Height of Insulation Baffles for Vented Cathedral Ceiling
Hello everyone,
I’ve just finished installing some rigid foam insulation baffles on a new house I’ve been working on. The roof pitch is 6.5:12, and the interior cathedral ceiling is a 3.5:12 pitch. I installed the baffles so they provide a clear path for ventilation to a point above the insulation that’s just below them, but then as the ceiling goes up, so does the insulation. My question is should I have installed longer baffles to get the airflow up to a point higher than the highest insulation to avoid potential wind washing, or is it fine as is?
House is in climate zone 6. Insulation will be r-60 blown in cellulose. I’m installing the poly vapour barrier (also acting as air barrier) on the underside of the trusses as nearly one solid sheet, then 2×4 strapping, than installing my interior walls to that. My hope with this is to minimize air leakage. Unfortunately the truss manufacturer only put in 12″ heels as well, so I will only have about 9″ of insulation just above the exterior walls.
I’ve read many articles about cathedral ceilings on this site but never saw this particular issue discussed. Thanks in advance.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
I'm not worried about wind washing inhibiting the insulation effectivness, but I am a little worried about the insulation blowing around and falling down the chutes to the soffits. I would either continue the baffles up some extra, or install some netting over the insulation to keep it in place.
Thanks for your thoughts Charlie. Netting would be serious pain to install afterwards since there would only be 0-2.5 feet of headroom at best. Extending the baffles might be a better solution if required, or maybe even switching to batts instead of blown in if the insulation would be blowing around.
I agree with Charlie--I generally run the baffles several inches higher than the highest loose-blown insulation.
+1 for extending the baffles higher. I'd extend them a convenient amount (read as "whatever the baffles can be cut to evenly with minimal waste material") on the steeper pitch roof, and I'd probably go up at least a few feet on the shallow pitch section. My thinking is that the shallow pitch area is more likely to have issues with stuff blowing around and possibly getting back into the air channels.
Bill