If you are wondering why your teenage son is spending too much time in his room then I think I can help you. For quite a long time, my son would come in from school and just go straight to his room only coming out for food. It scared me and I wondered what he was up to in there. I helped him and he thanks me to this day. Here are some tips for those wondering about teenage son spending too much time in room.
He's socially shy - It is very possible that your teenage son is shy socially and even maybe around his family. He might feel embarrassed about a certain part of his body or just be too mentally confused with his life. This happens to nearly all teenagers at some stage and is kind of natural. They are going from childhood to becoming an adult and so their bodies and mental state and social circles change rapidly. This can be stressful.
The best thing you can do is show them unconditional love and try to bring them out of their shell a little bit. Give them a feeling of responsibility around the house and tell them that what they do is very important to keeping the house in balance. This will make them feel special and I promise you will be surprised at the results.
Give them independence - your teenage son might be spending too much time in his room because he feels that he is overwhelmed by all the laws of the house which he feels that he does not want to follow. Give him a feeling of independence that he wants and he will come out for sure.
If you give his $10/week for example for doing chores, you could say you can pick how much you get up to $15 and he will do a better job. Also a good idea is to let him pick rewards that he personally wants to work towards.