Joe,
some more experienced folks will be chiming in about tyvek locking in moisture, the numerous thaw/freeze cycles and I wonder how much snow depth you expect to experience during the winter.
folks, please double check my math but
~6" of non-compacted snow is roughly 0.6" of rain equivalent on 160 sq foot roof (20'X8' like a collapsed 2720 model), assuming a collapsed TM and not an open one..a couple autumns ago we were camping outside of Telluride Colorado and received an inch and half of wet snow overnight and it was a bit treacherous closing the TM in a semi-controlled fashion.
or ~13,824 cubic inches of water per 6" of non-compacted snow (240"X96"X0.6").
the volume of a gallon of water is 231 cubic inches.
so 59.84 gallons @ 8.34 lbs per gallon
or roughly 500 lbs of water per 6" of non-compacted snow...
(IMO) seems likely worth the $40 extra per month. Dave
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