A well-insulated crawl space is an ideal solution for keeping your home off of the ground. The foundation prevents any water pile up — it’s especially essential if you live in a region with a humid or cold climate. The key is to have a perfect crawl space insulation for your home. 

If this space is not properly sealed, encapsulated, or ventilated — there are high chances that it will create a dark, damp, and humid environment. An unhealthy setting that’s perfect for mold and fungi growth. And, it’s a vicious circle — once the mold and mildew start growing, they will get into the vents and even between cracks in your floorboards — letting in more allergens.

Moreover, if your house was built before 1990 (before the energy-conserving building codes were standardized), chances are your crawl space insulation will be missing altogether! 

With an ill-sealed crawl space, you will end up letting the outdoor air into your living space, creating an uncontrolled situation that will affect the rest of the home’s air quality and temperature.

Good crawl space insulation can improve the indoor air quality in your home besides reducing your energy bills. It helps maintain the entire home’s energy efficiency. 

The goal of insulation is to enclose your living space in a thermal envelope. If there’s no insulation, you may easily lose heat and cool air through the floor. No wonder, maintaining a crawl space is so important. 

To understand insulating crawl spaces better, let’s explore the types of crawl spaces first.

Types of crawl spaces

There are two types of crawl spaces — ventilated crawl spaces and unventilated crawl spaces — each one requiring its own form of insulation. 

As the name suggests, the former one is ideal because it helps eliminate any moisture. Usually, fiberglass insulation is installed under the subfloor between the floor joists. You can opt for more energy-efficient options such as ridge board, spray foam, or cellulose. 

(This step is usually for areas with a moderate or dry climate. Where winter temperatures are extreme, most homeowners prefer wall insulation. In fact, it’s best to seal off the crawl space entirely in such cases.)

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The next step is to secure the insulation and cover it with a vapor barrier. This is important in order to prevent moisture and the subsequent mold formation. 

What Are The Different Types Of Insulation For Your Home? Let’s find out!

If your crawl space isn’t ventilated, you need to insulate the crawl space walls rather than the subfloor of the room above. This will eliminate the need to insulate the ducts and pipes separately. You may also install a polyurethane vapor barrier over the dirt floor. Covering it with sand will prevent any damage to it. And, this will ensure further protection. 

No matter what kind of crawl space you have, or the material you choose, insulating and sealing it is crucial. It will help improve the comfort and efficiency of your entire home. 

Although a crawl space insulation sounds simple enough and may be installed by a handy homeowner, we recommend hiring a professional for a seamless job. The contractor can finish the insulation in a fraction of the time that you would take. Not to forget that it will give you the peace of mind that a pro is handling the job. The contractors will even clean up and dispose of the old insulation — often spraying the space with bactericides and fungicides.

Symptoms that you need a new crawl space insulation

Damp, dangling insulation is a sure sign of shoddy or outdated installation. 

An improper crawl space insulation will lead to the floor above the crawl space to be cold and uncomfortable to walk on barefoot or in socks during winters. Another sign of deterioration will be the musty odors coming up from below. 

Your crawl space insulation has to be correct. Otherwise, it can easily facilitate the growth of mold and mildew in the dark, damp crawl space.

Do you want to have all your facts straight for your upcoming renovation process? Take a look at our ultimate guide on home remodel.

Using the right crawl space material

Fiberglass batt insulation has become a tad old-fashioned today. Though it’s cheaper than other types of insulation and also widely available, it has its downside. It has a tendency to absorb moisture and encourages the growth of mold. In some cases, it may sag or fall out of place. Even harboring mice in crawl spaces.

The best insulation material for crawl spaces is a rigid foam insulation board. You can install the board against the crawl space foundation walls instead of between floor joists. Unlike fiberglass, a properly sealed foam board does not absorb water, support mold, or allow air to pass through.

You could research some more and choose the material that suits your requirements.

Read more: Crawlspace encapsulation

How to insulate crawl space to improve energy efficiency

Want your crawl space insulation to be proper, and your home NOT constantly lose heat? Here are some steps you can take:

  1. Remove any source of water from your crawl space: A proper crawl space drainage system will ensure that your space is kept dry. For this, you could install a crawl space sump pump or drainage matting for the crawl space floor.
  2. Insulate your crawl space walls and the ceiling for maximum climate control: You could opt for thick insulation with a radiant barrier and an R-11 value. It will keep out all the outdoor air. As a result, your crawl space will stay warm during the winter and cool in the summer.
  3. Opt for mold-resistant, waterproof insulation: Consider using ridge board, spray foam, and cellulose instead of fiberglass.
  4. Seal all vents and openings in your crawl space: Sealing prevents the outdoor air, especially unwanted drafts, from getting into your house and helps keep the indoor air quality healthy.
  5. Seal all rim joists and sills: Use a foam sealant for best results.
  6. Install a vapor/moisture barrier to keep your basement dry: With a quality barrier, you don’t have to worry about basement flooding or controlling mold and rot. It will also seal away any unpleasant odors.

These crawl space insulation and waterproofing steps will help you save time, money, and a lot of hassles. 


If you find it uncomfortably cold to walk around your living space, despite your home furnace blowing a full blast, the culprit is sure to be your shoddy crawl space insulation. It’s letting in the outside air or making your home damp.  

Your crawl space should be dry; a usable space that adds value to your home. It MUST NOT be a space for mold, mildew, and pests to create havoc — in your home and your life.

Read more: Tips on carefully insulating an old home

A Concise Guide on Crawl Space Insulation was last modified: December 20th, 2022 by Ramona Sinha
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