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Crawl Space Encapsulation Vent Fan

Are you asking if a vent fan is needed when encapsulating your crawl space? In this article we explain what we recommend per EPA guidelines when it comes to crawl space ventilation.


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Foundation Vent Fan

The foundation vent fan is a concept pretty unique when it comes to building practices. Similar to attic ventilation, it is often overlooked and misunderstood. Many homeowners hear conflicting information from pest control and waterproofing companies about crawl space encapsulation vent fans.

Most foundation vent fans are constructed of plastic or metal. Many use computer style fans to move around 100 cubic feet per minute of air. Some place the fan to draw air into the crawl space. Some homeowners have the crawl space air being pushed out.

Whether your fan is pulling in outside air or pushing it out, the effect is pretty much the same in an open or vented crawl space. The make-up air is still being pulled from the air outside.

Vent Fan image

Open Crawl Space Vent Fan

Is having outside air enter your crawl space a bad thing? That depends on the humidity level of the make-up air. If you have an open crawl space in Knoxville, TN or Atlanta, GA chances are you are bringing in hot humid air.

Hot humid air hitting cold, poorly insulated and non-sealed duct-work is a recipe for mold and wood rot fungus. Mold and fungus can affect the sub-floor and cost you money in foundation repairs and floor stabilization.

Perhaps a vented crawl space in Denver, CO or Las Vegas, NV is not that much of an issue in regards to humidity. If the same principle applies with cold ducts in the crawl space, the hot non-humid air can still rob your home of air conditioning.

Using a Vent Fan with Encapsulation

This is where many get confused. For years, crawl space contractors have been sealing all the vents during encapsulation. In fact, many home builders create homes without foundation vents.

Why the drastic change? Research has shown an encapsulated crawl space has less mold, structural issues, and critters than an open crawl space. This doesn't mean all builders are closing crawl spaces but some won't build a vented crawl space.

The problem is soil gases. The crawl space companies and builders that close crawl spaces have created a problem while trying to fix others. When you seal all vents or build with no vents, the soil gases' only route is in your home.

Read our last article:

Crawl Space Encapsulation Dehumidifier


Vented crawl spaces certainly create more mold and structural problems. But, they allow nasty and potentially deadly soil gases to escape.

Installing a vent fan and performing crawl space encapsulation is the best scenario to address both problems. But there is another problem. Many contractors and builders do not include a dehumidifier.

That's like creating a well-insulated home with no heat source or air conditioner. No matter how good the crawl space is encapsulated, humidity, and other moisture problems still find a way to exist.

Crawl Space Encapsulation EPA Guidelines

I actually stumbled across the EPA (Environmental Protection Agency) guidelines by accident. I was researching open vented crawl spaces versus crawl space encapsulation and shocked at what I found.

I find it absolutely appalling that Crawl Space Ninja is one of if not the only company including ventilation and encapsulation.

The EPA says to install a foundation vent fan that will move 1 CFM of air for every 50 square feet of crawl space.

Did you know that? Did the last company that quoted your job tell you that? What about local codes enforcement, do they know what the CFM per square feet rating is?

This is why we look at your crawl space as a whole and try to make it worry-free. We are not just interested in the vapor barrier or a french drain. We don't remove mold without fixing its cause. Insulation and air sealing are not overlooked in crawl space encapsulation either.

When you hire Crawl Space Ninja, we explain how to fix the entire crawl space not just cover up or delay problems. This doesn't mean all homeowners follow or even like our advice. But that's not going to stop us from proposing the worry-free crawl space solution for your family.

Contact Crawl Space Ninja for Basement Waterproofing and Encapsulation

Please contact us to schedule your assessment to fix your crawl space, basement issue. 


Do you need help with mold removal, crawl space encapsulation, crawl space insulation, vapor barrier, waterproofing, foundation repair, basement waterproofing, or controlling humidity in your crawl space?

If you live in Georgia, Delaware, North Carolina, South Carolina, Tennessee, or Kentucky, Crawl Space Ninja can help!


Also, let us know in the comments below if you have an idea for a new blog topic.

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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.


  1. John brabo on December 15, 2020 at 7:39 pm

    Can you recommend any contractors in the sacramento region?

    • Michael Church on December 16, 2020 at 10:03 am

      I am so sorry John, we do not know of anyone in that area.

      • B. Watkins on July 2, 2022 at 1:02 pm

        I have a vent off the furnace that leads to the outside. Is that good enough in my encapsulated crawl space.

        • B. Watkins on July 2, 2022 at 1:13 pm

          Forgot to say that I live in Colorado. Wondering if my furnace vent to the outside is good enough to vent my encapsulated crawl space.

          • Michael Church on July 8, 2022 at 11:13 am

            Hello, it sounds like it would be ok but you may want to consult local HVAC company just to be sure.

  2. Bryan on December 31, 2020 at 11:11 pm

    I’m a home builder in Tennesse area which we encapsulate all of our crawlspaces for all the reasons we agree with you on. We also put in the radon mitigation piping that’s under the crawlspace poly and exits through the roof. We are wanting to follow epa exhaust guidelines on encapsulated crawlspaces and wanted to know if installing a radon fan would be sufficient in meeting the 1 cfm for 50’ of crawlspace. . This assumes all calculations match up. In the end, just looking to install one fan and resolve two issues with soil gases and radon prevention. Thanks and really enjoy your detailed information

    • Michael Church on January 4, 2021 at 2:01 pm

      Hi Bryan, great question and from what I understand about how they write the requirement, your way of installing a sub-membrane depressurization system is sufficient and should not require the fan in the foundation vent. Thank you, hope that helps.

  3. Ralph R. on February 8, 2021 at 8:56 pm

    I just had a full encapsulation, but another company with similar products, since Crawl Space Ninja doesn’t service me area. Well when I asked about the vent fan, they indicated that it was not needed nor a service they provide. I didn’t take measurements before hand, but my radon level is hitting around a 4.0 pCi/l peak with 3.5 48 hour average. Is this an crawl space vent issue or a radon mitigation service issue? I am think I will have to DIY install the vent fan to pull the air out and monitor for a few days.

  4. Ali Cameron on April 18, 2021 at 11:30 am

    We just had our crawlspace encapsulated with 12 mil poly. It goes up to the sill plate and the exterior walls are insulated with 12 R value foam board. The only 4 vents we had in the foundation walls were covered. We installed a sump pump and a Moisture Medic 90 (Aprilaire) dehumidifier. The crawlspace is approximately 1325 square feet. It’s one big open space with concrete block footings down the center of the home. My question is do we need to have an exhaust fan venting air out of the crawlspace through the foundation and a vent from HVAC system installed pulling air through the crawlspace or is the air circulating from the air movement of the dehumidifier enough? Someone suggested putting a box fan down there on a timer to circulate the air around a couple times a day. It just seems odd to be all sealed and virtually no air movement or a way for the seemingly “trapped air” to escape.
    All HVAC ductwork was insulated too at the time this was done. This was all done after mold remediation took place.

    • Michael Church on April 26, 2021 at 12:59 pm

      According to EPA guidelines you should exhaust 1CFM of air for every 50sq feet of crawl space to the outside air. Normally a Lomanco PCV1 fan is enough to accomplish this. Here is a link: https://diy.crawlspaceninja.com/fans/ Hope that helps.

  5. Chuck Davis on April 18, 2021 at 11:03 pm

    Good information and video. Thanks. Exhausting air from an encapsulated crawlspace does seem to be something that has been overlooked.

    We had our crawlspace in Durham, NC encapsulated with spray foam. Ducts and registers were sealed. The crawlspace is *really* tight.

    A 400 CFM inducer was installed in the HVAC. No dehumidifier. RH peaks at around 70% in summer, drops to 45%-55% in fall/winter/spring.

    There is a 4″ drain that connects through the foundation to a 6″ collector on the footer with about a 75 foot run to an outfall, but I’m not sure how much air flow/pressure relief this provides. (I could probably run a flame test.)

    What would be your thoughts on a passive exhaust vent in the crawlspace door vs. dehumidifier vs. leaving as is?


    • Michael Church on April 26, 2021 at 1:02 pm

      A dehumidifier is the best way to control humidity in our experience. Exhaust fans in humid environments do little to control humidity. If your humidity spikes above 55% I would not leave as is. Thank you and hope that helps.

  6. Aaron Buchanan on August 11, 2021 at 10:38 pm

    So do these foundation vents fans run 24/7 or do they cycle on? Do they make the dehumidifier work harder since now longer sealed from the outside environment, I guess if they run 24/7 blowing air out that wouldn’t matter but if they cycle on I would imagine during the phase they are off would cause a moisture gradient in which the RH in the crawlspace would spike. Are they energy intensive or have a low energy consumption profile?

    • Michael Church on August 12, 2021 at 10:31 am

      The EPA recommends running the fan 24/7. I am sure they do affect humidity some but the power of our dehumidifiers takes care pf that. The Aprilaire E Series dehumidifiers and our foundation vent fans are some of the lowest energy users on the market. I believe the fan uses around 1/2 an amp and the dehumidifier varies by model. Hope that helps. Thanks.

  7. Mike Mantino on August 25, 2021 at 5:19 am

    How is the air made up if a vent fan is taking it out? The space being ‘sealed’ and encapsulated suggests that there is no way for air to get into the spade, but the vent fan will be taking air out. Where is the new air coming from? Are you relying on leakage from penetrations? Or is air brought in from the home through the a/c ducts?

    • Michael Church on August 30, 2021 at 1:12 pm

      Great question Mike, most crawl spaces have leaks around the perimeter or living space for the make-up air to enter. We are only using 1 cfm per 50 sq feet calculation so it is not difficult for the crawl space to have leaks to provide that low of air flow. Hope that helps. Thanks.

  8. Craig Bowman on August 25, 2021 at 4:36 pm

    Hi Michael. I live in Western North Carolina and I have a small 8′ X 24′ (192 SF) crawl space under my utility room. It is slightly damp on one side (with a ton of crickets!) and causes the utility room to smell bad all the time. I am in the process of encapsulating it now. It has 3 foundation vents to the outside. I am assuming I will still need to vent the space regardless of the size? I had originally thought I would have to plug off 2 of the vents and install a vent fan in the 3rd vent, but then wondered where will the air come in from for the fan to exhaust the space? A dehumidifier would be way overkill for a space that small, wouldn’t it? I’m not even sure how I would put one down there (or if they even make one that small). There’s not much room between the crushed stone ground cover and the floor joists. There is very little if any mold down there now, so I don’t want to create an atmosphere for any to start growing. Thank you for all of your videos and taking the time to answer questions.

    • Michael Church on August 30, 2021 at 1:20 pm

      Hi Craig, thanks for watching our videos and reading our articles. Small crawl spaces with little room for dehumidifiers may still require ducted dry air into the space from another part of the home. This could be done from the living space but the severity of your crawl space issue and the expense to do that would be for you to decide. If you don’t notice mold I would still test humidity and wood moisture levels to ensure the wood is dry. I assume in West NC your outside is humid like ours so fans alone will most likely only draw in more humid air. Normally there are enough air leaks around the perimeter of the foundation for the make-up air. This is why a dehumidifier would be needed if you decide to ventilate to dry that make-up air entering the crawl space. There is a chance even more humid air will enter the space if fans are installed and no dehumidifier which could make the problem worse.

  9. Amanda on September 12, 2021 at 8:41 am

    Hi Michael,

    I have a fully encapsulated crawl space. The installers put a vent grill from my HVAC right into the crawl space. The humidity is too high. Should I close that vent OFF and add a dehumidifier and exhaust fan?? OR do I leave that HVAC conditioned air and add a dehumidifier and exhaust fan?


    • Michael Church on September 13, 2021 at 10:51 am

      Hi Amanda, every home is different but we don’t usually recommend HVAC to control crawl space humidity. Dehumidifier plus foundation vent fan is recommended. Here is a video that I hope helps. Thank you. https://youtu.be/e6bE6YGOxnU

  10. David Thibodeau on September 24, 2021 at 2:11 pm

    Hi Ninjas!

    Ok so I’ve getting great info (via your You Tubes) about encapsulated crawl spaces and ventilation.

    However I still have not found any clips addressing my particular concern about ventilation. I get that the EPA requires an exhaust vent even with a closed crawl space because of potential build up of soil gasses.
    But if the area is encapsulated then would there be any threat of soil gasses?

    • Michael Church on September 25, 2021 at 2:36 pm

      Hi David, for us a closed and encapsulated crawl space are the same thing so yes, if you close the vents, regardless of how you install the plastic, the EPA recommends a vent fan to address soil gases. Hope that helps. If I misunderstood your question, please let me know.

  11. Fred on October 30, 2021 at 9:44 am


    I have a fully encapsulated 1300 sf crawlspace which is conditioned by dampers in the ductwork. My issue is not humidity it’s odors probably caused by off-gassing from the plastic and foam. The odor is present in the living space when the house is closed up (such as returning from vacation) or now, when the gas heater is running. I live in Chapel Hill, NC and we have not had issues with pipes freezing but since the odor is more intense when the heater is on, I’m concerned that fans that shut-off at 40 degrees might not work as well. Before we encapsulated we put in a new foundation drain and sump pump system and it made the house much more comfortable. Your feedback would be appreciated. Thanks.

    • Michael Church on November 8, 2021 at 12:13 pm

      Hi Fred, we just did a video of addressing crawl space odors under the plastic and also mention addressing odors over plastic. Hope it helps. Thank you. https://youtu.be/QNPVXrDcFWk

  12. Dan on December 13, 2021 at 4:50 pm

    Can you post the link to the EPA documentation with verbiage that recommends it please. Everything I read on the EPA’s site is in regards to radon with the verbiage you posted above, nothing about requiring it when encapsulating the crawlspace.

    • Michael Church on December 14, 2021 at 2:57 pm
      • Dan on December 27, 2021 at 1:10 pm

        Thank you!

      • Matt on December 30, 2021 at 9:12 pm

        Hi Michael,
        I have one of your systems in North Alabama. I’ve been surprised by how much the dehumidifier runs. I’ve search high and low for cause, but I believe it’s partially due to exhaust fan CFM.
        I agree with all your statements above.
        However, I searched latest IRC2021 code. In section R408.3.2 it states ONE of the below items is required (abbreviated):
        R408.3.2.1 Exhaust fan (this topic)…
        R408.3.2.2 Conditioned air supply…
        R408.3.2.3 Plenum…
        R408.3.2.4 Dehumidifier (exist)…

        Due to dehumidifier in place, it technically meets criteria. I don’t have access to all code, so not clear if this option is new.
        There’s code, then there’s best practice…
        I think I will be exploring automated exhaust to prevent pulling air at high humidity times.

        Also to note, R408.3.2.1 says when exhausting crawlspace, makeup air should be pulled from “pathway to common area”. This is illustrated in your reference document well. I don’t think this is talked about much.

        Anyway, thanks for all of your education and content.

  13. Jess on February 24, 2022 at 10:25 am


    I live in Richmond VA and have been having odor issues since day 1 of encapsulation. We DO have radon system, two small exhaust fans, and a Santa Fe 70 pint for my 1200 ft crawl.

    Is bringing in air from outside a good idea in Richmond? Some contractors are saying we need a “cross breeze”( cross ventilation) but that seems like it would just be bringing in humidity causing mold.

    If a radon system under the poly, exhaust fans AND a dehumidifier are not controlling the odor , what else could it be?

    • Michael Church on March 5, 2022 at 10:20 am

      Sometimes the odors could be coming from decaying materials under the vapor barrier, mold present on the wood that was not properly removed or remediated, the vapor barrier itself or multi-layers of vapor barrier. All of which, adding more ventilation will probably not help. You may want to get a reputable professional with mold removal experience and crawl space experience to assess the situation. They will need to pull back sections of plastic to determine if there are problems under the vapor barrier. Keep in mind, that could void warranty of radon system. Hope that helps.

      • Jess on March 8, 2022 at 8:34 am

        I appreciate the response! When we installed our exhaust fans we were told to drill a 3 inch hole in our first floor living area (and put a little metal grill) so the exhaust fan could pull air from the living space creating a neg. air pressure. Do you think since we have our exhaust fan pulling from the crawl AND the first floor living that we should seal up the two little holes in our floor so it ONLY pulls from the crawl?


        • Michael Church on March 8, 2022 at 1:08 pm

          I am not a fan of having holes in my floors to crawl spaces from a pest perspective alone and I don’t see it as much of a benefit for moving air out of crawl space. The other thing is your HVAC fan is more powerful and may reverse air flow into your home from the crawl space. Windows open can do that too. Hope that helps.

  14. Jess on March 10, 2022 at 10:10 am

    Thanks for getting back to me. I appreciate it!

  15. Randy on April 25, 2022 at 10:01 am

    Hey! I live in Ottawa, Canada and there is a very potent smell coming from our crawlspace aswell as a whole bunch of condensation down there, we are going to encapsulate our crawlspace and install a dehumidifier. Now we have open vents with a grill one in the front and back and were wondering if it would be a good idea to install a vent fan pushing the air outside with a dehumidistat at the front of the house for radon concerns and keeping the back vent open? What are your thoughts on this?
    Thank you!

    • Michael Church on May 2, 2022 at 9:41 am

      Hi Randy, Installing a dehumidifier with a foundation vent fan is a great idea according to the EPA that recommends 1 CFM of air movement out of crawl space for every 50 square feet to address soil gases. We had a local codes enforcement that asked us to leave a vent open at the opposite end of the vent fan so air could be drawn in to assist with ventilation. They abandoned that requirement when they realized homes have make-up air for entry around sill plate and foundation wall and other areas. I think the open vent with fan is unnecessary unless your crawl space is extremely air tight and does not allow any make up air to enter from other areas. Hope that helps.

  16. Patti on May 10, 2022 at 2:11 am

    Hi, I live in Ontario, Canada…we had our crawlspace enscapulated in 2019…we also had the Aprilaire Dehumidifier installed…and the cs vents are completely blocked…so we have absolutely no ventilation…
    In the summertime the house gets very hot and humid, so I have to keep a small window open slightly all the time, I even have to keep that window open in the winter or our roof gets full of ice because of a lack of ventilation from below…plus since the enscapulation I have noticed the floors squeak more..My question is can I open the CS vents in the spring/summer?..I really don’t know what to do at this point..I’m very confused about this whole enscapulation thing…Thank You…

  17. Frank Ongaro on May 24, 2022 at 7:34 am

    Hi, I have an encapsulated crawl space and until recently I had a dehumidifier in there. The dehumidifier didn’t appear to run very often in the past and lately I found out it died. When my crawl space was encapsulated they put in a device that pumps some conditioned air from the main floor into the crawl space. That unit sill works. My question is – do I need a dehumidifier since it is getting some conditioned air from the main floor? Could I just install a crawl space vent fan with a humidity sensor to pull out some stale air? Also, just to let you know, the crawl space currently has no venting. All of the vents were sealed off when encapsulated.


    Frank from Tennessee

    • Michael Church on May 25, 2022 at 9:33 am

      Hi Frank, we get that question a lot. I am thinking you will need a dehumidifier but you can install a humidity reader and the fan and see if that takes care of it with your current venting setup. I would install a humidity reader you can see from your leaving space and monitor it daily when seasons in your area change. Summer will be the biggest test most likely. here is one you can install https://diy.crawlspaceninja.com/thermopro-tp65/. If you find humidity at 60% or higher, investing in a dehumidifier like the Aprilaire E Series is my recommendation. Here is a link there: https://diy.crawlspaceninja.com/dehumidifiers/

  18. Jason on August 7, 2022 at 10:03 am

    Hi Michael, can you recommend anyone in the Los Angeles area? I joked with my wife that I wish I could fly you out here. Thanks so much.

    • Michael Church on August 8, 2022 at 11:02 am

      Hi Jason, I am extremely flattered you’d say that but unfortunately I do not know of anyone in the Los Angeles area.

  19. Anthony on August 11, 2022 at 10:24 am

    I’m in Denver metro. Should my crawl space vent fan blow air into the crawl space from the outside or blow the air outside from the crawl space.

    • Michael Church on August 11, 2022 at 11:42 am

      Hi Anthony, it shouldn’t matter either way because blowing air out will pull air in from outside, blowing air in should push air to outside. That being said, I’d blow air out if given the choice during installation. But we are using fans to assist with soil gasses versus humidity control. You being in Denver may not need a dehumidifier since outdoor humidity is low on average. Hope that helps, thank you.

  20. Kelly Coy on September 24, 2022 at 9:32 am

    Hello sir,

    We are building in Saluda, NC and we’re in the framing stage and we have a lot of moisture in the crawlspace already. We chose to have an un-vented poured crawlspace with access from the interior. So, no outside access. As soon as it’s dried in we want to move forward with encapsulating it. Who would you recommend in our area?

    Mr. Kelly Coy

    • Michael Church on September 27, 2022 at 2:12 pm

      Hi Mr. Coy, I appreciate you reaching out to us. I don’t have a referral for you but I asked our Ninjas to reach out to you and see if any of our current locations can assist you. Also here is a link to our current service area. Thank you. https://crawlspaceninja.com/service-area/

  21. Adam Bowman on November 10, 2022 at 10:19 am

    I had my crawlspace encapsulated professionally but the installers didn’t install an exhaust fan. Will adding an exhaust fan create a negative pressure in a sealed crawlspace and draw in radon?

    • Michael Church on November 22, 2022 at 5:56 pm

      Hi Adam, radon can enter with or without ventilation. Your home is naturally ventilating due to the stack effect. What a radon mitigation or foundation vent fan may do is direct the air outside before it can enter the living space. Hope that helps!

  22. Murray Banting on November 17, 2022 at 12:10 pm

    Hi, here’s what I have. It’s an encapsulated crawl on a slab. Has a few passive vents for some air movement. There doesn’t seem to be a moisture issue but being a renovation there is the old musty smell of the old wood etc. It seems to get into the home some. I’m thinking of adding a basic bathroom type ventilation fan ducted to outside. I was going to put it on a timer to run maybe an hour a day in winter and maybe alter to 2 hours in summer. I just want to circ the air to help remove stagnant air. Climate is pacific NW. Hot and dry summer cool and damp winter but not too many freezing days . Crawl is about 1400 ft 2. X 24”. What do you think of this idea. I have a small heater in there too if it gets to cool will run. I don’t think it runs often. I also thought maybe just a fan running again on a timer to simply circ the air in the space and leave the small passive vents open all year round. There’s only 3 at 4” dia dryer type vent openings with bug screen. Any comments are welcome. I read your articles but didn’t see much about mechanical venting or like I was planning on a controlled basis.

    • Michael Church on November 23, 2022 at 4:53 pm

      HI Murray, I appreciate you reading our articles. Humidity is tough to see and wet wood is also hard to see or determine without humidity and moisture meters. Many homeowners have told me their crawl space is not wet because they don’t “see” water but meters can give an accurate assessment. So I’d recommend getting at least a long term humidity reader that sends alerts of high humidity. Here is an example Govee Humidity Reader. After the humidity reader is set and measuring moisture levels, then you can adjust fan run times to see what works best. Sounds like there is a better chance during winter to bring in moist air from the outside versus summer, which is the opposite of our situation. Hope that helps. Thank you!

  23. Chris on January 22, 2023 at 9:29 am

    Hello Michael,
    I have a crawl space -1700 sq ft. It has had high humidity issues for years and I started trying to address with ventilation, spray foam under subfloor, etc. I live in south east Oklahoma so eventually realized you can’t fix humidity in a crawl space by venting in air in a high humidity climate.
    I found your forums and decided to go the encapsulation route, in stages.
    1. installed Alorair Sentinal HD90 dehumidifier
    2. Closed foundation vents

    Humidity has improved, typically in 50’s vs 70s. I will probably still install vapor barrier, but due to the amount of labor (very rocky in crawl space) feel this is less urgent than before.

    1. if I already have a large exhaust fan 1200 CFM installed in crawl space door, do you think it’s sufficient to have that run at some interval, i.e. a couple times a day for 5 minutes or instead of adding a small vent fan?
    2. If the dehumidifier is maintaining the humidity level in the 50s, is it still necessary to install vapor barrier for other reasons?

    • Michael Church on January 23, 2023 at 12:59 pm

      Sounds like what you have done is working. Installing new properly encapsulated vapor barrier could help the dehumidifier run less. Also building code says a loose laid vapor barrier is obsolete once the vents are sealed. In other words, if we were working for you, we’d upgrade your vapor barrier but if your crawl space humidity is staying low as is, that’s great. You may get dinged on a home inspection report if they know the code. Also the 1200cfm fan probably uses way more energy than a 1/2 amp 110 cfm fan like the Lomanco PCV1 but again it is working. The guideline is designed for 24/7 365 use, so if you kept that big fan running like that it will eat up power. Hope that helps.

      • Chris on January 23, 2023 at 9:44 pm

        Thanks for the response!
        My thoughts on the 1200cfm fan would be to run it briefly multiple times a day to clear out any gases.

        I don’t currently have a vapor barrier. Is it a requirement if humidity is mangeable without?

        • Michael Church on January 24, 2023 at 4:31 pm

          Your welcome. I would recommend a vapor barrier to help control humidity.

  24. Doug on May 28, 2023 at 4:48 pm

    I’m in NC. I had my 45 year old house’s crawl space encapsulated. After a while i started having a musty smell in the house. It was obviously coming from the decades of having an open crawl space. I had a ventilation fan installed. It seemed to help a little, as you can smell the musty air being blown out when standing near the fan outside of the house. I still have the issue on the inside though. My question is, should I unseal a vent or two to have fresh air circulated in the crawl space? There is a dehumidifier in there because I live in very humid eastern North Carolina. I just want to stop the musty smell from coming into the living space.

    • Michael Church on June 10, 2023 at 3:49 pm

      I would recommend you ensure there is no mold present. If there is, have it addressed and that may take care of the musty smell. Also, porous materials trapped under plastic can grow mold too. Please ensure there is no wood or mold growing materials under the plastic. Hope that helps.

  25. Chuck on June 13, 2023 at 4:01 pm

    We recently had our crawl space encapsulated with a dehumidifier and vent fan. The vent fan is taking in air from between the soil and encapsulation and pushing it out from the normal house vent … all other vents for the house have been sealed. Should the vent fan be above the encapsulation material or between it and the soil?

    • Michael Church on June 14, 2023 at 2:42 pm

      What you are describing is used more for radon mitigation. So there is a possibility you need both. Above the vapor barrier as we install in all crawl spaces and between the plastic and the soil if you have radon. Hope that helps.

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