a hidden ventilating sill plate is fundamentally a new building product , installed along the top surface of the exterior perimeter foundation . it replaces the existing wood sill plate . the invention has a continuous set of air slot channels of a proscribed size perpendicular to the longitudinal axis , along its base , communicating natural air flow from the exterior to the interior of the crawlspace . the exterior side of the slot channels can open earthwards to allow the venting to be completely hidden from view , when the sill member extends out beyond the exterior face of the foundation and wall . the vent concealment feature also functions as a base to the siding and an integral drip edge . insect mitigation is achieve by adding a mesh screen over the exterior exposed slotted openings . the preferred material for this invention is a plastic - fiber composite , allowing rot resistance , shear capabilities and , rapid extrusion or molding of the sill profile .