I would like to re-insulate (using my existing insulation) a portion (for right now) a part of my attic (ceiling over my bed room). I wanted to simply lay "aluminum foil" like Reynolds Wrap for an example on the ceiling of my bedroom from the attic (shinny side down) to simply reflect heat coming up to the ceiling back into the room. Then after laying the aluminum foil down, I want to re-install my insulation (either cellulose or open face fiberglass) on top of the aluminum foil. Am not sure, but I think the aluminum foil might act as a vapor barriers for which could be a plus. Right now, I don't have any (vapor barrier) up in my attic and so far, it looks like only cellulose is being used. (FYI: There's plenty of air space for ventilation in the attic). Before going any further, I must state that am NOT looking for the aluminum foil to act as an insulator but to ONLY REFLECT the IR (heat) from leaving the room. The insulation on top of the foil will do the insulating. And yes, I do know about Reflectix bubble reflective insulation but don't want to go there. So, what do you think about this idea? Thanks.
Scotty ~ Louisville, Kentucky
Scotty, you are absolutely correct that a reflective radiant barrier in your attic can improve the overall energy efficiency of your home. While mass insulation, like fiberglass or loose fill cellulose, only slows down heat transfer from the warm areas of your house to the cold areas, a foil-like barrier can actually reflect heat back to its source, which is why those thin emergency space blankets are so effective at keeping a person's body warm.
Without getting too deep into the laws of radiant heat transfer, we can find many everyday examples of reflective foils preventing heat loss, for example covering a hot casserole dish of food with aluminum foil helps keep the food warmer, for a longer period of time, than simply leaving the food uncovered. That being said, I do not think that a standard aluminum foil is the right product to use in your attic. The rolls of regular aluminum foil are narrow, which means that you will have lots of seams to deal with, not to mention that the product tears way too easily to be successfully attached to your attic rafters with a staple gun.
There are lots of heat-reflective products that are manufactured specifically to use in a home's attic and should accomplish your goal of keeping your house warmer in the winter and cooler in the summer. Most of these products are designed to be attached to the rafters or ceiling joists in an attic and can be installed directly over the existing insulation. This means you don't have to remove, and then reinstall your attic insulation (a very messy job), and some of these products are pretty reasonably priced. For example, a 500 sq. ft. roll of EcoFoil Radiant Barrier is only $74, while covering 500 sq.ft. of attic space with Reynold's Heavy Duty Aluminum Foil would require purchasing 10 rolls at $5 a piece, for a total of $50. While there is only a small difference in price, the two products are very different.
I encourage you to do some more research for reflective radiant barriers that are construction-grade, and I applaud your efforts to increase your home's energy efficiency and comfort level. Good luck with your project and thanks for checking in with us at reliableremodeler.com!