The Best Way to Insulate a Crawl Space (With Dirt or Concrete Floors)

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Effective crawl space insulation is essential in maintaining your home’s structural integrity. At the same time, it helps prevent rodent infestation and can improve energy efficiency. This begs the question, what’s the best way to insulate a crawl space?

The best method is by using water-resistant foam boards. These materials are proven effective in sealing away moisture and trapping heat.

In this article, we cover the steps needed to insulate your crawl space with foam boards, as well as shed light on dirt and concrete floor insulation.

What Is the Best Way to Insulate a Crawl Space With a Dirt Floor?

Different crawl space conditions require different solutions. So, it’s best to assess which type of insulation may work best for your location first, especially if you have a dirt crawl space.

Since dirt crawl spaces are prone to increased moisture and several other issues, the best way to insulate dirt crawl spaces is by using water-resistant materials like foam board.

Issues With Dirt Floor Crawl Spaces

Without proper encapsulation and insulation, this type of crawl space may present the following issues:

• Frequent flooding
• Increased moisture and humidity
• Build-up of molds
• The attraction of pests and rodents

Altogether, these issues may lead to consequences that impact your health and home.

Most importantly, the growth of molds and increased moisture result in poor air quality. Not to mention that it compromises the structural integrity of your home.

Investing in good insulators for your crawl space is crucial, as inefficient insulation results in more expensive repair costs in the long run.

Consequently, there are important practices that you should follow before you install insulation in your crawl space.

Best Practices When Insulating a Crawl Space With Dirt Floor

Foam boards are an excellent choice as they’re light and effective in sealing away moisture and controlling heat. In the same manner, it’s easy to install, unlike other insulating materials.

Before installing your foam board insulators, it’s important to address pre-existing issues, such as water or air leaks and the lack of a barrier that inhibits moisture from the ground.

First of all, ensure you have cleaned your crawl space properly and addressed all water leakage problems. Then, make sure that you properly seal vents and openings that may permit the entry of air.

Lastly, layering a plastic vapor barrier to your crawl space’s dirt floor helps limit humidity and prevent moisture, so it’s a pretty good idea to consider.

What Is the Best Way to Insulate a Crawl Space With a Concrete Floor?

A concrete floor crawl space presents more advantages compared to dirt crawl spaces. In fact, crawl spaces with a concrete floor don’t harbor molds or attract pests and rodents as much as dirt crawl spaces do.

In line with this, there are three ways to insulate a crawl space with a concrete floor:

The first option is to line the walls with foam board. The second is to install fiberglass between the subfloor joists. And the third is to spray closed-cell spray foam on your foundation wall.

While these three choices are effective, lining your foundation wall with foam boards is the best way to insulate your concrete crawl space.

Let me tell you why.

Why Is Foam Board the Best Choice?

Compared to the other two options, foam boards present more advantages.

This is because foam boards are promising insulators that prevent air and moisture effectively. Aside from that, they’re less prone to moisture damage, unlike fiberglass. To add, foam boards are lightweight, easy to install, and fairly priced.

That being said, the other options present various advantages in energy efficiency and thermal regulation. However, we must consider the following factors:

1 – Fiberglass Absorbs Moisture Easily and Attracts Rodents

Fiberglass insulation is cheaper than foam boards and is also efficient in keeping your floors warm. However, the major drawback is that fiberglass easily absorbs moisture, which may result in mold and mildew problems.

At the same time, it can be a nesting place for rats and rodents as it’s soft and fluffy.

2 – Foam Spray Is Costly and Dangerous

Closed-cell spray foam is an excellent thermal and air barrier. It’s useful in sealing tiny openings and nooks to prevent the entry of outside air. To add, spray foam doesn’t attract pests and is not easily affected by moisture.

Nevertheless, spray foam is costly and a concerning health hazard due to the harmful chemicals it contains. Closed-cell foam spray is best used by experts only.

How to Insulate a Crawl Space With Foam Board

To insulate your crawl space with foam boards, here are the things you should do:

1 – Clean Your Crawl Space

We tend to use our crawl space as storage for some seasonal items or garden tools. That’s why it’s best to clear any obstructions before we start working on our insulator later.

Moreover, there could be stagnant water or rodent droppings that you should get rid of, too. So, don’t forget to wear protective clothing when doing so.

2 – Inspect for Water Leaks

Your insulation will be useless if you don’t address your flooding problem. Hence, it’s important to identify and eliminate water sources that leak into your crawl space first. In some cases, you may need to improve your drainage system to prevent water entry.

Meanwhile, water leaks may come from poor plumbing, condensation, or groundwater requiring professional equipment. When this happens, seek the help of an expert.

3 – Cover Air Leaks

If your crawl space has vents, they should be sealed to prevent the entry of air and moisture. Any other holes or openings that allow air entry should be sealed with silicone caulk or other sealants.

4 – Install Foam Board on Walls

Installing the foam board on the walls instead of the floor joists is better. This method allows for optimized insulation and is more efficient in preventing air from passing through.

To do so, follow these simple and easy steps:

1. Measure the area of your crawl space
2. With a saw, cut foam boards according to size
3. Apply latex adhesive to the wall evenly
4. Attach foam board cuts to the wall
5. Use tape to seal joints between the boards

After installing your foam board, you may cover your floor with a vapor barrier.

Tips When Choosing the Best Rigid Foam Board

Now that you’re probably considering foam boards as your insulation partner, the best one you’ll ever find is the rigid type.

Here are some tips that you may consider:

1. Choose a termite-resistant rigid foam insulation
2. Select ones with a higher R-value
3. Use foam with reflective foil as they have increased heat insulation capacity

Final Thoughts

The best way to insulate crawl spaces, whether dirt or a concrete floor type, is by using foam boards as insulation material.

Rigid foam boards with high R-value or reflective foil are preferred because they allow more effective insulation.

On the other hand, fiberglass and spray foam is pretty considerable. However, these materials either break down easily or are a health hazard that may require expert handling.

To sum it up, foam board is the clear winner as the best crawl space insulating material.

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