I know the thinking is in favour of heat, but there are so many new products coming on the market designed to operate at 30 degrees, or less.
About 30 years ago Amway " broke the mould" and brought out a soap powder designed to run cold and with no bulk added bulk. From what I remember, it worked pretty well.
In spite of successful trials with all of these products, psychologically I still feel happier with heat, but it's good to know that we can get a result when no heat is available !