A. Bruce Nelson responds: We have found that many different materials can work, but that some require more expensive installation than others to give equal performance. There’s still much we don’t know, but our investigation of 59 foundations in Minnesota and discussions with others in the field suggest the following:

Also, foam plastic is not your only option. Consider high-density fiberglass board for sites where foundation-wall drainage is a must. This material is available as a commercial roof insulation from Owens Corning. It is only available for residential use in Canada, as BaseClad (Fiberglas Canada, 4100 Yonge St., Suite 600, Willowdale, ONT, Canada...

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