I have also been researching vent blocking for trusses and I've seen a number of ways to do this both in practice and what is available within the code books. Specifically blocking over braced wall panels becomes more critical and necessary but even for non-braced wall segments there is the possibility of truss roll over and I would highly suggest blocking in all situations.
Raised heel trusses further complicate the matter. A number of resources I have found online that were interesting:
The SBC has a fairly lengthy discussion on heel blocking at this paper:
http://support.sbcindustry.com/images/technotes/T-HeelBlocking08.pdf
Raised heel trusses with large heel heights are given a "truss block" treatment.
However, APA paper SR-103A (2014) goes into some detail about using only the wall sheathing extended over the top plate in low wind speed areas.
The USDA has done some testing here:
http://www.fpl.fs.fed.us/documnts/fplgtr/fpl_gtr214.pdf
The heel blocking/bracing at heels of raised/energy trusses becomes more of an issue when a shearwall or braced wall panel is located beneath that segment of the wall line.
An article in the SBC Magazine:
http://www.sbcmag.info/article/2015/truss-blocking-panels
The 2012 IRC:
http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_6_par055.htm
A paper that sums it up quite nicely:
http://smartgreenbuild.com/blog/download/519/
This was an interesting paper I have never seen before even though I subscribe to this publication:
http://www.structuremag.org/wp-content/uploads/2014/08/C-StructPerformance-Martin-Aug101.pdf
Raised heel trusses further complicate the matter. A number of resources I have found online that were interesting:
The SBC has a fairly lengthy discussion on heel blocking at this paper:
http://support.sbcindustry.com/images/technotes/T-HeelBlocking08.pdf
Raised heel trusses with large heel heights are given a "truss block" treatment.
However, APA paper SR-103A (2014) goes into some detail about using only the wall sheathing extended over the top plate in low wind speed areas.
The USDA has done some testing here:
http://www.fpl.fs.fed.us/documnts/fplgtr/fpl_gtr214.pdf
The heel blocking/bracing at heels of raised/energy trusses becomes more of an issue when a shearwall or braced wall panel is located beneath that segment of the wall line.
An article in the SBC Magazine:
http://www.sbcmag.info/article/2015/truss-blocking-panels
The 2012 IRC:
http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_6_par055.htm
A paper that sums it up quite nicely:
http://smartgreenbuild.com/blog/download/519/
This was an interesting paper I have never seen before even though I subscribe to this publication:
http://www.structuremag.org/wp-content/uploads/2014/08/C-StructPerformance-Martin-Aug101.pdf