I have an older home built in the 30’s which I completely renovated and out an additional on.
I always had a problem with ice build up in the roof valley where the new addition met the old (not properly ventilation) roof. Warmly Yours finally made a heating cable that could be used on steel roofs. So far I’m coming up on the 3rd winter and it solved my problem! I just run a single cable up one valley and over the peak on down the back valley and it clears the way for the melting snow to leave without turning to ice buildup. Only problem I had was a few of the glue pads let go the first year and I had to get up and replace them. It was fairly expensive but it works better than anything I’ve tried before and I’m happy with the results and customer service.