Why Does Crawl Space Humidity Spike After Encapsulation

Why Does Humidity Spike After Encapsulation? Before I can answer that I need to let you know what we consider crawls pace encapsulation. For the purpose of this article we are saying the crawl space has vapor barrier installed on walls, floor and pillars. The plastic is overlapped and taped. The vents are insulated and air sealed and a dehumidifier is installed.

Wet Wood Raises Humidity

As the dehumidifier dries out the crawl space, keep in mind the wood may be wet. Different types of wood hold more or less moisture than others. When we inspect a crawls pace we always check the wood moisture level. Even if visible mold is not present, high wood moisture levels can support microscopic mold growth. Microscopic mold or wood rot fungus will eventually become visible if the wood moisture level is high. As the dehumidifier dries out the wood, the humidity spikes.

Encapsulation After Picture

Humidity Spike from Ground Water

Many homeowners assure us their crawl space has never flooded but it is a good idea to check for signs of moisture during the inspection. If you encapsulate the crawl space and standing water happens after heavy rains, this can cause humidity spikes. Signs of past flooding include muddy vapor barrier, efflorescence on cinder blocks, concrete, stone and bricks. Other signs of flooding is plastic that has shifted away from the foundation wall.

Mold Remediation in Crawl Space

Many companies use liquid mold cleaners to address crawl space mold problems. The crawl space should always be dried before mold remediation. If the crawl space is dry and chemicals are applied, this can also create a humidity spike in the crawl space.

Do you need crawl space encapsulation? If so, please contact Crawl Space Ninja and we will be glad to help. Also, let us know in the comments below if you have noticed other foundation issues we did not mention in this article.

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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. James on November 4, 2020 at 1:06 pm

    Do you encapsulate then dry and remove mold or dry, remove mold then encapsulate?

    • Michael Church on November 18, 2020 at 12:33 pm

      You should always dry first. Here is a video that may help “Crawl Space Mold Removal – What NOT To Do! Crawl Space Mold Treatment | Crawl Space Mold Mistakes” https://youtu.be/DdknHGFEKH8. Thank you.

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