If you want to keep home warm at all times, you should insulate your crawl space. Crawl space insulation is crucial for keeping your home warm; it can also prevent your crawl space from getting moist and harboring mildew and mold.

How do you know when it’s time to insulate your crawl space? If you have cold feet even when your furnace is up, you might need to check your crawlspace. If your house was built before the energy-conserving building codes were standardized in 1990, your home might have no installation at all.

To keep things warm underfoot, you have to try crawl space insulation and seal all air leaks. By insulating, HVAC ducts and plumbing pipes are protected from freezing temps, helping to conserve energy.

Crawl Space insulation|How To Insulate Properly & Happy

Things To Know Before You Start Insulating Your Space

Support. Fiberglass batts should be installed and unfaced so that they make contact with the underside of the subfloor. Avoid tension rods; they compress the fiberglass, reduces its insulation value, and can get loose. A crisscross webbing of wire will provide the best fiberglass batts support.

Seal the subfloor and insulation. Ensure that the holes used for plumbing and electrical wiring are sealed with spray foam insulation. Avoid open open-cell spray insulation as it soaks up moisture like a sponge. You should also insulate HVAC ducts and plumbing pipes to avoid freezing and heat loss.

Ventilation. Your insulation contractor will calculate the amount of ventilation your crawl space needs and cut in new vents as required.

Note: Avoid stapling fiberglass batts between joists to the underside of your subfloor. Although using that method can work for the short term, moisture will eventually build in the crawl space and grow on the surface. Then the moisture-laden fiberglass will become heavy and start to sag and fall.

Instead of stapling fiberglass batts between joists to insulate, you can apply the multi-pronged method of insulating the crawl spaces inside walls with rigid foam, laying down a plastic vapor barrier over the floor, and joining the two items with tape. This method costs about $5 per square foot for professional installation, which includes materials. Although it might seem expensive, it offers a permanent solution. However, you can do the insulation yourself for half the cost, but it takes time and lots of effort.

Types Of Insulation

Rigid foam insulation. This type of insulation is an ideal type of insulation for crawl space inside walls. It works for any wall, including concrete, block, stone, and even brick.

This type of insulation is faced with a silver foil facing inward towards the crawl space. Although the rigid foam is the chief insulator, the foil acts as a vapor barrier and also add some more energy savings by reflecting the heat into the crawl space.

Crawl Space ventilation. With this insulation, the crawl space ventilation to the exterior is all sealed off with caulk. Once you have an insulated crawl space, your house will become more energy-efficient by keeping your floors warmer during cold seasons and reduces your heating bills. The good thing about insulating your crawl space is that your floor is also cooler during the warm months, which reduces the load on your AC (Air Conditioner).

How To DIY Crawl Space Ventilation

How To DIY Crawl Space Ventilation

Things you’ll need

  • Fine-toothed saw
  • Caulking gun
  • Utility knife
  • Flashlight
  • Rake and shovel
  • Poly PVC tape
  • Foam insulation
  • Silicone Caulk
  • Construction adhesive
  • Double-sided butyl tape
  • Latex adhesive for foam board
  • Expanded polystyrene foam board
  • 6-mil minimum thickness clear polyethylene plastic


Step 1: Access your crawl space and locate any moisture that collects in that area. With your rake and shovel, regrade soil banked up outside of your home so water moves away from the structure.

Step 2:

  • Don’t focus on your crawl space alone; check your within the house for the source of moisture.
  • When you’re inside your crawl space, shine a flashlight around the underside of your home and look for water dripping down.
  • Look at the pipes running within or through the joists.
  • Pay close attention to the floors above bathtubs, showers, sinks, and dishwashers to ensure that there isn’t built-up moisture.

Step 3: Seal up any doors, vents, or hatches that links from the outside of your homes into the crawl space. Use the caulking gun to insert caulk into holes and cracks.

Step 4: Check out your crawl space during the day to make sure there aren’t any cracks and holes. Turn off your flashlight and examine the rim joints and sill areas to ensure no light is shining through. If there is, turn on your flashlight and seal up the cracks with your silicone caulk. If the cracks are large, you can use your low-expansion foam insulation.

Step 5: Cut the rigid foam pieces into small sizes with a saw and attach the pieces to the inside crawl space walls with the latex adhesive. You should aim for little seams as possible by installing large sheets of rigid foam. After you’re done with that, seal seams within the boards with PVC tape.

Step 6:

  • Lay down the vapor barrier on the crawl space ground area.
  • Make cutouts for every piers and post.
  • Run the vapor barrier against the piers and posts and seal them tightly with a butyl tape.
  • Seal the seams between different vapor barrier sheets.
  • Finish up by running the vapor barrier about 12 inches up the insulated walls and taping the insulation’s edges.


By insulating your crawl space, it can be linked to your household HVAC systems through vents. That way, warm air will keep circulating under your floors to keep you warm during cold seasons.


  • Dave Toht. Houselogic by Realtors. How to Insulate a Crawl Space. 2020. [https://www.houselogic.com/organize-maintain/diy-repair/insulating-crawl-space/]. Accessed by 27th of October 2020.
  • Lee Wallender. The Spruce. How to Insulate a Crawl Space. 2020. [https://www.houselogic.com/organize-maintain/diy-repair/insulating-crawl-space/]. Accessed by 27th of October 2020.
  • Joe Provey and Bob Villa. Bobvila. Top Tips for Insulating Crawl Space. [https://www.bobvila.com/articles/insulating-crawl-space/]. Accessed by 27th of October 2020.