Blown vs batt insulation for vaulted, non-cathedral ceiling
In my climate (4a), code calls for R-49 in the ceiling. We asked for the roof to be framed so that there’s plenty of room for the insulation. There are two rooms with vaulted ceilings, non-cathedral. The roof pitch is 8/12, but the ceiling joists in these rooms are 6/12. I’ve looked everywhere on the best way to insulate this and batts are what mostly comes up. I did see a similar issue for an attic reno on this site where a response was to put netting on the top and bottom of the ceiling joists to blow the insulation in. However, I don’t know if that was done and how it went. Nor have I seen that anywhere else, so I still feel like we’re blazing a trail here. Our plans are for the attic floor to be covered with cellulose. With its high R-value, fire, and sound rating, it was a no-brainer. However, this also means that these rooms do not leave room for fiberglass in areas where the roof joists pinch down close to the ceiling joists.
Our walls will be filled with mineral wool batts (R-23 in 2×6 studs), which also have a high R-value in a more compact space. We actually pulled our building permit just before code change acceptance in our area so technically we only have to meet R-35 in the ceiling. With that in mind, if I compare the netted cellulose with two layers of mineral wool batts in these two rooms, the batts cost $1,300 more.
Unfortunately, the shape of the house causes some of the corners and sides to not be easily accessible without significantly squeezing yourself between the ceiling and roofing joists and around corners, so whichever direction I go, I want to make sure it’s both effective and solid. We do not want to revisit it later. That alone has made me think the $1,300 may be worth it, but then again, the cellulose will fill all the spaces better and might be more solid than I would think.
So my question is whether its worth the $1,300 more to just go with the batts? Or is it worth blazing this trail with the cellulose? Do those of you in the know see where there may be significant issues that would need to be overcome? Maybe you’ve been here yourself?
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