Conditioned attic: Best insulation / ventilation (with standing-seam metal roof)?
In a month, I’m planning to finish the attic of a small cape in Burlington, Vermont (Climate Zone 6) to add bedrooms and a bath through two shed dormers (house is only 24’x34′, thus we need the space of that level). We are planning to do closed cell spray foam for the ceiling and walls and to probably do ZIP sheathing with a new standing seam metal roof (heating system will be hydronic baseboard). The current ceiling rafterss are only 2″x6″ and the walls are only 2″x4″, so I assume that we should pad them out with something deeper, like 2x10s on the ceilling and 2″x6″s on the walls. After spending many hours reading these blogs and articles, I’m questioning our plan and wondering a few things:
1) Is this a good plan??!!!
Do I need air ventilation channels either below the metal roofing or between the sheathing and spray foam?
Would a whole house ventilation system help resolve any risk of moisture issues?
What type of underlayment should we use over the zip system?
Is there a minimum roof slope that we should hit?
Is closed cell foam the right choice? If so, how do we insulate the rafters?
Are there any other considerations that I’m not thinking of?
Thanks so much in advance!
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