Here is a good website to reference for foam insulation:
http://energy.gov/energysaver/types-insulation
Types of Liquid Foam Insulation
Today, most foam materials use foaming agents that don't use ... read more
There is minimal maintenance to keep the water heater running good as new. Here is a quick link to some helpful steps http://www.wikihow.com/Maintain-a-Tankless-Water-Heater