Thanks c526 for the tip on putting something under your plants to insulate the plants root zone against sitting on the cold garage floor. I put a VCR tape under each one and have seen improvement. Plus I finally found a use for those old tapes I couldn't bear to throw away
If you can find some rigid foam , or Styrofoam it will work much more effectively. the common white packing Styrofoam would be a big step up from what your using now, the rigid house insulation would be even better. having the foam raised off the floor with spacers would be the icing on the cake.