Editing Foundation with Sass (section)

=== Foundation 5 ===

Foundation 5 offers a collection of Sass files that they suggest customizing. <ref>[http://foundation.zurb.com/sites/docs/v/5.5.3/using-sass.html How to Use Foundation Sass] Foundation documentation (version 5)</ref>

* Variables controlling appearance are located in `_settings.scss`
* The documentation recommends placing custom styles in `app.scss`
* Foundation components can be included or excluded by commenting them out in `app.scss`

Question: how well does this arrangement accommodate upgrades? Do these two files get overwritten in the course of an upgrade? How to preserve changes?