as mentioned by other members, i HIGHLY recommend crate training. it may take quite a while but ur pup will get used to it. he is only 4.5 months old so now is sthe perfect time to teach him that howling does not mean that you will come and take him out and that a crate is a good place to be in.
did you try giving him his meals in the crate with the door closed? that may generate positive associations... but at 4.5 months dont give up, yes the pup may throw hissy fits, but you need to be patient and more stubborn that he is.
Monkey and Amy (cats)
“Dogs believe they are human. Cats believe they are God.”
"The average dog is a nicer person than the average person."