Husband wants to live alone

My husband is a gentle man who needs a ton of time alone. He has his own room where he pretty much hangs out all the time and even sleeps. I’ve gotten used to this though I do admit to wanting more physical/emotional closeness with him. I’ve learned I cannot “demand” that closeness. Now he is proposing living separately but still staying married. He is not interested in seeing other women, so that’s not it. I know I will continue to love him no matter what, but living apart while married is not acceptable to me and I am struggling knowing that that is what he wants. Can you please comment. Thank you.