My mum wont let me keep my guinea pig inside what should i do?

Hi i have 3 guinea pigs currently living outdoor under a shelter but i feel that they are cold at night as we are in winter. I would love for them to be in my room but my mum just wont let me what should i do. At night i put 2 blankets over the hutch but i would like for them to stay in the garage (never been used) is it ok to put them in the garage or do they need direct sunlight please help as this is my first time having guinea pigs.