I recently installed a GeneralAire 1099 LH in a 3000 sq ft home, new construction. I was having a problem getting the RH above 30% when using cold water. Hooked up to the hot, RH is now comfortably at 40%. Lots of problems due to an overpowered furnace, but hot water did the trick. I browsed the forum and saw a lot of people asking how much hot helps, and in my case, it was 10% increase just one day after making the switch.