Electric water heater location

[chuck b]

re: Small Seasonal Cottage - Northern Michigan Lake

The bathroom is very small where I removed an LP Water Heater recently to free up space for a more spacious layout of water closet, lavatory sink and shower unit. The roof is a 3/12 pitch and the vent leaked so I figured that going electric would solve the troublesome vent leaking issue on the roof.

Planning a "dog house" to house an electric water heater. This would be a room attached but not interconnected to the bathroom. It would be of stick (2 x 4) construction with a traditional asphalt roof and vinyl siding and wood floor over joists to match the cottage construction. The bathroom will be heated with baseboards for chilly but not winter usage, but the dog house would not. The cottage plumbing lines will be drained along with the water heater for freezing temperatures before winter sets in and traps filled with RV anti-freeze. The cottage would not be used during the freezing winter season.

QUESTION: Can I install the electric water heater in this "dog house"? Access to the Water Heater would be from a weathertight exterior door. The copper water lines would be run from this new "room" down through the crawl space and up into the bathroom via the floor. Can the water heater be wired (30-amp circuit) with appropriate wiring paths in the wall, and up into the attic. It would be shielded with armor cable or plastic whips as needed. Should it be on a AFCI circuit? There would be a 2 x 4 wall seperating the adjacent bathroom from the water heater. Is this water heater location acceptable? The dog house would be weathertight. Thanks.