The Insulation Bamboozle

Speaking of hot tubs…people always ask me how much insulation is needed to hold heat. There’s evidence that an R-30 factor is enough to thoroughly insulate the shell. One inch of foam gets you to about R-7 so just a little over four inches is enough in most cases. I get a kick from some spa experts that talk about ‘their spa’ having 12-20 inches of foam at some places and ‘isn’t that great!’. Personally, I’ve always wanted to ask that salesperson how they explain the 4-inch thick cover on top of their spa. Heat rises so the cover is far more important than being solidly encased with foam. How much foam is in your attic?

—Max