Heating a room without a "heater"

If you don't care about the situation move to the last paragraph.

I'm an 18 year old full time college student living at home. I work a part time job where I get paid in cash, on top of some jobs I take on, and average probably around 500 bucks a month (give or take depending on how much I hustle). I'm a pretty private, independent person, and I NEED my own space. My room is unfinished about the size of a utility closet with no furniture, I just got a bed that fits me this year (I'm 6'6'' and was sleeping on a twin mattress on the ground). Not to mention right across the hallway is my sisters room, and my other sisters room (who lives away at college), completely finished looking like a hotel suite. Not to mention people constantly enter my room for things and I don't have a lock. There's literally not enough space for a computer and a desk. I've never had the opportunity to design and furnish my own room like the other people in my family. Basically, my family is loud as all hell, invasive, and doesn't know boundaries, so I started moving into my garage. I could really go on about this all day how I'm being shafted.

Now trust me, my first solution is moving out, but I really am incapable at the moment with my school schedule interfering with work, as well as having to pay for literally everything (car, food, clothes, insurance, amenities). This is really my only option at the moment. I recently purchased all of my own stuff with money I'd saved over the years. I mean like, a desk, chairs, a computer, a tv, so I would get screwed over less by my family while I have to stay here, as well as have a quiet place to work. I moved into my garage which isn't primarily used much and I've been working on insulation and organization for months. It took me weeks to completely clean out and optimize this large space for my presence.

Basically, I'm pretty limited with what I can do here, and I need to heat the garage. I'm in New York, so there will be cold winters. The garage is being pretty well insulated, and it's a large room so I plan on literally partitioning a section off so it's easy to maintain heat where it counts. But insulation is nothing without a heat source, and here's the kicker; I'm not allowed to get a space heater. I was planning on getting the top rated safety and efficiency space heater for about $130.00, but that is out of the question because my father is too worried about a fire hazard, and honestly reclaiming power over my space. Get this; the garage is even connected by the central heating system, with no thermostat (so it would heat in accordance to another room's temperature, which would only bring up the heating bill by a minuscule amount). But my father refuses to heat it (even though I would pay the increase in the heating bill).

Basically I need a way to heat a small space WITHOUT a space heater, and please, no open flames heheh. It just needs to be livable and functional. As long as I can keep that space above 50-55 degrees I'm happy. I'd love to just get a space heater and hide it, but being caught would likely result in me being kicked out, which might end up being my last resort.

Thanks guys, any help is much appreciated.