I recently drywalled an attached two-car garage (walls and ceiling).
This left the attic area unvented. I installed two 4"x12" soffitt
vents on both the front and back of the garage (total of 4). These
will provide air input into the attic. I also have two 12" square
vent boxes for the top of the roof. I haven't installed them yet as
the shingles on the garage and house are in need to be replaced, which
I'm planning on doing in the fall. I'm apprehensive about installing
the roof vent due to water leakage until the new roof is installed.
I understand that venting a roof prolongs the life of the shingles,
but since they are at the end of their life, would it really hurt to
wait until the fall. Would the new soffitt vents allow for enough
cross ventilation? BTW, when I installed the drywall and new attic
insulation, I left the cavities clear of insulation where the new
vents are installed to allow for the air circulation.