6 months ago we bought a 100 year old shingled house in Boston, 3 stories with a slate roof. It has adequate insulation in the roof and dormers, but nothing in the walls. We're considering cellulose or Icynene - should we be thinking of something else? Given the air leakage issue, Icynene looks good, but we're wondering about the difficulty of adding wiring in the future. We're fine for now since we just updated the whole elec. system and added outlets everywhere, but who knows what an owner in 50 years might need.

Icynene has a higher R-value. Cellulose also does a great job cutting down on airleaks. It will fill up every hole it can get to. Either one will prove a fun job to add wiring later on down the road but will probably be easier with cellulose. You can reuse the cellulose if you have to remove it.

thanks that's helpful. I appreciate your expert opinion!

I am adding a closed cell foam to a house built in 1888 and placing some electric conduit (plastic) in the walls to provide a chase to run wires if needed in the future.
After a lot of research and living in a 100+ yr old house for 26 years, I strongly suggest the foam, but i would use a closed cell slow rise product instead of Icenyne. it has better moisture barrier (wont absorb water) and has a better R value.