Closed Crawlspace Air Sealing

Verify that all exterior bulk moisture is directed away from the foundation with appropriate drainage techniques and exterior foundation drainage details are functioning properly (e.g. rain screens, weep holes)

Select sealants that:

are compatible with their intended surfaces,

allow for differential expansion and contraction between dissimilar materials,

meet the requirements of the applicable fire safety code (e.g. thermal or ignition barriers), and

for use inside the pressure boundary select low volatile organic compound (VOC) sealants that meet independent testing and verification protocols

Select materials that:

adequately support applied load and are permanent air barriers,

meet the requirements of the applicable fire safety code (e.g. thermal or ignition barriers),

for use inside the pressure boundary select low volatile organic compound (VOC) materials that meet independent testing and verification protocols, and

pest-resistant materials that are rated for ground contact anywhere they are in contact with the exterior foundation walls, piers, or bare earth

Install steel wool or other pest-proof material as infill in gaps greater than 1/4" before sealing

Install support material for spans wider than 24", except when air barrier material is rated to span greater distance under load (e.g., wind, insulation)

Remove any material from the sealing area that will prevent full adhesion of the selected sealant

Permanently close vent openings using a durable, rigid, and pest resistant material

Apply a continuous seal at all seams, cracks, joints, penetrations, and connections of foundation walls, sills, floors, etc. that are adjacent to unconditioned spaces while applying sufficient pressure to push sealant into any gaps or cracks and contact any backing or infill material required

Weatherstrip exterior access doors/hatches and seal door/hatch framing using compatible sealant

Install a continuous air barrier and vapor barrier between adjacent unconditioned spaces and closed crawlspace

Install only noncombustible materials and sealants in contact with any device producing 200 degrees F or more (chimneys, vents, flues, etc.)

Foam plastics, where permissible, will be provided with ignition and thermal barriers as required by applicable fire safety code