How do I provide intake ventilation at the knee wall where there isn't an overhang?
Here is some guidance for venting a knee wall.
There are a couple of solutions for knee wall applications without overhangs. 1. Use either The Edge Vent (roof-top installed intake) or Vented Drip Edge for intake ventilation but make sure that there is a path for the air to travel above the vaulted ceiling area to the ridge vent (exhaust vent). In many Cape Cod style homes with knee walls the vaulted ceiling portion above the second floor room is densely packed with insulation. One way to open this area back up is to slide some wooden slats or plastic tubing (a downspout of a gutter could work) up the underside of the roof deck and then flip them on their edge to force down the insulation and create the necessary air space. This process is easiest to achieve if the fascia can be pulled down to give access through to the underside of the roof deck form the outside. Someone can feed the slats from outside while someone in the knee wall area guides the slats up towards the ridge. Once the slats have been positioned it may be possible to slide insulation baffles up in the space that has now been created, similar to snaking wire. The best time to insert the slats is when all of the roofing nails are removed prior to papering and shingling. 2. If the vaulted ceiling portion is too tightly packed and/or you cannot use either The Edge Vent or Vented Drip Edge for intake, cross ventilate the knee wall space using gable vents in the ends of the knee wall area. Similarly, vent the upper attic portion above the room with gable vents, cross ventilating. This will leave an unvented portion (vaulted ceiling) between the two vented areas (knee wall and attic) -- which is not ideal -- but it is better than no ventilation at all. It will help get rid of moisture getting introduced to the vented spaces, and it may also help with some of the moisture in the vaulted area. Note: If the roof is being re-decked take advantage of the easy access by installing insulation baffles the entire run of the roof. Be sure, however, to leave a small gap (a 1/8" will do) between the insulation baffles so that moisture can be vented away.