Same as my garage. They have these plastic trays that keep the air flowing between the insulation and the roof. So if you have soffit venting on the sides you'll need these plastic trays between the roof trusses or the air would stop, because the insulation would stop the flow of air.
Unobstructed can basically be defined as the 'opening' in the vent... soffit venting and those plastic roof vents do have an opening rating or dimension on them... some plastic roof vents are 50 or 92 sq.inches, and typical 12" wide soffit venting is about 5.8 sq.inch of venting per lineal foot...no harm in a few too many vents either... you can also use end gable vents too...
The only other heads up, is that the National Building code wants 2.5" between insulation and the roof sheathing, but most of those styrofoam spacers are 1.5" (i think they are made for a US code). 1.5" is better than no airspace, but an inspector could give you hard time... again this may not be an issue for you depending on where your insulation is, in particular on the upper floor...
Unobstructed can basically be defined as the 'opening' in the vent... soffit venting and those plastic roof vents do have an opening rating or dimension on them... some plastic roof vents are 50 or 92 sq.inches, and typical 12" wide soffit venting is about 5.8 sq.inch of venting per lineal foot...no harm in a few too many vents either... you can also use end gable vents too...
The only other heads up, is that the National Building code wants 2.5" between insulation and the roof sheathing, but most of those styrofoam spacers are 1.5" (i think they are made for a US code). 1.5" is better than no airspace, but an inspector could give you hard time... again this may not be an issue for you depending on where your insulation is, in particular on the upper floor...
ak
This kind of stuff is simple for people that do it every day. Thanks for the info.
