Blown in Cellulose or Batts in Vaulted Ceiling / Scissor truss
GBA Editor
| Posted in Energy Efficiency and Durability on
I’ve been advised against blown in cellulose because the pitch is too great and the cellulose will eventually settle from peak ( http://www.flickr.com/photos/48876863@N08/ ). What is the best practice for insulation for this pitch?
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Replies
Blown cellulose always fills around framing much better than batts. If you do a loose fill of cellulose, like in a flat attic, then it will settle - it's designed to settle, which is why the R-values given for the product are for settled density.
If you do a dense-pack blow, filling tightly from ceiling to roof plane, then it will not settle since it will be installed to at least double the settled density. Even with loose-fill, if it's installed deeply enough at the peak, gravity settling will reduce the eventual thickness but not leave a gap.
The problem you're going to have with any insulation, however, is inadequate thickness at the eaves since you installed inappropriate roof trusses.
I believe you asked a similar question before and the answer still the same. You do not have Healed or Energy trusses to allow continuous and adequate blown insulation in your attic. At this point you are better off using spray foam under the decking and rigid foam above the decking.