Q. Can you spray insulation in a house being built during the 9 days? The company is hard to engage and it can delay significantly the construction.
A. Horav Shlomo Miller’s Shlit’a opinion is that adding insulation, even when sprayed to an existing building or to a structure that is being built, during the nine days is permitted in need, since it is not a “binyan shel simcha” or a specially gratifying or happy occasion when done.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit'a