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A Full Belly is a Happy Belly: Insulating the Underbelly of Your Mobile or Modular Home

Insulating the underbelly of your mobile or modular home can help improve its energy-efficiency. Learn how foam can help.
underbelly insulation for mobile or modular homes

If you’re here reading this blog, you are probably looking for ways to improve the efficiency of your mobile or modular home. Maybe you’ve noticed cold spots in your home. Perhaps it is always harder to keep one of the rooms in your home comfortable – it is always a little hotter or colder than the other rooms. Maybe you are hoping to have a more energy-efficient home. Whatever the case, taking a look at your home and how it is insulated is a great place to start.

Energy Inefficiency – The Facts

Here are some startling facts about energy consumption and waste in the United States. According to, 40% of the energy used in the U.S. is from homes and commercial buildings. The average American will spend about $2,000 a year paying for energy. Research shows that between 10% – 20% of that money is wasted due to drafty homes, air leaks because of lack of air seals, and outdated HVAC systems. That’s $200-$400 EVERY YEAR that is literally just going out the window!

Energy Inefficiency – The Solution

The good news is that there is a solution for this, and it starts with your mobile home’s insulation. But where should you start? The attic? The walls? Well, the National Renewable Energy Laboratory worked with the U.S. Department of Energy to test manufactured homes and their energy effectiveness. They found that heat loss was reduced by 11% when homeowners added insulation to the underbelly of their mobile or modular homes.

What is the Underbelly of a Mobile Home?

The next thing you might be thinking is, “That sounds great! I would love to stop losing heat in my mobile home…but what is the underbelly?” Well, here is the answer. The term “underbelly” describes the entire area beneath your home. However, when we talk about insulating your underbelly, we refer to the area between your floor and your belly board. (We often refer to belly boards as belly wrap, bottom wrap, bottom board, and belly barrier.)

How Should I Insulate the Underbelly?

When answering this question, you will want to consider two things:

  1. What do you hope to get from your insulation?
  2. How much are you willing to spend on your insulation?

The most common type of insulation used in homes is fiberglass. Fiberglass can give your home the needed R-values to stop heat conduction; when heat passes from one place to another by physical touch. You can put bats of fiberglass between the floor joists under your home. You can also use blow-in insulation containing tiny bits of fiberglass and cellulose. These types of insulation will do an adequate job when insulating your home, but they have many shortcomings.

One issue you will run into with fiberglass and cellulose is that they lose R-value if they come into contact with moisture. Not only that but once wet, they are excellent breeding grounds for things such as mold and mildew. If fiberglass is not installed correctly, for example, packed too tightly or squished to fit around wires and pipes, it will lose its r-value and be less effective. Eventually, this type of insulation will need replacing as it begins to sag and compress over the years.

Also, these types of insulation do not offer an air-tight seal. Without this air-tight seal, air can pass through your floor. Heat rises.

Foam Insulation for Mobile or Modular Homes

A better option for insulating the underbelly of your mobile home would be to use spray foam. Spray foam offers great R-values as well as a bunch of other significant factors. The foam acts as a vapor barrier, which blocks moisture from getting inside the walls and floors of your home. Therefore, it is not a breeding ground for mold or mildew.

Foam also fills in all of the nooks and crannies in your home to create an air seal that will keep air from freely passing through the floor of your home. Having an air seal means that you will be saving money instead of shelling it out to the energy companies. Not only will this help you stay warm in the winter, but it will help you stay cool in the summer. Lastly, foam doesn’t need replacing. At RetroFoam of the Carolinas, we offer a lifetime warranty that will last the lifetime of your home.

Now that we’ve discussed the benefits of each type of insulation, let’s talk about price. Upfront, fiberglass and blow-in insulations are less expensive than spray foam. However, spray foam will save you money in the long run as it is more energy-efficient and never needs replacing.

Contact Us

If you are interested in learning more about insulating your mobile home, we would love to help you. Please contact us today to ask any questions you might have or to schedule a consultation.

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