Do You Need Crawl Space Insulation?

What is crawl space insulation? And do you need it in your home?

Insulation in the crawl space that has been properly installed is an essential part of the building envelope. The building envelope includes outer walls, roof, window, and door frames. They contribute to improved air quality, reduced temperature fluctuations in your home, and efficient use of energy.

Crawl Space Defined

A crawl space foundation is when the first floor of a house is raised about 1-3 feet above the ground. The crawl space floor could be dirt alone, or it could be overlaid in gravel or plastic sheeting to act as a vapor barrier to keep moisture out of the area and safeguard your home from mold and moisture damage.

Common Crawl Space Insulation Snags

Here are some of the more frequent crawlspace insulation problems that homeowners encounter.

  • To prevent ground moisture, irrigation water, and drainage water leaking into your crawl space, a vapor barrier must be properly installed.
  • Falling insulation indicates that your crawlspace insulation is no longer performing properly. You will need the services of a professional insulation removal company to remove and restore any damaged insulation.
  • Mold and mildew in your crawlspace not only produce a musty odor, but can also create health problems.
  • Bugs and rodents in an attic or crawlspace can cause structural damage, holes, damaged insulation, etc. Consequently, rodent entry points need to be located and sealed off and ongoing monitoring is highly recommended. 

Why is Insulation Necessary?

Crawl space insulation that is properly installed and maintained will:

  • Improve your home’s energy efficiency.
  • Cool your home on hot days and keep it warmer on cold days. 
  • Improve your home’s air quality.

Crawl Space That’s Vented

Air vents in vented crawl areas exchange air passively with the outside. The air is unconditioned in a vented crawl space. Insulation is typically installed between the floor joists beneath the sub-floor. This means that all of the air above the insulation in the crawl space is conditioned.

Adequate ventilation is important to remove excess moisture from the crawlspace. A properly installed vapor barrier will also prevent moisture from the soil entering the crawlspace which could lead to mold growth and rot. Further, it is important that the subfloor, heat ducts and water pipes are covered with insulation to prevent heat loss or condensation. 

Crawl Space That’s Unvented

In this case, a moisture barrier is laid along the ground in an unvented crawl area to prevent moisture from the soil entering the crawlspace. The crawlspace foundation walls are insulated, but the subfloor is not. By design, this kind of insulation extends the building envelope downward to include the crawl space in the home’s conditioned space.

Unvented crawl spaces provide the following distinct advantages over vented crawl spaces:

  • Improved moisture control
  • Improved indoor air quality
  • Increased energy efficiency
  • Less temperature fluctuation

Call the Professionals at American Crawl Space

  • If you’ve been ignoring your crawl space wall insulation, you might consider hiring an insulation contractor to perform a thorough assessment.
  • If you intend installing new crawl space insulation, make sure it’s done by professionals to guarantee correct insulating measures are implemented.

Having insulation professionally done in your crawl space ensures that there are no air spaces that allow moisture to flow upward. Of course, this will extend the life of your home and result in better air quality and energy efficiency.

Furthermore, you may require crawl space cleaning before proceeding with the insulation process to help remove mold, waterlogged insulation, or old fiberglass insulation, giving you a clean slate to work with.


In summary, if your property has a crawl space, consider having it professionally evaluated by our American Crawl Space experts.

Contact us today to learn more about crawl space insulation, repair, or to receive an expert evaluation on the status of your Seattle-area home!