I've been wondering about this for years. We have a 800 sq ft basement that has insulation between the rafters which support the main (ground) floor of the house. The fiberglass insulation batts have a reflective surface on one side. Here's the important part - the reflective face is pointing DOWN into the basement space rather than facing UPWARD toward the ground floor living space. This seems wrong to me. Bear in mind that the cost of heating our house in the winter is 4 times the cost of refrigeration in the summer.
Aside from the thermal (radiant) considerations, our wireless internet router and a wireless repeater are located in the basement. From what I've read, any reflective surface will reflect the radio waves thereby reducing wireless data signal strength and throughput where all our electronic devices are - on the ground floor.
Should the insulation be taken down and reversed? It might be easier just to try to strip the reflective paper off of the batts. And, if the reflective surface won't really do much good in basement rafters, I might as well just strip it off. Thoughts? Advice?