Insulating Exterior Basement Walls of Older Homes

[Linda Guthrie]

I've been researching residential energy savings projects for a community-wide energy initiative in a town where 70% of residential buildings are older homes. My initiative will use the Amish "barn-raising" method of gathering the expertise needed, training neighbors and going out to perform the project, paying itself forward with new trainees from each house we agree to work on. Similar community initiatives exist to install solar thermal hot water heaters, but i believe energy efficiency trumps all other measures as a starting point. i have chosen insulating exterior basement walls. My research yields incomplete or little information on the primary foundation type for our dominant older New England residences -- stones and mortar, usually crumbling in places. I'm wondering if all crumbling mortar has to be replaced/repaired first. Even though this is an exterior project, what if the interior basement mortar is even more crumbly all over (typical)? I think it's unrealistic to be able to locate ALL leaks individually so what about overall exterior water proofing first? Given the guaranteed uneveness of these old exterior basement walls, is furring necessary? If so, would metal strips be better than wood since dampness is a given (long standing snow). What is the best way to combat the waviness that will result from the uneven exterior surfaces?
I figure we'll have to use rigid foam & that above grade walls will need metal or stucco surfacing. Thanks for your input!

[ArmchairDIY]

Although this is not a direct set in stone answer to your question, it may still prove useful I hope.
Retrofitting existing stone foundations with insulation and waterproofing can be difficult. One solution I have considered, but have not tested yet may be a possibility.
Search for "frost protected shallow foundations" This system was designed for slab on grade type construction, but I believe the principle behind it could prove very useful and cost effective for basement retrofit situations.

Basically you insulate the exposed portion of the basement wall, then extend insulation out perpendicular to the wall around the perimeter to prevent frost penetration. The perimeter insulation would also act as a water diversion to move roof run off away from the foundation if positioned correctly.

Again, this is only a theory on my part, but it may be a very real possibility for you.

[GBR in WA]

I believe the mortar needs repairing first as it would let water inside. Drain tile outside, sloped or pumped to a dry well or acceptable sewer. Gravel under and around to prevent frost heaving. Insulation as Armchair said, which I encourage since I researched it a year ago, mainly for deck footings against frost jacking. A waterproofing spray or brush on sealer outside with/out fabric. Building a deck: expert advice from ... - Google Books
How Aggregates Prevent Frost Heave

ESB: Frost-Protected Shallow Foundations
http://www.waltersforensic.com/artic.../vol1-no11.htm
Foundation Drainage
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Be safe, Gary