var root = Model.Content.AncestorOrSelf("[YourHomeNodeDocumentType]");
I'm not sure if this is Umbraco 6 syntax, but what you want is that AncestorOrSelf traveersing call. I have many multi-site-multi-lingual setups and I use that all the time. The "or self" portion is fun, in some cases that "root" node is a page.