Root Zone Heating and Insulation of Greenhouse

When I intended to use my greenhouse mainly for storage I installed a double layer floor over the native dirt instead of using gravel.  I wanted a surface I could easily clean.  The first layer consists of 3/4" thick mats of recycled tire rubber which had been used as an athletic floor in a gym.  Over this I placed an indoor/outdoor carpet that extends from wall to wall.  This flooring has proven resilient to flooding.  I recently learned that insulating the floor of a greenhouse is a good idea since the earth itself can suck a lot of heat energy out of the greenhouse.  The thick black rubber floor makes a good insulating layer.  Years ago I purchased a large amount of mylar faced bubble insulation which was on sale with the intent of using it in a projected construction project that never was realized.  I have been able to use this material in the lower wall areas of the greenhouse where transparency is of no value.  Because it has both insulating properties and is reflective, I plan to use it under my nutrient film trays to retain the heat provided by a 40 foot seedling heating wire.  Adding and retaining heat are my chief concerns at this time of year.