Thanks for all the great info to date.

One last question. Can I use leftover 'number 15 felt' as exterior paper over sheathing and under siding (house wall). ...or is it 'waterproof' and will create an issue with fibreglass insulation in the wall? Will the felt act as un unwanted exterior vapor barrier that doesn't allow moisture to escape?

How does it work on a roof? If the insulation bats are stuffed between the roof rafters and plastic stapled over then wouldn't moisure be caught in between the felt and the vapor barrier?

Thanks for all your patience with these questions. An unexpected early snowfall has slowed down my project. I want to get the exterior finished as soon as possible so I can tackle the interior with unfrozen fingers!

 

Sorry, I forgot to add this inquiry. At Home Depot there is a roll of thinner, lighter weight black paper. The roll is about half the diameter of the felt. Is this what is usually used for sheathing under siding?

 

Use building wrap (Tyvek, etc.) instead of roofing felt under siding.
It is made for it.
Mike