Basement & Crawl Space Insulation in Oshkosh, WI

Basement and crawl space insulation around Oshkosh has to start with water. The Wisconsin Geological and Natural History Survey describes much of Winnebago County as covered with red, clay-rich glacial lake sediment and clay-rich till that it calls relatively impermeable to stormwater. Water that cannot soak in collects against foundations, and many basements here stay damp or seep in spring. Insulating over that hides the problem and can trap moisture in the wall.

Moisture first

During the visit we look for seepage lines, efflorescence, cracks and musty smells, and check where gutters and grading send water. If there is active water, we tell you and recommend fixing it before insulation. Once the wall is dry, closed-cell foam is the right material, because it does not absorb water and keeps humid basement air off the cold concrete.

Rim joists

The rim joist, the band of lumber that sits on the foundation, is the leakiest part of most basements. Closed-cell foam seals the sill, the joist ends and every pipe and wire hole at once. HomeGuide rates it at R-5 to R-7 per inch.

Walls and crawl spaces

The Wisconsin code summary lists R-19 cavity or R-15 continuous for basement walls in Zone 6. For finished basements we foam or board the walls before framing. Crawl spaces under additions and porches get foam on the walls, a vapor barrier over the soil and sealed vents, so cold, damp air stops reaching the floor above.