Have run into this a couple of times within the last few weeks. In an effort to reduce infiltration/exfiltration of air to save energy and improve comfort, the homeowner in one case injected expanding foam into the boxes and in the other, tightly stuffed pink fiberglass insulation around the recptacles/switches…an illegal practice creating a serious fire hazard. Some people have no fear of electricity! Pity!!!
I have found this situation occasionally over the years with the worst period being the first energy crisis of the mid 1980’s. I found foam installed in boxes by a “professional” airsealing franchise in the last city I worked in. I called the only local electrical inspector I knew (reportedly the toughest in the small province of New Brunswick) and within 4-5 months the local company was out of business. The two Atlantic Canada franchisors who conducted this practice were out of business within a couple of years.
Do you check at least a few boxes for this or along side the boxes for wall insulation?