Hi, I just bought a house in Brooklyn , NY that was built in 1920. It is a semi attached house so only one side had windows. I'm doing a full gut out job on the house and I wondering about the foam insulation. From what I understand it is an energy saver and its worth spending the extra $$ even though i'm working with a tight budget. IS that true? When I call the Insulation contractors they offer a few different once 1- High Density 2- low density 3- Cellulose. Which one would make more sense? And how do I know what the contractor will be using? Also do i need to use this insualtion on the side that is attached or should i use a diffrent type of insulation to save some $$. And last what is the average price per SF.