The crawl space in your home is one area that can be easily forgotten. Out of sight and out of mind, it’s easy to see why. But, your crawl space is an integral part of your home and should be given the attention it needs.

One of the most important things you can do for your crawl space is to ensure it is adequately insulated. Insulation helps regulate the temperature in your home and keeps moisture out.

But how do you choose the suitable insulation material for your crawl space? What are the signs your crawl space insulation needs to be replaced? In this guide, we go over the steps of replacing your crawl space insulation.

Best Materials For Insulating Crawl Space

First off, you need to choose the right insulation material. There are two main types of insulation: fiberglass and foam board.

Fiberglass is the most common type of insulation. It’s made from natural materials and is easy to install. Fiberglass is also a good choice for damp or humid environments because it is resistant to mold and mildew.

However, there are instances when fiberglass is not your best option for insulating a crawl space.

Foam board, on the other hand, is made from synthetic materials. It’s more expensive than fiberglass but is also more effective. For example, foam board does a better job of sealing off your crawl space and preventing moisture from seeping in.

When choosing an insulation material, you must also decide what R-value you need. The R-value is a measure of an insulation’s ability to resist heat flow. The higher the R-value, the better the insulation is at resisting heat flow.

If you want to opt for an environment-friendly material, you might want to try cellulose. However, it doesn’t do well in moisture-prone areas. Thus, you’ll have to replace it every five years.

Another option is structural insulated panels. They’re made of two skins of oriented strand boards with a layer of rigid foam in between. The most significant advantage of using these panels is that they create an airtight seal, which is essential in a crawl space.

How to Tell If Crawl Space Insulation Needs To Be Replaced?

There are some tell-tale signs that your crawl space insulation needs to be replaced. Here are some of them.

Higher Energy Bills

The primary indicator of inefficient insulation is an increase in energy bills. If you notice your energy bills are higher than usual, it’s time to check your crawl space insulation. 

Lack of Insulation

If you can see the ground in your crawl space, it means there is a lack of insulation. Not only is this a sign your insulation needs to be replaced, but it’s also a significant fire hazard.

If you have a dirt floor crawl space, there should be a minimum of six inches of insulation. If your crawl space has a concrete floor, the minimum insulation should be 12 inches.

Animal Infestation

Traces of squirrels, mice, or rats is a nightmare for any homeowner. You certainly don’t want bats taking up residence in your home.

If you notice any animal droppings in your crawl space, there is a hole somewhere that needs to be filled. Animals can cause extensive damage to your insulation and should be dealt with immediately.

Visible Mold or Mildew

Mold and mildew are a sign of moisture, which means your insulation is not doing its job. Not only is this unsightly, but it can also cause health problems.

If you see mold or mildew, it’s time to replace your insulation. Be sure to fix the moisture problem to prevent the mold from returning.

Sagging Insulation

Over time, insulation can start to sag. It is usually due to too much weight on the insulation or improper installation. Sagging insulation is less effective and needs to be replaced.

How to Replace Crawl Space Insulation?

How you’ll start crawl space insulation replacement will depend on why you’re replacing the insulation. For instance, if standing water is in the crawl space, you must drain it first.

Call a professional for this. They’ll either install a drain or dig a trench to divert the water. If you have a mold problem, you must remove the old insulation and clean the area before installing new insulation.

It’s also essential to make sure the crawl space is properly ventilated before you start insulating. If not, the new insulation will get damp, inviting mildew. 

Once you’ve prepared the crawl space, you can begin insulation replacement. The insulation you use will depend on the climate and your budget. Some types of insulation, such as rolled fiberglass, can be installed by homeowners. Others, such as spray foam, are best left to the professionals.

Here are the materials you’ll need to replace crawl space insulation:

If you’re taking the DIY route, here are the steps to follow:

Step 1: Measure the Space

Start by measuring the area you need to insulate. It will help you determine how much insulation you need to buy.

Step 2: Cut the Insulation

Cut the insulation to size using a sharp knife. Be careful not to damage any wires or pipes in the crawl space.

If there are any vents leading into the crawl space, cover them with a piece of plywood or cardboard. It will prevent the insulation from blowing into the vents.

Step 3: Remove the Old Insulation

Remove the old insulation from the crawl space. You can donate it to a local thrift store if it’s in good condition. Otherwise, dispose of it properly.

Step 4: Install the New Insulation

Install the new insulation by stapling it to the walls or floor of the crawl space. Make sure the insulation is tight against the wall to prevent drafts.

If you’re using rolled fiberglass, cut it to size using a utility knife. Then, fit it snugly between the floor joists and staple it in place.

The vapor barrier should face up to prevent moisture from seeping into the insulation. Install it, so the seams overlap by at least 6 inches (15 cm).

You can also install wire supports between the ceiling joists to prevent the insulation from sagging. Position the supports about 2 feet (0.6 m) apart.

Step 5: Seal the Crawl Space

Seal the crawl space by caulking around the perimeter. It will prevent moisture and pests from entering the crawl space.

After you’ve replaced the insulation in the crawl space, it’s imperative to maintain proper ventilation to help keep the area dry and avoid condensation and mold growth.

How to Stay Safe When Replacing Crawl Space Insulation?

Working with fiberglass or cellulose can be unpleasant, and it’s easy to get hurt if you’re not careful. Here are some tips to stay safe when replacing your crawl space insulation:

  • Wear a dust mask and gloves when removing old insulation.
  • Wet the area down with a hose to reduce dust.
  • Use a shop vac to remove any remaining insulation and debris.
  • Wear long sleeves and pants to avoid getting cut by the insulation.
  • Install a vapor barrier to prevent moisture and mold growth.
  • Seal any gaps or cracks in the crawl space foundation to keep out pests.

If you’re not comfortable doing the work yourself, hire a professional to do it for you.


Justin's been in construction for over 20 years in both new build and renovation. With experience in both commercial and residential construction, he specializes in healthier and more energy-efficient homes.

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