I have a 7 year old lab mix male who is a house dog. He never pees in the house. We have a kennel room where we put him and our other dog (6 year old lab female) at night and during the day when we are gone. He never used to pee in there but over the last few weeks has been peeing every night. He doesn't pee during the day though. He goes outside for about 1/2 - 1 hour before being put in the kennel. Water is also limited before they go into the kennel. The vet couldn't find anything wrong either. Help!

I personally am a fan of crating overnight to, but have you considered leaving him in a room instead of the crate?
I bought a baby gate to block my dogs off in one part of the house when I go out.

Does he have a problem with being in the crate? (crying, shaking etc)

He's not in a crate. It is just a room on our lower level. We haven't had any problems until recently and he is only doing it overnight. He doesn't cry, shake or show any signs of not wanting to go in there.

Ahh OK, you might want to consider crating then.
If crates don't work then I let them free run in a room, but if a room doesn't work I use a crate. It just depends on the individual dog as to what works.

Dogs will rarely potty in their crate as they know it is their bed and their 'safe spot'. Whereas if they have a whole room to roam around in then they use one part as their bed, and the rest of the room is just space.

If you do want to try this I can give you some tips on crate training, or if you would rather leave them in the room downstairs then I will rethink.