Insulation, Radiant and Vapor Barriers - Blown in through top of wall?

I've heard that if there is access to a top of a wall, (as one might have in a 1 1/2 story house) cellulose can be blown in through the top. The question this raises with me is if holes are drilled in the top plate of a wall every 16" to facilitate the installation of the cellulose, won't this seriously compromise the structure of the wall?
I appreciate any input.

Glenn,
Winnipeg

As far as I know there is usually no load on an exposed top plate. At any rate the holes needed to blow in are only 2 inches diameter. If you do it make sure to use a fill tube and not just a nozzle to avoid settling.

Make sure that there are no firestops or obstructions to keep the insulation from going down. We typically blew cavities using two holes per cavity that would really pack it in. I am not sure about down from the top.

You can blow it in until you get resistance. By using a hand timer you can see how long it is taking. If it fills too fast you know you have some blockage. Also you can take a fish sinker weight on a mono-filament line to make sure that the cavities are open.

Remember that blowing will find any opening including some electrical box fixtures or any opening such as spaces around plumbing.

Jim

The blowers I have used only require a hole that is 1 1/8" or so. If you make holes through the top plate to insulate, when you are done insulating, the holes would best be filled with a fire-rated sealant such as Great Stuff Pro- gaps and cracks- fire rated foam.

Some area require all top plate penetrations to be sealed in this manner to slow the spread of a fire.