How to Insulate the Crawl Space Under Your Home

Man in white jumpsuit adding insulation between joists in crawlspace under house.
Adding insulation between joists in crawlspace under house.

My house has a crawlspace under it, and the floors get very cold in winter. What is the best way to insulate a crawlspace on a budget? -Margaret

Hi Margaret,

Having a crawl space under your house can make your home colder in the winter than a house built on a concrete slab. Also, mold and mildew can be a problem in a crawl space, so you need to be sure to guard against that as well.

To make the floors in your home warmer, and prevent mold and mildew from forming in the crawl space, requires more than just insulation. Here’s how to go about reducing moisture and insulating a crawl space under your home:

  • Cover Ground: Start by removing any items stored under your house, as well as any construction debris, such as scraps of wood or broken bricks. Next, even out the dirt in the crawl space, and correct any problems you might have with water standing under your house by filling in any holes or depressions. Finally, cover the entire area under the house with a layer of 6-mil plastic sheeting. Overlap the sheets a foot or so, cut the plastic around piers, and run the plastic all the way to the foundation walls. As an added measure, you can tape the seams in the sheets together to keep the plastic in place.
  • Insulate Under Floor: Fiberglass insulation batts or rolls are the most economical and easiest DIY choice for insulating between the floor joist in a crawl space. The U.S. Department of Energy recommends R-11 (3½”) insulation under floors in warm climates and an R-25 (6” to 8”) in cold climates. Install the insulation with the paper vapor barrier facing up toward the heated living space, and make sure the insulation fits tightly between the joists. Hold the insulation in place from below using insulation support wires, or by stapling chicken wire to the bottom of the joists.
  • Enclose Foundation: If your foundation isn’t enclosed, fill the space between the exterior piers with bricks, concrete blocks, or lattice panels. To install brick or block walls, pour a concrete footing between each of the piers around the outside of the house, then lay bricks or blocks on the footing. Install foundation vents in the walls, so there is one-square-foot of vent space for every 150 square feet of crawl space. Another option is to make 2×4 frames from pressure treated wood to fit between the piers; then cover the outside with lattice, and staple landscape fabric on the inside to reduce (but not stop) air infiltration under the house.

Good luck with your project,


Further Information


  1. I have a new addition on my house. The footing walls in the addition have been insulated with spray foam. Now I have vapour barrier and rigid foam insulation to complete the ground. What order do they go down and should attach anything to the walls?

  2. What is the Tennessee code for having paper backed vs no paper back Batt insulation inbetween joist up against flooring. I have heard the code changed to no paper backing due to moisture collection issues.

  3. During a recent termite inspection, the agent mentioned that I have severe mold on the insulation and on the floor joists ( i had noticed it also during my last trip under the house). He recommened ripping out the insulation, treating the wood and laying down a new layer of 6 mil plastic. He also said not to bother replacing the insulation as it wasn’t cost effective. Is that right?, not to bother with insulation, it would cost an extra $2500 to replace.

  4. I am insulating crawl space in Louisiana of a 1880’s house. House is 7 ft off of the ground. We are using batts. in the past I have used visquin and stabled it in between the joist to help hold the insulation in place. The contractor told me not to due this because it will cause moisture build up. I have done this in the past with no problem. I have had problems with chicken wire…it rust and is hard to work with if you need to get in to do work. The contractor wans to use a nylon cloth that looks like the material used under the bottom of chairs….Suggestions

    • Hi Darryl,
      You should use a material that allows air to go through, such as landscape fabric, to prevent moisture build up. Or use spring rods every few feet that are made for such a purpose.
      Thank you for your interest!

    • Darryl, did you use faced or unfaced insulation? I have a similar situation in Lafayette, but my home is about 2 ft off the ground. Thanks

  5. 1st things people always ask me the rotation of ceiling fan in winter and summer.I tell them that in the winter time the ceiling fan rotation standing under it while looking straight up at the fan the blades should be going in a ccw direction and in summer the blades shouold be cw while being directly under fan and looking up.People really have an issue being able to decide rotation because they see videos like on youtube and some people are looking at the fan in a direction that communicates to certain people a different angle or look and it confuses people on the exact rotation.I am correct aren’t i?Please respond so i can ensure people i have told them correctly.And on the floor insulation r11(rolled batts) the paper is suppose to be on the bottom side. Is this correct like you do on a wall inside of your house?I have other questions but i will do them in another subject line later.Thank you so much for a response…A loyal customer!!

    • Hi Walter,
      When looking up, ceiling fans should turn counterclockwise in summer and clockwise in winter. See our article on How to Use a Paddle Ceiling Fan Properly at to find out more. On insulation, the paper should always face toward the heated (interior) of your house. So under a floor the paper would face up, in the attic down, and in walls toward the inside.

  6. Hi Danny I am confused my house is on piers built 1955 I have plastic laid on ground but want to insulate because I have hardwood floors an can feel drafts I have rugs on most floors but still cold will insulation help faced or unfaced I need a budget friendly solution thank you lela ann Marlow I miss your show every week see you when football goes way I live in saraland al 36571

  7. Has anyone have any comments on the yea or nay of spraying the concrete blocks on the inside to improve insulating the craw space. can you forget about the batten insulating between the floor joist

  8. I had professional house movers come out and inspect my 1928 house crawl space and this is what they told me: ( they are excellent and I have known them for a long time) If your home sets low to the ground on original foundation, it is best NOT to put insulation under the house!!The insulation will hold in the moisture and rot out your subfloor etc.They said many home owners make this mistake and it ruins their foundations in older homes.

    Recommendations for older homes:
    1. remove any insulation that you have placed under the house
    2. seal underneath with plastic
    3. install one or two humidifiers as needed
    4. Must have gutters on home that work well to keep any additional water from getting under house

    Your home should last for many years without any additional destruction to the sub floor or joist.

  9. After installing the insulation, 6mil plastic on the dirt floor of a 5′ dirt filled crawl space, I read an article that said to put 6 mil plastic over the ceiling insulation as well. Is this okay to do as well for added protection

    • Hi Jim,
      I’m not sure what you mean by ceiling insulation. If you’re referring to putting plastic sheeting over the bottom of the floor joists in the crawlspace, you shouldn’t as it will act as a vapor barrier and trap moisture from the house in the floor joists. If you want to put something on the bottom of the joists to hold the insulation in place, use chicken wire, landscape fabric, or housewrap so any water vapor from inside the house can escape. If you’re referring to insulation in an attic, you shouldn’t put plastic sheeting over the top of it either for the same reason.

  10. I own a 28×70 home. I had batt insulation between the floor joist under my house twice. Had to have th first insulation torn out and replaced because of mice nesting and raising young in it.For the second time now, I am. Having it torn out because of mice nesting in it, the stinch smells like a sewer. I have set traps and other methods, almost no success. I considered having spray foam insulation sprayed between floor joist this time around. I talked with 2 guys who do this type of insulation. But I did some research of my own and found that if the chemicals aren’t properly there can be off gasing leaving harmful odor throughout the home causing homeowners to vacate their home. Some say they don’t know if it will ever be possible to return home again because of the off gasing from the spray foam insulation. It did not cure properly. My home sets lower to the ground under the back of the house and much higher in front. we live upon a hill side, the ground underneath the house slants downward as you move toward the front of the house underneath. I am so desperate at this point I have been in tears for days trying to figure out the best options to solve all these problems. I cannot not afford to rebuild. Please help if you can. I need all the advice I can get at this point. I am literally in despair. What do I do, is there anyone who can help my situation and circumstances or is this hopeless?
    Please I need help

  11. I have a new home in Durham, NC. This winter I was awoken many times by a loud shreak. My hardwood floors on my first floor were heaving and separating. I could actually roll a 50 cent piece down one of the cracks between the red oak slats. The floor was cold to walk on all winter, had to wear thermal socks. The builder says that NC code is an R-value 19, which it is, but this crawl space has a ceiling height of 6 feet. I can walk under my entire house. Does R-19 really suffice, especially giving the hardwood separation and heaving?

  12. Thanks for the suggestions, Danny. I am in temperate Melbourne, Australia and will be looking into the steps you suggested for Margaret.

    You run a great website.

  13. We live in a house on poles which has an open entertainment area downstairs. What can I use to insulate the ceiling. We have hardwood floors upstairs which get really cold in winter. We are in Queensland, Australia

  14. I am not sure why a lot of folks recommend using bats when after a few years it starts to rot and fall apart. Is there not a spray foam that could do the job? I am also looking at double bubble however have not heard of anyone using it.

      • Thanks for sharing your experience with the Today’s Homeowner community, Evelyn!
        TH community members helping other TH community members — we love it. 🙂

  15. Great information here! I had tried a few things, actually some on the list, in keeping moisture from my crawl space from entering my home. I ended up having a local service here in Michigan come out and fully encapsulate my crawl space. Nothing could possible have worked better. I’d definitely recommend looking into it. However, in the meantime, there are some great tips listed here in this article.

  16. I have a brick rental home not on a slab and crawlspace is 8 inches to 13 inches unless interior floor is torn out can’t get anyone underneath.I have had to replace total floors due to moisture damage and floors caving in..more than 3 times this last time I brought treated plywood..and the interior floor has moisture under the rug in kitchen area hallway and bath..please help..

  17. I was thinking about using foam in between my floor joist under the house where i have about a 3 ft crawl space that has a lot of moisture. I was also going to put 6 ml plastic on the ground like was suggested.
    What do you think?

  18. I have a house in the poconos. I want to know what is the proper way to insulate and heat the area. It is 40×25 and about 5′ in height. Right now I have r-25 insulation with a orange mesh to keep it up. I have a heater and a dehumidifier. Seven blocks are open with vents . In the winter time I put styrofoam in the opening and put the thermostat on 50. The ground does not have 6 mil plastic. Can you guide me in the right direction.

  19. I’m looking to put brick under my house to keep any animals from getting under my crawlspace. Who could I contact about doing this?

  20. Help in Montana .My home is 5 months old. This winter it was colder than usual 20- with wind chill 30 to40 -below . Between the floor joists where the header board is on the outside it was sprayed with foam, the crawl space has an open vent so air will circulate in the crawl space and a vent into the basement to draw air out. I found moisture on the sprayed in foam and water sitting on the sill plate . I need a fix ? What ever you say will help.
    Thank you,

  21. This is what I did to my crawl space here in Northern Canada where winter can get -30 that’s cold. First I took out all the Batt insulation because it a mice bed and it can collect moisture and start to stink like old sawdust then it will start to rot your floor joist out. Secondly I installed one and a half inch thick rigid foam on the concrete blocks inside the basement with the use of pl300 glue for foam and tape the joints. I used cheaper durafoam ( green and silver colour.) then I place a blue tarp over the gravel floor and tape the seams to the wall rigid foam and to the overlap centers on the tarps. I also taped the post pier that holds up the center beam of the home. Then I cut 15“long x 8“ wide pieces of foam for the joist sill opening between the joist and use a few cans of spray foam were I notice gaps around the pieces. Then I put 3 heat ducks in the basement ….. Now my floor is warm and my water pipes will not freezzze. In the summer months I have to small basement opening I place screen windows and remove plywood which I putin in the winter.

  22. I need to insulate my crawl space. House is elevated from 1 to 3 feet. Brick foundation with vents.
    Hard wood floors with no under layment. Built in 1930. I don’t know if I should use batt insulation or ridgid foam sheets. I only want to do it once.
    Pros and cons of both if you can help.

  23. I have a crawl space. I layed plastic on the dirt floor. I put 12 mm laminate floor through out the house including closets. I put the best underlayment between the sub floor and the new laminate. I caulked between the floor ends where it meets the wall.
    The house is much warmer and more quiet. And no mold in the crawlspace.

  24. Our home is 2 years old, our craw space is 6’ H x 14’ W x 50’ L, they foam sprayed the exterior walls, but they not put anything between the floor joist and my floor is cold ?

  25. Hi, I have a old home with wood floors and nothing under them. My crawl space is 24 to 30 inches.This old house is so cold in winter, the floors are very cold. How can i insulate under my home to make it warmer. I need help please. Thanks in advance.

  26. I have a craw space that is molded due to moisture trapped underneath. I’m thinking of putting foam insulation under the main floor to keep the house warm and the moisture out. Is this sufficient to keep the winter cold out or is there another alternative?

    • Hi, Teresa,
      Danny says, “Foam sheeting will work okay. A better alternative would be mineral wool insulation or Rockwool.
      Also, make sure you have a sheet of plastic laying on the ground to serve as a moisture barrier.
      Thanks for your question, and good luck!”

  27. Danny pls help! We are a young couple with 2 small children. Bought.older home and remodeled. Put in laminate floor. Floor started buckling. The house sits low to ground. How do we fix it.

    • Hi, Cam and Tim! We’re always looking for homeowners to call into our radio show and ask questions directly to Danny and Joe. We’ve reviewed your question and shared it with our radio show’s producer.
      Thanks for writing! 🙂


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