Two questions:

1:  Do I have double bubble put under the metal to solve any condensation issues or is ridge/soffit ventilation enough?  I’m paying to have this done so I pay for not only product but also the install and I’d rather not have it if condensation won’t occur.  Cost is $3200 I could put into something else.

2:  I was thinking of putting Tyvek Home Wrap between the metal siding of the building and the girts to help with wind drafts, it’s pretty windy here so having another barrier would be good.  Any problems with that?

Details:

I’m building a metal pole building in Maryland, Zone 4A, 30x60x12 in size that will not have any extras in terms of insulation on the inside at the moment.  Metal directly on the purlins.

I’m spec’ing the building with 60ft of ridge vent and i’ve asked for 12″ overhangs, however it seems like 18″ may be preferred to get the sq inches I need for the 1:150 ventilation in the soffit.  Owen’s Corning says I need around 800 sq inches of soffit vent and about the same in the ridge vent.

Building’s first year use:

It’s use for the first year will be tractor and implement storage and I don’t plan to do anything in the way of insulation.

I may pour a concrete pad during the first year and would use a vapor barrier under the concrete.

Following years use:

In following years I will install a vehicle lift, put metal on the underside of the trusses and insulate with blown insulation (fiberglass or cellulose).  Probably box in a small part for office space (10×15).  Will add maybe a woodstove for the big area and a minisplit for office part.

Thanks for any advice, I have looked through some building science papers and am a little confused on recommendations from that guide that my region doesn’t need additional vapor retarder? for a vented roof?