Asked on Apr 15, 2016

Adding baffles to existing insulation in room over garage

Clay B
by Clay B
I have a room over garage. There is fiberglass insulation in the slanted part of the ceiling. The air behind kneewall can not move up to ridge; hence no ventilation. Is there a method to add baffles (proper vents), or something, to create an air flow from behind knee wall, to ridge. I do have soffit vents under gutters/knee wall area, but there do no good when no venting above. I need ideas on how to get this air to flow. Insulation was installed before drywall, and stapled in. It's about 8 feet of insulation, to trying to force baffles in that length is not possible, besides roof nails are protruding, and baffles would get caught trying to slip them in. Area that I'm trying to create air flow is represented at GREEN arrow in photo.
  2 answers
  • William William on Apr 15, 2016
    So, no soffit baffles to the ridge were installed before insulating! Two ways this can be solved. A cheap way is to install low profile roof vents above the area behind the knee walls. Air would flow thru the soffit vents and out the roof vents. Leave the area below the ridge vent alone - air will naturally rise out the ridge vent. Don't know how long the room is. Do you have access to the area behind the knee walls. This is what I would do. I would locate two rafters (use a stud finder) and cut the drywall out in between them from the soffit to the ridge. If you do not have access behind the knee walls, cut out an opening in between two studs to gain access. SAVE all the drywall cutouts, marking them from where they were removed from. Take down the insulation from the cavity you opened up. Now you can install insulation baffles in the cavity from the soffit to the ridge. Get some 1x boards and sister them to the rafters to support the replacement drywall. Reinstall the insulation, reinstall the drywall you cut out screwing it to the sistered 1x's. Some mesh drywall tape (it's sticky), and drywall compound over the seams. If the room is long you may need to do a few of these. Hope this helps. Good luck.
  • TipTopHouse TipTopHouse on Apr 15, 2016
    if you have some access to either the knee wall area or the upper attic area this can be done with a little effort. Using short PVC pipes that can be slid between the roof sheeting and the existing fiberglass. Put caps on one end so the PVC pipes do not dig into the insulation. Once three or four have been successfully pushed through the area compress the insulation by pushing the pipes down against the insulation and push up the plastic baffles . Once done pull pipes out and start again in next bay. This is time consuming but with little effort you will have success. The ability to be successful will depend your ability to get into an area to work and how much ceiling area is being covered. If its greater then eight feet, you will have a difficult time using this method, primarily because of the nails catching the foam baffles. If this is the case, you would be better off pulling drywall down and starting over. The only other method that will cure all of this is to have a professional energy audit performed, take advantage of the rebates that should be available in your region and have the attic sealed using spray foam.
    • EB EB on May 05, 2020

      I have the same situation. Curious if leaving the pvc in place worked for you. Ive tried using 2x6s laid flat to co press insulation and push up a baffle, but it is very time consuming and the insulation is pushing pretty hard against it, partially collapsing it and reducing air flow. As much more as it would cost, putting 1.5inch diameter across a rafter bay, it would sure be easier!