Best Practices Manual

8.1 Crawlspaces: General Guidelines


1. New Construction: Conditioned Crawlspace with Insulated Slab (8.2)

  • Treating the crawlspace like a mini-basement with an insulated wall and slab is the highest performance crawlspace option.

2. Retrofit: Conditioned Crawlspace with Soil-Barrier (8.3)

  • This is the best retrofit option in crawlspaces that contain mechanicals or ductwork, or are interconnected with a conditioned basement.
  • Install a Sealed Seam heavy duty (12 mil) soil barrier to seal the space from water vapor and soil gasses.

3. Retrofit: Vented Crawlspace with Floor Encapsulation (8.4)

  • Acceptable option for crawlspaces without mechanicals or ductwork.
  • Install new plastic soil barrier with lapped seams. Heavy duty soil barrier with sealed seams optional.
  • Air space should be maintained between floor and spray foam if underfloor hydronic tubing is being used for radiant heat.
Crawlspaces General Information Detail | Hammer & Hand

To Know Before Building or Retrofitting a Crawlspace:

  • Moisture management: all surface and ground water must be properly managed prior to sealing and insulating a crawlspace.
  • DO NOT route ductwork through unconditioned attics or crawlspaces. All water supply lines must be insulated even in a conditioned crawlspace.
  • Cleanup: crawl must be thoroughly cleaned of all dust and debris after construction is complete and any damage to the soil barrier must be repaired.


Continue to 8.2 New Construction: Conditioned Crawlspace with Insulated Slab >>>

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