How Much Does It Cost to Replace Insulation Under a Mobile Home?

Problems with insulation need to be fixed immediately lest they take a toll on your energy bills.

A compromised undercarriage may allow pests to creep into the home or cause inconsistent temperatures.

The first and obvious factor to consider is the cost of the whole project.

But, How Much Does It Cost to Replace Insulation Under a Mobile Home?

We can only make estimations because a lot is at play. However, the cost will mainly depend on the size of the space or extent of the job and the type of insulation material.

The whole project can be broken into two stages:

Stage 1: Removal

The first task on the list is the removal of old or damaged insulation.

If you hire a professional for the job, expect to incur anything between $1 – $1.50 per sq. ft. exclusive of disposal cost.

Blown-in insulation is harder to remove compared to bars or batts because the former requires large vacuum machines to remove.

Note that you can’t reuse old or damaged insulation material because the R-value is more likely to have reduced.

If you didn’t know, R-value (or Resistance Value) determines how good the insulator is at the job – the larger the value the better.

Stage 2: Replacement

When it comes to replacement, expect to spend anything between $2 – $7 per sq. ft. for most blown-in insulation materials.

Considering that only certain types of insulation materials are recommended for the underbelly of the home, and the fact that the cost varies between types of materials, we’ll take a glance at each in their special section later on.

Anyway, the typical replacement cost staggers anywhere between $1400 and $6300 (exclusive of labor).

The national average is $2900 (also elusive of labor).

Not All Types Of Insulation Are Suitable For The Underbelly

The bottom part of your home is closer to the ground than any other part, meaning it’s more vulnerable to moisture encroachment.

So the material should be water-resistant or else it will absorb the moisture, rot, and turn the whole space into a mess.

Also, rats and other small animals might try to establish homes in the undercarriage.

So, not only should the material offers resistance to water but should also be uncomfortable or hard to gnaw on.

Rigid Insulation Materials Are The Best But Slightly Costly

As far as cost is concerned, you will need to make your choices carefully because the perfect materials for the underbelly happen to the costliest (correction: just a little costlier).

The best insulation materials for the job are the rigid type, like Polyisocyanurate.

Spray foams are great for the underbelly of your home and are cheap even though they don’t fall in the rigid class, so we’ll add them to the list for that reason.

Fiberglass isn’t competent enough for the task because it absorbs moisture, but we’ll explain why we added it to the list later.

1. Spray Foam Insulation

The best thing about spray foam insulation is that it lasts longer (about 3-4 times longer than fiberglass). It’s available in two types – closed cell and open cell.

Closed-cell spray foam is the only option good for your home’s crawlspace as it doesn’t soak moisture.

Installation Cost

Unlike rigid insulation options which are sold as solid boards or sheets, spray foam is sold in kits filled with a foamy material.

This makes it difficult to estimate the cost of the project based on the foam itself.

For closed-cell foam, expect to spend anything between $0.44 – $1.55 per board foot covered.

What’s a square board, you might ask? Well, since we’re dealing with a foamy material, by “square foot” we mean an area the size of a square foot slab measuring 1” thick.

See it as one square foot covered by 1” of spray foam. Got it?

If you go for expanding foam, you will spend anything between $0.50 – $2.50 a square foot.

However, this time it’s hard to make more precise estimations of the cost of installation per square foot because the thickness will vary widely (just as the name of the foam suggests).

Here’s a rough estimation though:

Size of the space in ft2 Price (estimate)
100 $45 to $150
200 $85 to $300
300 $130 to $450
400 $175 to $600
500 $220 to $750
1000 $440 to $1500

$660 to $2250
2000 $880 to $3000
2500 $1100 to $3750
3000 $1320 to $4500

These estimations are based on the assumption that the expanding foam will remain to be 1” thick.

You can multiply the price with extra inches to get more precise estimates.

2. Polyisocyanurate

Few insulation materials combine versatility and high performance as perfectly as Polyiso.

But what makes it especially suitable for underbelly installation is its ability to adhere evenly on continuous surfaces.

Unfortunately, it’s a little costlier than most insulation options partly because of the high R-value (6 – 7 per inch).

Installation Cost

The cost will depend on the size and thickness of the board.

Polyiso is normally sold in two board sizes – 4’ X 4’ and 4’ X 8’.

Thickness varies between 1” to 4”. Of course, more square feet and thickness means more money to spend, and the more boards your project requires, the higher the cost.

Let’s look at the figures:

As you would expect, the type, square feet, and thickness of polyisocyanurate influence the price.

The average price per sqr. ft. per inch is anywhere between .35 cents and .42 cents.

To know the cost per square feet per inch, divide the price tag on the board by the sq. ft. of that board.

Here’s an example:

Let’s say a 1” thick polyisocyanurate board measuring 4’ x 8’ has a price tag of $13.10.

The total sq. ft. is 32 (4’ X 8’). So the price per sq. ft. can be obtained by $13.10/32, which is .40937 or .41 cents per sqr. ft.

It is important to note that the price per sqr. ft. reduces with increasing thickness.

Also, the climate of your region can influence the amount of Polyiso needed for the project. As such, check your area’s climate map with your contractor.

3. Fiberglass

Fiberglass isn’t particularly a great insulation material to put under your home.

But since a mobile home’s floor can be divided into 3 parts, you can put it on the topmost part of the floor if necessary (fiberglass is cheaper and you’re trying to insulate on budge).

Also, you will need to ensure that your home isn’t sitting on wet ground (must be a safe distance from the undercarriage).

Installation Cost

The cost of installing a layer of fiberglass under the floor is going to depend on where your home is located. Other factors like labor and the size of the floor are worth considering as well.

On average, a square foot costs anything between $0.88 – $1.64.

For a 500 sq. ft. floor, expect to spend $300 – $600 inclusive of labor.

Since fiberglass batts can be installed with minimal DIY skills, expect to spend $25 – $50 an hour on labor, and that’s, again, if it’s very necessary.


To summarize everything, the cost of an insulation replacement project will depend on the material of your choice, the size of the space, and whether you’re hiring a contractor or taking the DIY route.

It’s hard to make a more precise estimation because of so many factors involved but it won’t exceed $2500 for a 1000 sq. ft. space.