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Should I Insulate the Crawl Space?

Crawl Space Insulation is Key to Energy Efficiency

When I meet with clients to discuss working on their crawl space, the question of whether or not to insulate the crawl space is always a topic of discussion.

If they have met with other crawl space encapsulation contractors there is normally a look of too much information and even distrust on their faces because they called three different companies and got three different answers about what to do in their crawl space.

I can't address all the crawl space confusion in this article but I would like to discuss crawl space insulation and whether you should or shouldn't insulate your crawl space.

The short answer is YES you should insulate your crawl space IF you want to make your home MORE energy efficient. So, why do so many homeowners tell me that the last crawl space waterproofing company said they don't need insulation? I think the key to that is the use of the word "need".

If you think about it, you don't need attic insulation either. Of course, it is local code that you have it during the building of your home but if you have an older home with inferior insulation to today's standards no one will come and inspect your attic.

The Department of Energy recommends that you have a properly insulated crawl space. So what does that mean?

The way you insulate your crawl space is determined by many factors. If your winters are harsh and there is low humidity where you live the insulation you choose is different versus a very humid climate with milder winters and hotter summers.

Since I am located in Tennessee I will be discussing types of insulation and insulation R values for the Southeast.

Types of Crawl Space Insulation

We mainly use three types of insulation when it comes to crawl space insulation in the south.

  1. Fiberglass Insulation
  2. Foam Board Insulation
  3. Spray Foam Insulation

Please understand there are many types of insulation and even sub types within the types of insulation I listed above. For example, in the fiberglass insulation category there is batt insulation, unfaced insulation, faced insulation, foil faced insulation and even mineral wool insulation which is not fiberglass but is comparable.

Most homes in the Southeast especially Tennessee have been built with these types of insulation.

Foam board insulation and spray foam insulation are becoming more popular especially with the introduction of crawl space encapsulation. Both types of insulation will work in a crawl space with a vapor barrier as long as certain  project and all three types will work with a vented crawl space depending on where the insulation is applied.

When deciding whether to insulate or not, here are some factors to consider:

Type of crawl space: vented (open) versus non-vented (closed)

  • Height of crawl space
  • Climate
  • Budget
  • Access size
  • Square footage
  • Time in home
  • Return on Investment
  • Comfort
  • Air Quality

Let's look at crawl space height. If your crawl space is really short or really tall the type of insulation you choose will vary. Foundation insulation may not be cost effective on a crawl space with twelve to sixteen foot walls or walls that are extremely short and difficult to get to. Also, if the door access is small this can hinder the type of insulation used.

About Michael Church

Michael Church has been involved with indoor air quality since 2005 and feels the unhealthy crawl space is one of the major problems causing poor indoor air quality.

9 Comments

  1. Keven on June 6, 2018 at 2:56 pm

    Hi Michael,

    My new encapsulated crawlspace has nine mil vapor barrier on the ground plus “curtained” pieces hanging down the walls and taped to the ground piece.

    How can I insulate with foam board? Is it ok to attach the foam board on top of the vapor barrier on the wall or do I have to cut the seam, lift the wall vapor barrier pieces and insert foam board behind?

    Thanks

    • Michael Church on June 16, 2018 at 10:20 am

      Great question – you can install foam board insulation over the vapor barrier but keep in mind if you puncture the vapor barrier, it may leach moisture through.

  2. Tim on June 16, 2018 at 7:26 am

    Where can you get the termite resistant crawl space insulation?

    • Michael Church on June 16, 2018 at 10:17 am

      Hello, we offer the foam board at $34.99 + tax for R-10 4×8 sheets but we don’t offer shipping so it must be picked up. Hope that helps. You can call our office (865) 659-0390 if you’d like to place an order.

  3. Patrick Martin on February 4, 2021 at 11:53 am

    I have a crawl space t j.g at gas a good moisture barrier in it , just got installed , fogged it with sporcieden, ran blows to dry it out for a couple days . Then paid guys to insulate the floor with faced r19 .
    Except they f as vmced the paper down . I also have 2 fans on timers oscillating the air under the house. From noon till 5 every day. Its a double wide . Do we gave to flip the insulation beings we have a taped and glued 10mm liner . Glued to walls and on seems , taped too even on pylons .

  4. Kyle C on November 15, 2022 at 5:27 pm

    We live in a dry and cold climate (Utah) and have our crawlspace walls (above the concrete, below the floor joists) insulated with fiberglass batts, and a vapor barrier on the bottom. Since the crawlspace is technically already insulated, would it be worth it to add R-19 fiberglass batts in between all the floor joists? I would like to keep our first floor warmer in the winter, but would it really make enough of a difference since there is already some insulation down there?

    • Michael Church on November 23, 2022 at 4:41 pm

      Hi Kyle, great question and I wish I had a definitive answer but insulation only works if there is a heat source present. If your home heat is losing air in the crawl space and may be heating the crawl space a little, insulation could hinder that heat from warming the flooring. If there is not heat source in the crawl space then new subfloor insulation could prevent the living space heat from transferring and being lost to the crawl space. One last thing I will say is the floors will never feel warm unless something is heating the floors. Granted they could feel warmer with insulation. Hopefully that answer helps.

      • Kirk Andree on December 3, 2022 at 12:49 pm

        Hi Michael, I’m having my crawl space insulated as we speak. I have an 80 year old red brick home in Reno NV. The crawl space is only under the 3 exterior wall living room.
        The rest of the home has a basement that is all built out. I have a moisture barrier on the dirt and I’m putting R15 faced batts between the joists. To heat the living room I have a gas insert fireplace along with a gas forced air hvac. Is this going to help keep the oak wood floor warmer? Thanks.

        • Michael Church on December 14, 2022 at 3:32 pm

          Hi Kirk, batt insulation is pretty effective in an open or closed crawl space when it comes to assisting in trapping heat to heat the home. Just keep in mind, floors will be warmer but not warm without the addition of heated floors. Hope that helps.

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