Wall Top Plate Insulation

chronojosh

I searched the forums and can't seem to find the answer I'm looking for so here it goes. I am adding insulation to my attic and I currently have R-30 fiberglass batts in between the ceiling joists. I want to add R-30 fiberglass on top of that and run it perpendicular to the joists. The area I am having trouble with is how to add more insulation to the top of the wall plate where it meets the eaves of the house. I don't want to compress the new R-30, and I do have rafter vents installed. Could I just fill some bags with insulation and stuff it in there? Is there any value added? Hopefully the attached picture helps. The blue circle is what I am trying to figure out how to insulate.

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joecaption

http://www.energystar.gov/index.cfm?...y_rafter_vents

Gary in WA

In the above link Joe gave, if you down-load the rest, they used f.g. in garbage bags at open studs and under knee-walls, which is fine. Yet where it should also stop incoming air movement at the exterior wall line, they say just use an air-permeable f.g. batt, without the bag! F.g. should not touch the roof sheathing (conduction) at the baffle sides yet something should protect it at that soffit end from wind-washing (degrading the R-value). Night-sky radiation will wet the insulation in contact with the sheathing; http://www.buildingscience.com/docum...bout-diffusion

Best is to use homemade baffles of foamboard (stopping all air movement to your f.g.) pp.72; and add rigid f.b. stacked at the exterior wall line- pp.71 (Option 3); http://www.buildingscience.com/docum...n-roof-venting

Another opinion on f.b. over wall at the slope junction; http://bct.eco.umass.edu/publication...o-save-energy/

Gary

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Windows on Wash

Just spray it with the same stuff you are seal the top plates with.

+1 to Joe and GBRs suggestions too.

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