Water Storage Building Design & Ventilation
I am constructing an off-grid residence in phases about 30 miles SE of Atlanta, GA (Zone 3).
I’m currently constructing a 16X24 structure to house two (2) 1500 gallon water tanks, as well as, provide storage space for garden tools and equipment. The tanks are filled by a Grundfos SQFLex DC pump powered by a 1500 watt PV array. I intend to use a single 215 watt PV panel to provide DC power for lights and ventilation.
The walls will be 2×4 insulated by an exterior layer of 1″ XPS and batts between the studs. The roof is a 2×8 rafter configuration to permit the tanks (5′-4″ X 10′-8″) to fit inside the structure framed with 8′ high walls. I plan to insulate the roof with a layer of 1″ XPS and between the studs with R-19 batts. Due to design and other considerations, the walls need to be only 8′. Comments on this system are invited.
The exterior will be a combination of cement fiberboard siding and polar bark siding . I plan to use 1″ X 2-1/2″ vertical furring (1′-0″ O.C.) behind both the bark siding and fiberboard.to provide a continuous air space between and siding and the XPS (foiled). The air space will be screened at the bottom and will discharge into a screened vented soffit. The 1″ air space will be continued across the roof from the soffit to a vent ridge. The roof is metal.
The building will not be used for any thing other than water storage and tool/equipment storage, thus there are no windows and only a 6′ wide double door at one end that would rarely be used. Water will be flowing through the 1-1/2″ fill line during the day (when the sun is shining). I do not plan to heat this building, but rely upon the building envelope/insulation system and any thermal benefits the 1500 gallon water tanks may contribute (?). I would like to hear from the experts on this plan.
My ventilation plan is use a D.C. powered Zephyr in-line fan (http://zephyrvent.com/ )designed to vent battery boxes. This unit consumes <3 watts, thus it will run continuously. It is rated at 6 CFM and based upon my calculations, I should get about 2 air changes per day. I would like to hear from the experts on this. What are the experts thoughts about installing the fan to “draw” the outside air at the end away from the tanks and exhaust near floor level at the tank end. Obviously, this would create positive inside pressure. The tanks would be 12-13 feet from the intake vent. I am in-and-out and do not have ready access to my computer, so I will be slow responding to any questions and responses. Thank You Paul DeMent
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