About 4 years ago there was an issue down the street with the main water line and the water was shut off on the whole block. When the issue was corrected, the water was turned back on. But, we lost our strong/normal hot water pressure on the second floor of our home. It was as though something came dislodged in the line and clogged it up. The first floor of the house is completely fine - hot water with normal pressure. We have dealt with the low pressure for years now. However, in the past couple of months we are now having trouble with water temperature. So, we not only have low pressure but also just semi-warm water. I know part of the issue is fighting the extreme cold outside temps we're dealing with. But there is still an obvious problem somewhere.

I should add that the shower has a single handle. The sink, with the same problem, has dual handles. The hot water heater is in the basement, wrapped with installation and turned up to "high". I have also purchased a new shower head and this didn't help either.

Do we need a new hot water heater? New pipes run? Where should I begin searching for my problem(s)? Any ideas on how to solve our problems?

Thanks in advance.

Clean all aerators on the faucets, shower heads and pull the cartridge on the single handle mixer. Clean out all orifices. Input water temp will affect the heater, particularly with the cold weather. You may also have a dip tube issue. If the dip tube is broken, you will short circuit water rather than heating it up.

I agree. Pull cartridge of shower valve, turn on the hot water briefly to flush valve. Same for lavatory, remove hot water stem and flush valve. Doesn't sound like water heater dip tube to me, unless other baths have same problem.