Insulating crawl space in older home
Where do you live and what kind of heat?
If you have forced air heat, you might consider a conditioned crawl space: line the floor with plastic, line the foundation with insulation and add a register or 2 in the crawl.
Results can vary for location
See also http://www.buildingscience.com/
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10 …. I have laid the foundation like an expert builder. Now others are building on it. But whoever is building on this foundation must be very careful.
11 For no one can lay any other foundation than the one we already have–Jesus Christ.
1 Corinthians 3:10-11