Is Crawl Space Insulation Required?

Is crawl space insulation required? Many homeowners are confused because contractors are telling them it is not necessary. Why would a contractor say something is not required when building code says it is?

International residential building code requires a crawl space to be insulated. If the crawl space is open or vented, it needs to be insulated. If the crawl space is encapsulated, it needs to be insulated.

We take the crawl space insulation a step further. Crawl spaces are great sources of drafts into the living space. Because of the indoor air quality and drafts, we recommend the crawl space be air sealed too. Air sealing and insulating your crawl space properly will improve the health of your home. It will also improve the energy efficiency, thereby lowering your utility bills.

Crawl Space Insulation R-Value

What is R-value? RValue is the rating system used to grade insulation products or a material’s insulating properties. The “R” stands for “resistance” and refers to the resistance a material has to heat flow, or temperature conduction. The R-value required in your crawl space will depend on your climate and local codes. In East Tennessee and much of the south, R-10 is used on foundation walls of crawl spaces. R-19 is used between floor joists of crawl spaces.

Crawl space insulation is required which is why homebuilders install insulation in the crawl space. If the home is built without crawl space insulation, the code enforcement officer would not give the home a pass on the inspection. If code enforcement requires insulation, why do crawl space contractors remove it and not reinstall insulation? Check your local code enforcement for the R-value requirement in your area.

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8 thoughts on “Is Crawl Space Insulation Required?”

  1. Hi Michael

    Thanks so much.
    I live in an area that tends to be humid in the
    summertime. I currently have a vented crawl space ( it is really 2 crawl spaces bc of an addition put on before I got the house) .There is insulation on ceilings, a sump pump and vapor barrier that is okayyy but not adequate bc spots exist where you can see the ground. I do get water under there which is pumped out by sump. It still gets damp under there and which to encapsulate. There are wee little white dots of what I believe is mold in the back( 2nd) crawl space. The foundation is cinder block. Between the two crawl spaces is wall of conder block which has very small opening for some wiring. So do you think I will need two dehumidifiers and two vent fans? I will need to get rid of the ceiling insulation and get foam board insulation for walls instead? Is it ok to put new vapor barrier directly on dirt w no pebbles underneath ( the pebbles was a suggestion from one contractor , but dont want vapor barrier to be torn which could happen by HVAC maint guys or plumber, etc.
    The entire home is only 1400 sq feet…. Yet the two crawl spaces. I sure do wish you guys were up in Northern VA!!
    Thank you in advance for any advice

    1. Hi Mary, if the holes in the wall between the 2 crawl spaces do not allow adequate air flow and they cannot be opened up to allow adequate airflow then I would treat them as 2 separate crawl spaces and have 1 dehumidifier, 1 fan, 1 sump pump in each. You can replace the subfloor insulation with wall insulation, my preference, but technically subfloor insulation is ok too but it can trap moisture. If you do wall insulation you only need to insulate the exterior walls not the one between the crawl spaces. Vapor barrier directly on dirt is my preference as well if there is nothing that can puncture it and it doesn’t have a lot of traffic or used as storage. Not sure what pebbles will accomplish, did they say why they recommend pebbles on dirt covered with plastic? Thank you for your kind words, I hope we will have a franchise in your area one day too. I hope this information helps you.

  2. Nelson Buchanan

    Hi Michael,
    Would I be able to add insulation after my crawl space has been encapsulated?

  3. Our open or vented 1500 sqft crawl space has old batt insulation that has fallen here and there. The metal hangers rusty and lying everywhere. Ten mil poly covers the dirt. But extensive HVAC duct work makes it a challenge to move around and get to every corner. Our pest control company advises we remove all the failed insulation between joists and replace with encapsulated batt insulation and corrosion resistant hangers. Our climate zone is 8B. What do you recommend is the best approach for us?

    1. I am not sure that corrects what caused the rusted hangers and falling insulation. My apologies but where is 8B? Is that Canada? If you did as they said, it sounds like there was moisture at some time to cause the issues you are correcting. Has the moisture problem been addressed? If not, the encapsulated batts are not air sealed and will allow moisture to enter.

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