Replies

1. 
   user-2409187 | Oct 19, 2016 07:17am | #1

   Hot air can't be expelled unless cool air replaces it

   The essential principal is that hot attic air can't be expelled unless there is fresh (cooler) air to replace it. Make sure you provide for a gap between the insulation and the roof sheathing in each rafter (or truss) bay. The soffit MUST be vented to provide for the movement of air. In areas where there is no soffit venting you might want to consider spraying foam insulation into the rafter bays. Foam insulates and takes care of condensation issues. And foam is ex$pensive!

   Gable vents (cross ventillation)  will, generally speaking, take care of ATTIC SPACE, but will not vent rafter bays behind/below your knee walls UNLESS you have functioning soffit vents.  From your description, the ridge vent does not do much...sigh. Ridge vents work in conjuction with soffit vents. The essential principal is that hot air can't be expelled unless there is cooler air to replace it. Absent the first, the second is impeded.

   Mel froscarpentry.com

1. 
   user-6425240 | Oct 19, 2016 09:57am | #2

   Thanks for your reply!  Even if I do foam insulation how would that side of the house be properly ventilated? I saw somthing called smart vent which is a vent that goes under the first couple rows of shingles that's a continuous vent.  Have you ever heard or used it before? 

1. 
   user-2409187 | Oct 20, 2016 12:28pm | #4

   Even if I do foam insulation how would that side of the house be properly ventilated?

   Rafter bays are foam insulated. If there is attic space above these foam-insulated rafters, it is ventillated with gable vents. These allow for the cross movement of air. A ridge vent is virtually useless in this instance, but it won't hurt to install it.

   I saw somthing called smart vent which is a vent that goes under the first couple rows of shingles that's a continuous vent.  Have you ever heard or used it before?

   No...and here again, for this product to function you will need to create and air passage in each rafter bay (with insulation below it). A ridge vent will also be needed. Or, if there is attic space at some point, the air passages you made in each rafter bay end in the attic. Now you can use either a ridge vent or gable vents...or both.

   The essential principal is to not block the flow of air from lower down to higher up. Make sense?

   Mel froscarpentry.com 

2. 
   sawdust_steve | Oct 19, 2016 11:39am | #3

   With spray foam you go unvented. It's a great system but it is expensive.