Provent 14 in. x 4 ft. Rafter Vent

Yes and no, we do not sell them as a vapor barrier (when I think of a vapor barrier I think plastic sheeting to cover entire area). However, if you do not leave 1" gaps between individual vents in a cathedral application you will have water build up and it will travel to the lowest point. So it will act as a vapor barrier between joists in cathedral applications - meaning a run of vents from soffit to exhaust vent at the top your roof if you do not leave spacing between vents. We do recommend 1" spacing between each vent in cathedral applications unless using a spray foam.

open cell can be sprayed against the roof deck close cell has to be vented... not sure if this product will hold up to the weight

it is very thin as an insulation barrier

Yes you need these with insulation batts. They allow air to move from your soffit vent through to the ridge vent. If you don't have them the insulation batts will block the air movement.

As the vent sits on the under side of the roof and the insulation below it, I think gravity works in your favor. That is unless you really pack the insulation in, but in that case, highly packed insulation would reduce it's r-value.

I believe it's plastic which would have insignificant R-value.

No. Use wire batt supports.

No it is not better, it could then drip on your ceiling. The reason for the one inch spacing is so that the moisture travels out with the air that is moving from soffit to ridge vent. All houses have some type of moisture in the air, which comes from showering, bathing, cooking, or a new house drying. If you have further questions please call 866-240-4933 then select Retail.

Yes the product will hold up to spray foaming, just apply the spray foam in thinner layers. We do have a new product called a proVent baffle which we made specifically for spray foaming. It is the same material however it has additional features - it has cones which help to keep the 1" of airflow, it can be used as a vent or a baffle (baffle means it attaches to the top plate as well as the roof deck and truss). These will be hitting some retail shelves and websites in fall. You can call us for more information 800-666-8191.

Typically I would say purchase Windblock - however there is a shortage of product until February 2021. Your next best thing to do is roll up in-faced fiberglass insulation and tuck between the toplate and the underside of the vent. This forces air to channel through the vent and will prevent your insulation from being blown away from your outside wall (causing cold spots on your ceiling in the winter). Call 866-240-4933 select Retail if you have questions.