Where to install tankless hot water heater
Having weighed various pros and cons, I am leaning toward replacing my tanked water heater with a gas tankless if it is feasible.
We would have a professional installation, but I am trying to get an idea of site-ing issues and potential retrofit costs.
We have a townhouse, on a small lot. Our current tanked water heater is in a room at the back of our house (brick walls). The brick backs up to a wooden shed at the back of our property line. The shed is a sturdy structure with a roof. Our current water heater is vented through the chimney flue. We can't vent a new tankless system through the side wall of the "water heater room" because of the location of our neighbor's house.
I was wondering if any of the following would be possible:
1). Mount on interior of back brick wall. Water heater would "direct vent" into the shed. If this is allowable, how much clearance is needed from vent to roof of shed, from side walls of shed, etc.
2). Mount on exterior of back brick wall, inside of the shed. This is assuming that venting in the shed is not an issue (from #1).
3). Mount on exterior side wall of house. (the side wall opposite the one where the current "water heater room" is). This location would be near the gas and water meters.
An additional concern I have with #2 and #3 is pipe freezing. I have heard that exterior machines have mechanisms to prevent freezing ... but what if the power goes out? I am in Virginia near Washington, DC.
Thanks in advance for your thoughts!