolls or rigid boards, it may be a great choice for those of you looking for a fairly easy installation and moisture resistant material. You can check out more reviews from RV owners and see today’s price on Amazon by clicking here.

Best Underbelly Cover Replacement Material: VIBE INK Bundle 24″ x 36″ Corrugated Plastic

RV Underbelly Insulation 101 - (Everything You Need To Know) (4)

248 Reviews

VIBE INK Bundle of Extra Large Blank White Yard or Lawn Sign Boards 24" x 36" Corrugated Plastic...

  • ✔ Sign Size: 36 inches in length x 24 inches in height; Short Vertical Flutes. Made in the USA!
  • ✔ Great for Garage Sales, Parties, Businesses, Clinics, Real Estate, Construction, Political, Graduations & More!
  • ✔ Use: Indoor OR Outdoor use - Waterproof and Wind Resistant! Display in your lot, front yard, lawn, garden or any area with grass!

Are you surprised to learn that coroplast is essentially plastic yard sign material? Surprise no more, and consider this large bundle of coroplast signs from VIBE INK. Coming in a 24 pack, these 36”x24” signs will no doubt cover your rig’s underbelly, and hopefully leave you with some leftover should you ever need to patch it!

(Video) REPLACING Our Campers Underbelly - FINALE (Pt. 4): Insulation & Underbelly Material

While this doesn’t seem like the sturdiest material, it will protect your RV’s underbelly and it is water and wind resistant. It is easy to install, though make sure to seal up any cracks or spaces between your coroplast. Any empty space or weakness in installation will no doubt be found by pests! You can click here to see the latest price on Amazon.

Best Underbelly Repair Tape: Mobile Home RV Flex Mend Belly Bottom Repair Kit

RV Underbelly Insulation 101 - (Everything You Need To Know) (5)

Mobile Home RV Flex Mend Belly Bottom Repair Kit-Fix Holes & Rips 48" x 14' (1)

  • Underbelly Repair Kit
  • 4" x 44 Foot Adhesive Flex Mend
  • 4" x 14 ft Non Adhesive Mobile Flex

Looking for help repairing your RV’s existing coroplast underbelly? Check out this handy kit from Flex Mend, a bundle including a non-adhesive flexible roll and an adhesive tape-like roll of their signature product.

While this is not a solution if you’re like me and have a couple holes in your metal frame, it is a solution if you just need some coroplast repair on an existing insulated underbelly. It is just like duct tape: unroll, peel, and stick! Anyone can use this product, though if you use the non-adhesive version you’ll need to purchase an additional adhesive for it. You can see the latest price on Amazon by clicking here.

Best Tape Measure: General Tools LTM1 2-in-1 Laser Tape Measure

RV Underbelly Insulation 101 - (Everything You Need To Know) (6)

General Tools LTM1 2-in-1 Laser Tape Measure, LCD Digital Display, 50’ Laser Measure, 16’ Tape...

  • VERSATILE: The Laser Tape Measure combines a 50ft laser measurer with a 16ft tape measure
  • ONE BUTTON: Simple, one button operation enables fast and easy long distance laser measurements
  • MEASURE FASTER and FURTHER: Measure up to 50-feet with the laser, and measure twice as far as a standard 25ft. tape measure

So you’re ready to replace or finally install a protective underbelly on your rig. Chances are, your average tape measure isn’t going to cut it, especially if you own a large enough rig! This tape measure from General Tools features a standard 16 foot metal tape measure as well as a digital laser measurement system.

A laser tape measure? How cool is that!? You’ll be the envy of the neighborhood, as well as a happy camper taking measurements from beneath your cramped rig. The laser side of this tape measure can range up to 50 feet, so that you can measure from one end of your rig to the other no matter how large!

Easy to operate by one person, featuring a large LED display, you’ll feel like the ultimate DIY expert! This should help save you some time when it comes to measuring, and we all know what they say: measure twice, cut once! Check out today’s price on Amazon by clicking here.

(Video) DIY RV Underbelly Repair | Coroplast Repair | rv repairs and upgrades

Understanding the value and perks of RV underbelly insulation is important, especially if your rig doesn’t have any installed yet. Whether you go to an RV dealer or do the work yourself, having an insulated underbelly is a wonderful addition to any rig. Your feet will thank you should you take the camper out this winter!


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