What are the guidelines of tznuit inside of the home?
The rules for tznius in the home summed up in Shulchan Aruch O:C 2:2, “One should not say to himself I am in the privacy of my own home, no one sees me, for Hashem’s glory fills the world”. So one must conduct himself with modesty even in the confines of his home. Igros Moshe [Y:D 3:47] writes that it is clear from Chazal that covering one’s self at home is a matter Midas Chassidus and שויתי ה לנגדי מתיד, and not an absolute halacha. For this reason it seems, the Rambam doesn’t bring it at all. The basic guideline Rav Moshe zt”l writes is that one need not dress as he would in the streets and when out meeting people. Rather it is sufficient to be dressed in a way he would not be embarrassed if someone were to visit him in his home. And even then not a special honored guest, but the average guest he does not specifically need to honor, but to be respectful in front of them. It would seem this criteria is relative and may change from one person to another.